International Geomorphology Week 2023 – Western Europe

00:02:15 Heleen C. Vos – Dust emission in South Africa and their relationship to land use and drought
00:12:55 Jean-Philippe Belliard – Semi-diurnal vs. diurnal tides: what are their impacts on coastal wetland adaptability to sea level rise
00:22:45 Willem Toonen – Variability in Lower Meuse deposition (the Netherlands) identified from the meta-analysis of radiometric data
00:34:13 Tara Beuzen-Waller – Late Pleistocene-Holocene fluvial records from the southern piedmont of the HajarMountains (Oman): hydro-climatic and archaeological implications
00:44:48 Amélie Duquesne – Evolutionary trajectory of a low-energy river during the Holocene: the Charente River between Angoulême and Saintes (south-west of France)
00:56:07 Matteo Roncoroni – The ecology of a recently deglaciatedAlpine floodplain: the case of the Otemma flood plain
01:04:11 Sara Savi – Proglacial areas: sediment sources or sediment storage? What should we expect for the future?
01:13:24 Natalie Lützow – Global patterns and trends of glacier lake outburst floods since 1900
01:22:29 Simon Kainz – Thermokarst processes in rock glaciers as triggering mechanisms of high alpine debris flows
01:32:45 Daniel Draebing – Cracking and Crumbling – How frost cracking drives alpine rockwall erosion
01:44:15 Alessandro De Pedrini – Chronology and morpho-climatic history of large rock slope failures in the Southern Swiss Alps
01:54:11 Alejandra Jiménez Donato – The potential of long-term monitoring of slow-moving landslides for understanding landslide dynamics
02:04:21 Antoine Dille – Does the movement of a landslide change when a city is built on it? A study of feedbacks between urbanisation and landslide dynamics in the tropics

So welcome everybody um it’s just past the hour this is the last of the I A’s uh Regional webinars this is the webinar for Western Europe and uh this year we’ve Run 10 webinars in various regions around the world and so far um I’ve been looking at statistics so we’re getting a

You know a good uh amount of participation compared to previous years this is the third year we have the iag has run the regional webinars so we’re delighted you could join us again I noticed uh a few uh people in the audience uh uh I’ve been to of this

Year’s last year and previous years but any of those of you that haven’t uh been to these webinars before essentially the idea is that we uh consult the national scientific members of the iig so there the national associations the geomorphology groups don’t in different regions of the world and we asked them

To provide us names of the brightest outcoming geomorphologists and then uh from their recommendations we go out and invite and cons construct a program are bringing together all those uh different researchers and uh so the idea is to give you a taste of the sort of things

That are going on in you know sort of research is going on in different areas of the world uh in geomorphology and so we’re covering all sorts of topics from uh from Desert geomorphology to uh to Wetlands to to fluvial geomorphology glacial paraglacial uh all those kinds of things

And uh I’m really excited about the program we’ve been able to put together and I’m really happy that the the people that so many of the people we invited said said yes uh straight away we had a few people say no because they’re in the field I think that’s quite a good excuse

Some people said yes even though they were in the field which is fantastic so I’m really pleased to have such a a great program ahead of us thank you very much for having to be speaking here my name is hel F I used to work at the University of Basel but I

Actually moved this year to stush in South Africa but I’m still working on the project that I will present uh right now which is also in collaboration with the University of Cape Town we started this project last year and we got some interesting results but hopefully the future will uh give us more

Opportunities to continue this research and as a start I would like to do a little recap on dust and why we’re interested in dust and dust might less of aant Topic in Western Europe but I still think it is a bit relevant because hopefully most of you can remember seeing these dust clouds

Traveling over the continent which is uh all dust coming from the Sahara and the reason why dust is interesting is because it small but also generally very nutrient Rich particles so the emission of these particles the transport and the deposition of nutrient Rich particles can have big impacts one important impact for the

Emitting area is that dust can play a role in land degradation because when nutrients are removed from uh land it will of course lead to the depletion of these nutrients and Fs dust can have both a cooling and a warming effect on climate generally cooling uh when there’s dust in the air

It sort of reflects incoming light and it can promote cloud formation but when dust settles on snow or ice it can of course also decrease the albo dust plays a very important role in the global chemical flux especially the feeding of nutrients poor region is an

Important uh aspect of dust one of these nutrient poor regions is the oceans Dusty position in the ocean can feed Aly can then lead to more CO2 absorptions by these Aly but then do can also have a negative Health effect the World Health Organization estimates that there are

Two million deaths per year from air pollution and dust is part of that and that can carry trans can carry pathogens and allergens so the exact effect of dust depends a lot on where it’s coming from that determines the characteristic of the dust and where it’s going and that’s

Why there’s a general interest in understanding what surfaces are emitting dust and what factors uh control this dust emission right so for this reason there has been uh Dusty regions have been studied some uh regions are understood better than others and that brings me to the dust from the west coast of South

Africa the dust here had been observed by a study in 2017 and we can also observe it oursel now if we look at this uh beautiful satellite image however it has not been further studied so we don’t really know what kind of surfaces are emitting this dust and what’s controlling this dust

And this is something that we wanted to address uh with our project our aim was to identify the spatial and temporal variation of this dust emission and determine its controlling factors that we identifies the source points from 2000 to 2021 using modus satellite images which is an example

Given on the right so when we say dust Source points it means that we try if we look at a dust Bloom like this that you try to find where is the dust exactly coming from it’s not just one region where the dust is where it’s exactly

Coming from and then we combine this data with meteorological data and uh land use data and land cover data which are achieved obtained by satellites so let’s have a look at the first results so over the last 22 years we found 569 dust Source points I showed them in

The graph on the right you can see that most dust comes from the a region very close to the coast and some more Inland dust sources let me see if I can do laser pointer here you go and if we look at the monthly variation there’s a dust season between April and

September with sort of peaks in June and July this is in South Africa the winter and then the middle shows the wind row of the wind conditions during these dust events so there’s General North to Eastern winds the northeastern winds can be linked to the so-called Burgins in this region Burgins means uh

Mountain winds in afcan and these are winds quite dry winds that blow from the interior of the continent to the coast so we can see that there and these winds are very characteristic they generally occur in the winter so I have sort of Winter Winds that cause winter

Dust so far it’s quite um normal let’s say but then if you look at the dust sour Point counts per year then we see something strange because up to well up to maybe 2016 it fluctuates a bit with no dust in uh 2012 it goes up in 2017 but then in 2020

And 2021 there’s a tripling in the amount of dust sources the data shows a big increase in the dust Source points over time and when we see a big increase like that there’s sort of basically two explanation either is a change in wind velocity so there’s more wind or there

Is stronger wind or there’s a change in the emissivity of the surface so something’s happening on the surface that causes this big increase in dust since I’m limited in my time today I will Fast Forward a bit and that we did not see a significant change in the wind

Velocity so this makes us think that there’s something happening on these surfaces that causes big increase in dust that get the question what types of surfaces are emitting dust and how did these surfaces change over time to give this increase so as I said before we would

Look at the L cover of the Dust Source points we used the uh length cover data set that is derived from Sentinel data I gave an example of this uh or what this data set looks like on the on the left it’s a very high resolution data set so

You might not see all the all the details of it but an important thing to see is that there’s a big purple area which are succulent kuu sh PLS this is a very um typical and very beautiful biome in this region and what we then did is look for

All the dust Source points what the land cover is from the areas that they’re coming from well doing that gave us the results on the right we see that most of the Dust comes from shopland areas which is not a big surprise since this is such a prent

Land cover in the region but second case goes to mining areas there’s a lot of mining going on on the coast this is generally diamond mining and heavy mineral mining such as zirin and there’s a lot of um dust coming from be regions these are regions that have very little to no vegetation

And not are not really um Modified by humans let’s say however our question was of course what is causing this big increase in dust so then we go back to the picture that we show or the graph that we looked at before with the dust Source points per

Year but then grouped according to the lens cover typ and what we saw is that uh for 2020 and 2021 the biggest increase in dust came from the succulent Gru shrub L lens cover this L cover increased in a Sevenfold in amount of D Source points there was also a doubling of the

Emission points from bare and Mining surfaces so this is very interesting what made these uh sh LS so emissive in the last two years and we think that this is related to a drought that has been occurring from 2017 to 2021 the graph on the left shows the

Rainfall and the end VII and the last five years there was a drought uh which also leads to um sort of a decrease in average um uh n and it’s important to take into account that it’s these consecutive years that for each year lead to less and less vegetation that destabilizes

The soil there’s also grazing going on that I should mention which could be of influence there’s a lot of stock farming and the reason why this Dr is important it’s because uh a further decrease in precipitation has been predicted by the ipcc so this is not an

Exception this can get a stronger over time so the question is will this develop as a more as a dust region and there’s also the loss of soil and fertility with this dust emission so we should also wonder what the chances are for this lens to recover for the uh

Vegetation to come back let’s say so these results I think raise more questions than they answer them an important question is of course what about the dust from this the mining dust what about the influence on the ocean Etc so we submitted a research proposal on this topic and then hopefully if it

Gets approved I uh can give many more presentations on this topic so thank you very much uh so good afternoon everyone my name is Jean Philip Bia and I’m going to talk about Co W adaptability to cver rise and specifically what are the relative impacts of semal versus Jal tides in

Driving this um Coastal weight adaptability so um yeah first of all to give you a bit of context um as you may know Coastal weight LS like T Marsh and Mangrove they show viability in the way they adapt to Silver rise on the global scale so there are regions such as those

Two that I’m showing you on this global map that are notable hotspots where these wetlands are already showing signs of submergence driven by seev Rise but there are also other regions where this white PLS instead are able to build their elevation at rates that are equal or if not exceeding the rate of

Relative C rise and so identifying the factors that control This Global variability has been a yeah long-standing topic of great scientific interest and previous studies uh have shown that uh this variabil variability stor is actually mainly controlled by uh a few environmental conditions so one is the rate of relative silver rise itself

The other one is the suspended sediment concentration so by that I mean the supply of sediment to the weight L uh and third is the ti range and speaking about Tides another important tide characteristic that varies on the global scale is the fact that Tides uh exhibit a variety of

Patterns worldwide as you can see in this global map so patterns ranging from subal patterns uh characterized by two titer ccle in a part today a bit more than day all the way to journal pattern with only one tile cycle per day and despite this feature of the ti is an apparent feature

It’s well noticeable feature all these previous global scale assessments that I’ve mentioned uh did not consider this environmental condition and so this actually led to the objective of our study which was trying to let’s say explore first and trying to potentially Hil a role of the tile pattern is

Driving this Global variability in in weight and adaptability to C rise and so to answer this research question uh we use two approaches so first we carried out the meta analysis so from the literature we compile data on obser rate of wetland elevation change uh for nearly 400 sites um

Scattered around the globe as you can see sorry in this map so this site comprise both tidal Marsh and and Mangrove and uh this wand elevation change were obtained uh by uh the So-Cal surface elevation table which is uh in the Wetland Community a wellknown well established

Like a standard method to monitor change in elevation of both Mangrove and Marsh platform and in addition to that we also uh retrieve values of this uh global scale driver of Weighton ad adaptability that I mentioned previously so we first derive the local rate of volatility rise for every of the

Sites based on tib records uh the um say suspend sement concentration in the nearby Waters uh so that uh we actually obtain those from satellite imagery the local uh tider range and lastly our newly investigated Factor the tidal pattern which here we quantify using the form factor uh which as you

Can see uh in this slide is the the ratio of the um I will just use the laser pointer so it’s the ratio of the amplitude of the two menal constituents over the uh amplitude of the two men semal constituents and then using some multi- Diet uh statistical Technique we try to

Assess the relative influence of each of these predictors and we can see that the tile pattern yeah despite being the least important predictors still expand around 20% of the weight L elevation change globally observed but now if you look at the So-Cal weight L elevation balance which is uh the rate

Of weight L elevation change obtain from this act technique minus the rate of relative sver rise that you derive from tight gold records and that a measure that really tells you whether or not a wetland can keep Pace with C rise you can see that this time the T pattern is

The third most important predictor and with relative influence nearly as much as that of the siment concentration uh then to assess which of these tal pattern actually coincide with Wetland vulnerability to Silver rise we looked at Wetland with elevation deficits so those are weight L for which

The elevation gain is lower than the rate of Relativity rise and you can see that those sites predominantly occur uh let’s say under uh Journal ties so this first let’s say uh global observations indicate that the tile pattern is an important determinant of this weight L elevation change and the

Balance with cev rise so then in a second approach we carried out model simulation where we try to further explore the distinct effect of sem versus L tides in driving uh the sediment acation response of a weight in particular marshes here and here is the first set of results uh

You can see on the Y access the So-Cal freser rate of Rel cver rise for M Survivor so that’s in other word the maximum rate of cver Rise that a marsh can withstand so above which it will convert into yeah bare tidal flat or open water as a function of sediment

Concentration uh and tid range scenario and you can clearly see some uh relationships so the higher the sediment concentration and tyes the higher the rate of silver rise the mash can withstand and that is a result for the case of sem ties um now if I superimpose the result

For the case of the dunal ties you can see that regardless of the scenarios of tal range and sediment concentration this predicted uh faal rate of relative sise is consistently lower so this tend to indicate that the mar that are forced by dunal ties are actually less resident to se level rise

So why is that why do we get um such results uh if you look at the sediment Dynamics um comparing that for marsh po by semal versal Tides uh for a time scale of of a day of a lunar Day so a bit more than a day it’s 24 hours and 50

Minutes uh you can already get some insight into the mechanism at place so basically like a March that is forced by two subal Tides as compared to a March forced by Oneal ties during a lunar day will result in two versus one um inundation events and since each of

These inundation events introduce High suspended sediment concentration that subsequently decrease because of the stting of the sediment these two semal Tides will result in a higher net elevation gain as compared to the single Donal tide even if that dunal tide has a longer inundation period And so this indicate that dunal Tides actually

Promotes lower sediment accretion than semal ties and hence the reason why this marshes and weight and Mangrove caused by Jal tides are seem to be less resilient to c l rise so to conclude uh we have seen that the T pattern despite T now being overlooked environmental condition is

Actually important driver of cotile weton adaptability to sea level rise um and actually through this explorative study the H was also to um stimulate and encourage further research uh because we believe that uh this title pattern can also affect other key whel ecosystem function and services such as

Those that are listed here because yeah those processes those services and functions they are to some extent also regulated by the ination regime of the ties and if you want to hear and learn more about these topics uh feel free to look at our latest published paper on on

That matter voila thank you very much for your attention so yeah I’m going to talk about the low Muse and um I think as oh does it work well doesn’t go to does it go to the next ah it does sorry so as as as most of you probably know um

The the Muse Capt was hit by severe flooding about one and a half year ago and um well a lot has been said about the conditions but um what was expected before is that these type of floods wouldn’t occur before the second half of of the 21st century um and they were

Also not not predicted by our national forecast model so um questions have been raised that is there’s already a rep response to climate change and and can we expect this this more um often to happen in the near future and as part of our our knowledge

Gap so to say um that I think there is a necessity to to study the flal archives for for reference for for periods of Rapid climate change or also periods of uh warming in the past um so what we did is we looked at the catchment or well

The reach of the lower Muse which is in the Netherlands and and what we did there is we constructed a cpdf a cumulative probability density function what that is it is a summation of all the dates we could find that were taken in the fluvial context so every

Dated fluvial unit we GA it from literature mostly literature on flu geology archaeological research but also recent flood management projects we group that data and we uh added all the ages and our uncertainty ranges into a single summation so that gives you a distribution of your dates through time

And that will show you tangent and periodic changes in the formation of aluvial units so there is a particular Focus here on the trends during the holos scene of what changes the river system has gone through in the last 12,000 years these are the results um so oh I

Have to go back to we have about 427 dates get in total so these are these are the results and we grouped our data into three different uh data sets and those are a data set for clastic dates so dates that were gathered from uh clastic deposits dates that were gathered from organic

Deposit so Pete Pete formation um inside a flal contact So within the river flood plane mostly concentrated in abandoned River channels and then we have a third Group which is from both clastic and organic dates and those are change dates so those are the dates that identify major changes in the

Distribution of uh sediment in the river valley so they either identify a change from organic deposits to a classic deposits all the all the way around um now if I go through that record uh step by step if we start by with the early all of scene um we see

That there is very very limited class deposition in the low mu so that’s the the orangey color there so there’s only limited periods where you can see that there is some active overbank deposition or any deposition at all and that’s mainly because the Muse at that time is

Uh very far in entrenched in this Valley so we have the the the end of the younger drest period and we go to the earlier holos scene and we have a change in river system from a braided system to a Meandering system which in sizes about

3 meters so that es when there is a flood or if there is high water that not much sediment is distributed along the valley so all the river activity is constrained in a very narrow space um what we see though are fluctuations in organic content and those are a bit

Surprising because they they coincide very well with um ice rafted deis events on the Northern Hemisphere so these are cool periods so for example the preboreal oscillation the 8.2 event pops up and that’s a bit surprising because normally if you have a cooling in Western Europe that’s associating with

Relatively dry conditions but here we have enhanced Beed growth in our abandoned channels which indicates that there is increased wetness around that time um so this is a kind of conceptual representation of that of of what we think is going on uh at that time is that we might have slightly wetter

Conditions in the Valley of the river because we have um enhanced groundwater levels and that might either be caused by a reduced uh evaporate transformation by the cooler temperatures or maybe also an enhanced um flooding regime and especially in spring because most of the precipitation will fall as snow in a

Slightly cooler climate during the hall scene now if we go to the mid and late Hol scene I group those uh we see a very clear Trend and there’s a very clear uptake in clastic deposits and that has a lot to do with an increasing human impact on the catchment um people start

To clear forest and uh first that that comes apparent apparent with the arrival of of early agriculturalist a bit before 6,000 years ago and around that time we see a an increase in the classic dates and there’s a step up it’s about 4,000 years in the Bronze Age and then again

In the Iron Age um and especially a very large increase in clastic deposition in the medieval period so you see here it’s a reflection of the increasing human disturbance in in the Uplands so um during the Bronze Age and Iron Age there was this were these Technical Innovations which increased the erosion

In the Uplands which delivered more sediments uh to the downstream Valley and um that became so well bad is so extreme that we even have a post Roman Valley fill so from being an in sizing and trenched river system The Muse actually became a slightly a grading

River system by all that sediment which came down the system which came from The Hills first asium and then entered the main trunk Valley of the lower Muse um so as in support of that we have vegetation reconstructions uh for example from the D catchment in northeastern Belgium and you see it’s

Quite consistent uh uh image that first there is a a very slight disturbance of the catchment of the vegetation around 6,000 years ago and then from the Bronze Age Iron Age onwards uh we things really start to kick off and you have a um a

Very active uh mobile system so a lot of sediment gets transported Downstream and is deposited in the Flop planes of the Low imuse Valley then there’s something else I want to highlight right here and that’s that’s a weird weird period it’s about 6,000 years ago and that’s that’s the

End of the mid Holocene Optimum relatively warm period and we have first a a giant Peak there in in um plastic deposition followed by a large peak in organic disposition um and that that peak in organic disposition is is coinciding also with uh a lot of change

Dates so that is much of these dates many of these dates are associated with a sudden change and distribution of sediments across the valley and what we think here is the most likely explanation is is that around this time there was probably a major flood or a

Series of major floods which caused a straightening of the river Channel and causing many oow legs to emerge and so first when that happens you still have some deposition in these abandoned legs but after they become really well cut off and it’s still wet enough and warm

Enough you will start to get Peak growth and that will have a delay probably of a few centuries before that is really disconnected from from the main active River um so I think those peaks in um plastic deposition followed by a peak in organic deposition they are pretty much

Related to the same massive event um such events might be very interesting uh to study further if we want to look at the effects of of climate change and the really biggest flood events that can occur and which are probably most geomorphologically active so the implications and

Conclusions from such uh such a a an overview is that well rivers are self archiving on that past you can if you study them um carefully you can see all kinds of Trends and evidence for high magnitude events uh in the past um and then cpdfs they can provide valuable

Insights in in flal responses to perturbations and those can be climate change that can also be a human uh disturbance to the system but however cpdfs are still in in combined signal so they they combine everything together so we’ve seen evidence of of entrenchment degradation um impacts from climate

Change and human forces forcing and then there’s still research bias so for example not shown here but we have a lot of dates as well for the younger Dr periods and period and that’s because a lot of researchers Focus specifically on that period so we have a lot of dated

Flal units in those specific Windows um and then well the signal combined settlement FL flood regime changes and and Geor geomorphological changes as well um well our research show that that there’s a strong anthropogene geniz of the catchment um we have a change in flooding regime so first we see only

Responses to cooling periods but if you get closer to present day you can see that the river responds to all kinds of different pertubations so in warm periods you can have an amplified uh uh flooding regime but also in cooler periods um and the last the figure

That’s that’s on the right um there are some strong periodicities in the system so for the last 4,000 years but also during the earlier hallene we have a very persistent multi Centennial so about 500 to 800 year cycle in uh deposition or well here this one is non

Deposition so the pee grow um and those are are significant for very long period so that suggests that although humans are have quite quite a strong an impact on on the river system that there is still this cyclicity forced by climate change by the Atlantic climate system

Which is still seen in in those patterns of of overbank deposition um yeah and and last some key major geomorphological events especially flooding can be targeted from such records and that might provide um further suggestions for further research to look at these events when did they occur that they occurring

Fooling periods warm periods or specific specifically during periods of of Rapid climate change and that could all underpin our are coping with with future climate changes as well so that’s it thank you yeah thank you so hi everyone my name is Tara B and I’m a postu at the

University of tubingen and today I will present uh a paper which focus on fluvial records and how they can be used to address question related to climate fluctuation and Water Resources uh during the Bronze Age period in the southern penum of Zar mon so a little bit of introduction first uh in Arabia

Climatic fluctuation alternate between yid and irid period and they are driven by uh rainfall variability related to the intertropical conversion zones and the position of the moonsoon belt and humid period have played a significant role in human environment interaction triggering increasing rainfall flu accusing activity and a denser vegetation cover in north and

Oman in the AAR M uh theid period last roly between 10,000 BP and 6,000 BP and the best climate record we have for this period are the spotm from the OT cave uh but the problem is that there is a 2,000 year IUS in the spell record so

Exactly during the Bronze Age period which is also a period when uh long-term uh settlement evidence of farming and flood management and what we call Proto oist first appeared in Oman so this coincidence raise a question about the adapative response from bones age Society to aridification and reduction

Of uh Water Resources so water acquisition in Oman today relies on groundwater traditionally through an irrigation system based on underground Gallery called Fage uh however the first uh date Fage we have uh is from the Iron Age and it’s still unclear how Bron age Society found enough water to grow crops

And pal trees before so we have two hypotheses uh to explain this right now so the first is that we maybe have a short plal period during the Bronze Age and uh the second one involve the use of huge ditches to collect water from rain and potentially flood so the ditches are

Those big escavation you can see around the settlement but uh it’s still difficult to precisely qualify the erri stress Bron age Society faced and the amount of water they have so to to engage uh this discussion we need to uh know the timing of the rainfall decreasing the timing of the response of

The hro system and the timing of the onset of surface water scarcity and we have several issue for for this is that first the spotm from OT cave start growing at 300 millimet per year so we miss all the data from period which are

Below 300 mm per year which is a lot in a man of course and uh the second issue is the strong uh rain uh orographic indu rainfall gradient that exist between the high mountain range and the low pedmont and uh that problem require local scale studies so regarding this need um flal

Archive are here very useful to reconstruct local hros system response to rainfall variability but they are very rare in om man and so today I will present the first study on late quatar deposit we have for my area which is uh in the southern part of the AAR

Montaine uh so it’s an area which currently receive 70 mm of rainfall per year and the W will study it called weda and it’s a small water course uh which have a water shed of 40 kilom square and it take it Source in a Mesa of low elevation our

Methodology of studying GE morphological survey production of map of quatal information aial and topographic survey realized by drone creation and treatment of DM study of selected section description of the sedimentary fases and sampling for malacological analyzes o dating and radiocarbon the GE morphological survey so that showed that the W disa in size

Neogen glassy made of Mal and three generation of alal ACC imulation were identified cut into a three ter level so T TB and TC the highest t stand four meter above the W bed the medium t- is 2.5 meter above W bed and the lowest one

Is 1.5 above the W bed and we made detailed analysis of Five Section to characterize and date the alal infilling and for the uh ta we have a statgraphic organization that show that the depositional system is mainly dominated by Bread Channel and the section is divide in two part the

Base dead back to the late Place toin so around 26,500 kbp and the top uh date back to the early hosin about 1,500 kbp so prior the hosin Y period and here and I will present all my age dating Min Cal BP in the figure

Uh then uh the Terrace body of TB level have been studied with three section tb1 tb2 and tb3 uh the lower part of tb1 date back around 6,600 kbp and the upper part of the section date to approximately 5,800 kbp and it’s more nwly because of the

Presence of this darker paleo soil units which contain numerous snail and bioturbation the are of molusk of this section present only two species insularis which need shade to to thrive and P desic Tu which occur in river bank or like context uh tb2 section is located within

The depositional lob of meander and tb3 is in a Paleo Channel and both section providers evidence of an hro system which is uh gradually losing energy particularly between 5,000 uh 85,500 K the last uh ter level we have is TC and for this one we only have one age dating about

2,600 and the unit is mainly composed of disorganized eometric material so by following the chronological marker we obtain we can propose a schematic Evolution for theisha so first a phase of incision of the glass SE before 26,500 then a phase of gradation take place between 26,000 and 11,000 so between a Nar

Period and the beginning of the osine uh then the base of TB the the aggradation of ta is followed by two met of incision and this aerogal phase coinci with likely the reactivation of flow Dynamic During the osin humic period the base of TB accumulation is

Dated to the end of the osic period so between 6,500 and 6 ,100 kbp and it organization suggests that the active Channel move gradually to the north and had favor the development of silting area in the distal flute plane where many molusk that like wet and the Shady environment have proliferated and it

Also ConEd with a pannel incision and filling between 5,800 and 5,600 so likely at the end of the unit period and then The Tib race is in size between 5,000 and uh 2,600 BP and around 2,600 BP we have a last alial accumulation characterized by torrential deposit and the incision of TC since

Begun and it’s still ongoing so to sum up we found three phase of alial aggradation and four phase of incision and the TB phase of aggradation occur during the end of the osin human period and was influenced by a by a reduced rainfall which is evident about 5,700

Kbp and the TC level suggest intense rainall and detritic event but we need further date to to confirm this finding so regarding the research question we mentioned at the beginning of the talk uh the study of Risha shed light on two important aspects related to hro system during the olos period and

The B AG so first it it confirm uh that the land area benefit as well from weather condition leading to more regular flow and extended P second also the the end of theid period is difficult to date accurately with flu archive it is clear that what flow were considerably less important at the

Beginning of the early Bronze Age so then um regarding ditches from the Bronze Age here we can see that the dites phenomena happened many centuries after the FL reduction indicating that bronze AG Society did not benefit from a heavier rainfall so then it’s improbable that bronze AG ditches were advantageous

To collect surface water flow and it suspected that ditches were likely meant to collect water from shallow ground Waters that have been recently recharged during the hosin humid period so was shallow ground water the source of the water collected uh by the early Bronze Age ditches that’s the question of the

Rearch project I am conducting right now in Oman with the umel vondel project so I hope we’re going to have more answer in the coming year and if you are if you want more detail about the W Evolution please look at the paper we publish in geomorphology process environment in November 2022 thank

You hello um my name is am duen I will present you my work on the evolutionary trajectory of a low energy River during the hosan the Shon river between angulam and S the study of low energy Rivers has long been neglected by geomorphology in favor of high Dynamic stream this system are wrly

Regarded as Bing and unchangeable and have attracted limited scientific interest this lack of interest is paradoxical because many ordinary rivers in the world belong to this category these um rivers are this lack of interest um this River are associated to a specific Tri po lower than 10 wats per square meter

And a globally stable dynamic in short and Midterm excluding anthropic interventions in the two recent decades increased scientific attention has been paid to this River in connection of river restoration indeed the developments of navigation or the exploitation of hydraulic po have a major impact on these Rivers because of

Their weak slope and lead to huge transformation of their shape and functioning knowledge on the functioning of this hydro system is still very incomplete especially it process and adjustment capacity regarding climate change this is particularly the case for anastomosing rivers in temperate regions for a long time confused with bed rivers

Anastomosing rivers are defined as a type of low energy Rivers situated in low gradient fluit ples these systems consist of multiple interconnected stable channels separated by vegetated Islands nowadays an inventory has not been taken yet even if there a Rel river system with a high Heritage value

However some of an River were recently studied in Central Europe these studies indicate a gradual degradation of yising pattern and their conservation became a major challenge it was th great to discover on the shant River and the Atlantic coast a zone of nearly 100 kilomet long having preserve an aning P

Until few years the anastomosing nature of this River was Unknown by geomorphologist and ional management institution the study focuses on the section between angulam and S within the section the shant River shows a shift of fille pattern in the vicinity of CNAC a discontinuous and weekly anastomus

Pattern on the Upstream section and a predominant s to meing singal channel on the downstream section the flil landscape is marked by high entopic pressure notably since the last three centuries because of the navigation on water Mills nowadays the lack of knowledge on vosis make it difficult to develop

Conservation strategies in a context of climate change and high anthropic pressure Associated to agriculture on new anthropic uses this observation was question about long-term evolutionary trajectory of the low energy rivers and how they have respond to past environmental changes and will adapt to Future one using the

Example of a shant River the primary aims are to one constate hydroclimatic and anthropic factors that can be um that can be um driving forces for Shon reverse changes over the last 300 years using an analysis of geohistorical data to document shter changes in the fluid land

Form of a Shon rer in response to environmental variability over the last 150 years at the level of two special scales fuille segment and fuille Island using a multi-temporal statistic quantitative analysis conducted on four historical Maps understand the long-term evolution of a Shon T in response to AAL changes

On the last Millennium on two study s using geophysical profiles core data and bimetric Survey couple with a leader analysis reconstruction of a recent evolutionary trajectory of a shant River shows a global stability of landforms fille from 1,866 to present the anthropic Factor seems to have played a key role in the

Global permanence of anastomosing pattern in midterm according to geohistorical data engineer in works for commercial navigation water Ms and flood protection seems to have strong local impacts but limited Global impacts the main objective of his engineering Works was to improve navigation but not a massive simplification of the Anastos

Pattern however this global stability doesn’t mean that the weaer as women and change over the last 150 years by focusing on the River Islands which have the most dynamic component of the anastomosing river system sub trajectories of change can be highlight and Quantified if a quarter of the island identify on

1,866 map women’s and CH until now the woming fre quarters are affected by evolutionary process over this period if this Evolution particularly concern the anastomosing sanction that changes are however not uniform over space on time in the earliest period the anastomosing SE experiments a pattern simplification as the dominant process is Island

Disappearance this simplification occurred over a period marked by several 20year return period flute which may have played a key role in reducing the complexity of the anastomosing during the next period the wer pattern experiment High dynamism phase marked by the creation of New Island the division of former Island and The Disappearance

Of some of leaded to a global anastomosing pattern complexification the driving causes of this Evolution are both natural anthropogenic increase of current fluid on the one end and decline of river activities on the other over the recent period the changes are more complex to decipher globally the Shon river is

Experiencing a period of stability but also local simplification of the anastomosis this local Evolution could be correlated to the increase in the number and duration of Summer low water period on two new management practices following the renew of River navigation in order to complete the historical data

Field Works were also performed on Paleo channels on island particular on the Anon site the studies site was chosen because it present a highly developed anastomosis with a very high concentration of pamm on strong archaeological potential the objective of this field work was to characterize the statgraphic organization of the

Islands identify the mechanism of Island construction on De panels indicative of slif of the anastomosis geophysical profile show a course formation interpreted as a no formation iner from bread system on the C feeling corresponding to the recent alial plan of low thickness caused by anastomosing panel field data suggest a flu

Metamorphosis from a high energy breaded system to a low energy anastomosing system which may have occurred around the end of a PL glal based on chronological data from French Atlantic Rivers this anastomosing section persist to the present but in a degraded State the curent anastomosis

Will be a Rel Riv system on the Arc charant radiocarbon de suggest the simplification phase of the anastomosis the second half of a subal affected particularly the secondary chanels this simplification phase coincide with the first indication of netic anthropization identify on the catchment but also this Evolution could

Be the local transation of a global rapid climatic change such as iron Edge called Epoch or 4.2k event according to radiocarbon dates however this first interet ation will have to be refined by supplementary sedimentary and chronological data this study raes question about future evolutionary trajectory of the

Anastomosis of a shant River and how it will adapt to climate change on new anthropic uses local simplification of the anastomosis question because because this type of evolution could increase in the short and Midterm under the effect of climate change and increased water withdrawal for agricultural purposes the river is currently exposed

To several summer low water periods becoming more frequent and longer which could lead to the disconnection of a small anastomosing channels as a result this study highlight several key management issue limiting the cling of anastomosing channels encouraging the activation of recently abon channels on finally promoting the creation of new channel by

Living the Lo however these issues of management of the anastomosis question their compatibility with the issue of New River activities this study highlights lines of research that need to be studed for improve Global Knowledge on the functioning of temperate anastomosis on the local knowledge of a shant River we

Can mention notably the measure of effect of Summer low water period on the local knowledge of a shaant river we can we can mention the study um we can mention also the study of vulnerability of anastomosis to climate change on the impact of flow obstacle and finally the

Study of a potential impact of raran vegetation and its implication in management and preservation of this type of low energy multi Chanel Rivers thank you for your attention thanks Susan for for the introduction so I’m moving away from like classic geomorphology and going into a bit of ecology so um as you all

Know the College of um glossal environments is is tricky because glacial environments are harsh and this harshness is due because of high rates of glacial uh sediment Supply and glacial melt and T creates um events of continuous better working which basically means instability and on and

On top of that you have high turbidity and low water temperatures so we can say that the these environments are dominated by disturbances which basically means that dementing communities and in this case peryon which is basically this layer of algae and an organism growing on Pebbles and Grains and streams the biomass of

Perian is extremely low during the summer because of disturbances and it picks in in fall and spring because the disturbances progressively um attenuate but independently of the biomass which is one thing a pufi and develop in glacial flood Plains and in this research uh we wanted to understand

The drivers that control uh peryon development and and this particularly because uh in these two review papers um Peri in are thought to promote uh vegetation development through ecosystem engineering particularly because of sediment fertilization and stabilization and water infiltration reduction so basically there’s more water flowing at the surface if purifi to LEL

However um tsue papers were review so we wanted to corroborate the hypotheses made in tsue papers okay um my research was focused on T small flat plane here the flat plane of dma Glacier in Southwestern switzland so I’m not going to explain a lot of that because there is this ni

Blog written by my colleague floran Meen and my supervisor Prof sh Lan there’s everything about TOA there’s everything about the researches we have carried out up there so if you want to know a bit more about this this place just visit this this block in my case well I flew many times

Drones I crashed many drones um with the aim of decrypting the physical habitat of fair fighting um and then in 2021 we installed flims uh to decrypt to decrypt to investigate the periton ecosystem engineering and I’m not going to talk about the methods today because I think

The results are much more interesting so if you’re interested in the method just drop me an email or go through the papers associated with this research all right so the first thing we mapped peryon development over an entire Mel season and what TS map shows is the

Number of days peryon was occupying a specific place of the flood plane and and basically what we we found was that peryon development was restricted to the hedges of the flood plane and there peryon developed preferentially in the center of the flat plane peryon did develop but for very

Short periods of time and so we started to ask ourself why first we again we we understood uh with our data that the center of the flat plane was very unstable during the Mel season so basically every day there were events of stream that working while

On the hedges uh the flood plane was 100% stable and this instability versus stability was driven uh by the braiding um dynamics of the trim and in fact in the center of the flat plane the stream kept changing basically on a daily basis uh as you can see from from this image

While on the hedges we had channels that were always there uh Clear Water channels that did not experience any morphological or like eological modification with test data well what we found was okay pufi and developed on the hedges uh because of teres and teres create zones of geomorphic stability

Because they are found at a higher elevation as compared to the braiding system and if these Terraces are drained by Hills lope fed sources uh such as cranial and Rital uh sources well they become OD spots for peryon and also they are perennial habitat where peryon could develop throughout the melting

Season but what was going on in the center um we found that basically braiding intensity uh drove um peryon development in the center and they the breing intensity the higher the likelihood of having shallower and less harsh channels which basically means that peryon could profit of sure Windows of opportunity

Where the channels were more stable and uh with more light reaching the bed but okay periton developed but these were Emeral habitats because in fact the channels kep changing and so the habitat just disappear so this matters because in fact if ecosystem engineering effectively takes place uh it needs time

Uh because purifi purify need time to develop so we argue that ecosystem engineering if if effectively exist is restricted to to Perennial habitats and so we wanted to understand uh this ecosystem engineering effect so in 2021 as I said we installed some flumes in the flood plan of Fatima and

We basically let peryon develop uh for almost 60 days I will just present one Flume here but uh it also applies for the second um but what we what we we saw was that peryon developed and progressively filled the interstices of the SCM bed it reduces

The roughness of the bed and these two things had the consequence of reducing the water vertical infiltration and this matters a lot because um pral margins are extremely well drained and so water easily infiltrates into the sediment Matrix becoming unavailable to vegetation purify develop it cover the

Scam bed is create like um an impermeable layer and water stays at the surface so that vegetation could have a profit and so in conclusion uh well yes the environment of pro the en M of pral margins is Harsh there will be limiting the development development of

Peryon but um there are places where peryon could actually develop these places are Terraces um if there is water of course so is ill slope uh channels and since peryon could develop for long enough uh it could start to engineer the environment and particularly it peryon could increase

The retention of water surface and so yes uh Peri could uh in some ways promote vegetation development um and yeah thank you for your attention uh I think we have a lot of time for questions if you have any so um I’m going to speak about this proglacial area as well but talking

About sediment instead of uh vegetation so um I guess that most of you are familiar with these graphs which shows the paraglacial cycle uh for those of you who are not familiar basically what it says is that we expect uh pick in sediment discharge uh right at the

Beginning of the deglaciation so when the deglaciation starts and then we should expect a decline of sediment Supply to time um that goes beyond the uh the end of decition time then there are some pics in sediment discharge which can be related to either rainfall extremes or anthropogenic

Disturbances uh however there are many studies who um let’s say say um say that this concept is rather simplistic because of course uh paraglacial environment is very complex and the sediment transport is not only uh influenced by water discharge but also so uh we need to know about sediment

Supply and especially the connectivity between the different elements of a landscape so uh actually the the the question is uh will siment supply increase or decrease in future this is still an open question so here I’m I’m going to show you a study from the suen uh proglacial area suen Glacier which is

Located in the central eastern Italian House in the the region of souo um we have used digital surface models which are available since 2005 and aial photographs which are available since 1945 uh here you have an example of the uh difference in elevation uh between 2005 and

2021 of you see that most of the changes of course have occurred in the glacial area uh where most of the ice has melt out but you also see that many changes can be detected uh in the proglacial areas especially into the Channel network but also along the

Morines so uh because I have not much time in this talk I’m going right to the results preliminary results um so we have seen that Moran Supply sediment either a constant rate or sporadically through uh landslides which can be triggered by rainfall um and I’m going to show you an

Example of this portion of the morine but I can tell you the similar Dynamics are also occurring in these locations but also we see that the newly formed channels which follow the glacial Retreat and the reorganization of a fluous system contribute to the redistribution of siment and to the

Erosion of previously deposited material this is occurring right in this location here where the channel That is coming out from this part of the glacier is has melt first the ice and now is removing sediment from the lateral morine uh but has also occurred in the past in these

Aror locations and will likely occur in the future in this location okay so I now move to this location the the Eastern uh morine uh you can see here an or photo was 1969 uh where you see the morine the lateral morine from the little ice age

And a rem remnant of the Dead ice that is located in the in the valley floor uh what I you I want you to focus on are these two Boulders here which you can see uh highlighted by the arrows uh which are standing on the um

Eastern side of the morine and that you can also see in the auto photos of 2021 located here and you see that the Western borders is now standing right at the Crest at the edge of the of the morine so uh we see that the morine is

Uh um backward so it’s been eroded backward it’s been moved backward and we can estimate the volume of sediment that has been eroded by this portion of the Marine only the portion that is above the dead ice and we calculated a volume of 30 to 40,000 cubic meter uh of

Sediment this value is in agreement with the volume calculated from the dod so the um differential DMS since 2005 which show a volume of 12,000 cubic meters so if we assume that erosion has occurred more or less constantly over time this yelds a rate of 750 cubic met per year I

Have to point out that this volume represent the volume of sediment eroded from the morine but not entrained to the flu system because of course if you see sorry if you see at the bottom of the morine here you see that most of the material has been deposited in this um

Teras that which is now vegetated so in this portion of the morine the material is not connected to the fluvial channel while in the upper part here it is uh connected and the material that is eroded from the upper part can go directly into the flugal

System so um now in this picture you see uh evolution of the erosion and deposition Through Time H with a different uh dhms that we have available for these time periods uh well it’s may be a bit confusing but what I want you to show is again this portion of the

Morine where you see a lot of erosion occurring in the upper part but also a lot of deposition in this bluish color that is occurring at the morine foot and similar thing that is uh happening in this portion of the merine where you can clearly recognize this fun shape

Morphology at the bottom of the morine so um even if the merine is producing sediment is uh it looks like this sediment is not being delivered to the flugal system so in the end what should we expect for the future in terms of siment

Yells well I now show you the um the the the profile of this channel reach here which you can see here uh well what is um visible in this in this uh picture is that you see in the lower section of the profile shows a convex shape which is

Supposed to be uh in equilibrium with the water and sediment discharge so when I river is in equilibrium we expect that it has this shape this convex shape but the upper part of the river shows a very straight profile meaning that is not in equilibrium yet with its uh water and

Sediment Supply and of course this is quite normal because the Upper Ridge has been only recently uh freed from Ice so it is normal that is not yet in equilibrium now if we look at the cross-section along this channel rid uh we see that most of the adjustments so

The upper reach a b see is uh adjusting through lateral erosion so now you see in black is a 2005 profile and in blue is 2021 so you see that most of the erosion occurs at the at the SL at the banks of the of the channel meaning that

The river is eroding the morine at the foot so um now if we want to uh see what should we expect for the future we know that will continue to supply sediment either in a constant rate or through sporadic events but we will have an increase in Channel Andor rain

Connectivity because of this lateral erosion and channel adjustment so at the end we should expect an increase in sediment in trained in the flu system if we want to have a visual visualization of this concept is that while glacial is retiring and channel channel is adjusting we can have secondary picks of

S and discharge which follow this glacial Retreat and um en Challen uh morphology adjustment and of course this adjustment can also Ur once the glacier is completely disappeared but then we will have to argue uh how the changes in water discharge can uh affect the morphology

Of the CH okay I hope have been clear and if you have any question please go ahead yeah hey everyone um so as Susan just said I will talk about global patterns and trends of glacial Lake Outburst floods but before I dive right into this topic I want to give you a quick

Definition of what a glacial Lake outb flood actually is and why we care about them so glacial Lake outb flood also called Glo is basically just a sudden release of water from a glacial Reservoir but there are actually different types of glacial reservoirs and I show you two of them here so IEM

Legs and random legs and the reason why I’m showing those two types is because I will talk predominantly about these in my short presentation and yeah so I leges here on the left are basically just uh water reservoirs damed at the Surface by the glacier body so for instance by uh in a

Side belly of a glacier whereas morum legs here on the right are legs that form after Glacier Retreats and this creates some space behind the Marine of the glacier and then the water can be trapped at this barrier um so as I said before there are multiple more leg types

But they all have something in common and that is that they can burst out and have quite catastrophic consequences uh for society but also for Geology so unfortunately um these flood often lead to the loss of life but also the resettlement of entire Villages then economic losses but also infrastructural

Damages for instant Hydro uh instance uh hydrop power plants which are quite important in uh many mountain regions at the moment and then of course we also have geomorphic and ecologic impacts because these floods sit on top of the flood regime uh usually with extremely high peak discharges and can cause heavy

Erosion and deposition and thereby can also have impacts on the downstream ecology for instance by causing the die out of uh the local fish populations and on top of that we all know that we are experiencing global warming at the moment and in most of the mountain

Region this leads to Glacier Retreat and there actually have been some studies that had a look at the effects on this Glacier Retreat on um glacial legs and a study by sugar at Al 2020 found that there actually is a global increase in glacial Lake volume by 48% in just the

Last three decades and we can also see that here on the right um that this is one Lake in Nepal and it’s actually extending towards the glacier body with which is retreating here on the side so we see that these Glacier Lakes globally increase in volume so the question we

Ask ourselves is are there any temporal changes in glove magnitude and to have a look at this we constructed a database out of literature and web sources and added some mapped Outburst area change to capture the most important information about location date Outburst characteristics and impact

And we also have an online version of this database so if anyone is interested please look at this uh website uh but now just let’s jump to the first results um which is a spatial distribution of those legs uh that actually um cause outbursts so here we

Have again the two L types I’ve mentioned ice damp legs in light blue and mine damp legs in Orange these little dots here are all of uh Outburst locations and these bigger bubbles are the regional is the regional percentage of each uh Lake type that causes outbursts in each region and these

Numbers here are the number of reported outbursts we captured in our database and the first thing we see is that actually the majority of report or the most um gloves were reported in northb North America uh but we all what we can also see in this graph is uh that in

Scandinavia in nor America um most of the gloves occur from icem Lakes whereas in high mountain Asia and the Andes we see mostly gloves from morine D Lakes so let’s actually have a look at the flood uh magnitudes so in this case flood volume so this is a graph of the

Flood volume in million cubic meters on a natural lock scale between 1900 and 2022 here we have or two leg type classes again and let’s first have a look at the mine damed legs and we see that these flood volumes actually show a comparably high variance when we compare

To the ice stum legs but what we also can see uh when we look at the trends which are actually here indicated with the lines um these are just linear regressions uh we see that they do not point in the same direction for each area uh however we see that there are

Quite large confidence intervals but what we take out of this is that we don’t see overarching trend for morine dent lakes and actually people already have been thinking about uh what can cause um the flood volumes of morine D Lakes to shift or what might be the difference between the study regions and

One uh point that came up is the Outburst mechanism so the way these floods are initiated which is also of course dependent on the conditions for instance of the Marine Dam or the surrounding of the lake but we don’t see that on a global um print

Yet so let’s continue with the ice St lakes and you can see first of all that the volumes of these floods are usually higher than the ones of morent lakes but but we also can see when we look at the trends is that in all of the study

Regions we see see rather a decrease in flat volume with time which is actually a bit surprising when we think about okay we saw an increase in glacial Lake volume on a global scale but when we think about it a little bit more that might be related to Glacier Mass loss

Because a lot of these Lakes drain uh by flotation so they float up the glacier body when a certain pressure is reached the water escapes and then these leges might drain again in the future and when the glacier dam is thinning because we see Glacier Mass loss uh that might

Limit the storing capacity because less pressure might be needed to lift up the glacier again so we wanted to have a look at this uh at different Iceland lakes around the world but I will just show you one example here which is Hidden Creek Lake in Alaska and what you

Can see in this graph is first of all the lake area between 2000 and 2019 and we see that the lake was progressively decreasing in size actually by 45% between those two years and what we can see too is that in the same time uh the glacier was thinning and uh so we

Thought it might be good to try to bring glacial thinning in relation to our reported flug magnitude petas which are flood volume and Peak distarch so these are actually the gression slopes of uh two different models between glacial thinning and flat volume and Peak discharge for different lakes around the

World you can see up here uh so positive values here would for instance mean continuing Glacier thinning uh would cause or and at the same time uh decreasing Peak discharges for this part of the graph whever we see that it’s not really consistent here so we see a lot

Of um disturbances um so we concluded that there is only a moderate correlation between the glacial thinning and the reported magnitudes we observed however um our what we took out of this is that it is course much more complex uh so for instance some Lakes drain through subglacial tunnels uh which are

Formed during their first Outburst then they refreeze in winter again and then also maybe less pressure might be needed to reopen that tunnels again but there might be further reasons we want to have a look at so to conclude this and sum this up uh so our data basically showed that

Gloves from Ice temp Lakes decreased in magnitude while morine D Lakes had high variability but when we look at future perspectives it’s quite clear that ice legs will become fewer they already do because they are bound to the existence of glaciers while morine temp ples increase in the number and size and to

Give you just a quick Outlook what we want plan to do in the future so we saw that these magnitudes are changing but we are not sure on a global pattern what does it mean for any geomorphic processes so that kind of relates to Sarah talk um will we see more or less

Sediment transport from these uh Outburst fls so yeah thanks for your attention so good afternoon my name is Simon K I’m a Dr R student at the University of Cs and I’d like to thank you for the opportunity to talk about the role of teroc cast processes in the

Initiation of Alpine Deb flows or de debris Flows In pammer Frost affected ter so this talk will first first introduce you to a sequence of events that hit an Alpine Valley in troll about 3 years ago and then go on identifying the most important mechanisms that were responsible for initiating this sequence of

Events so what happened on August 13 2019 a ocast lake that had developed on top of a rock glacia rapidly drained and initiated a massive de flow so the democast L which is indicated in blue in the photograph had started to develop several weeks earlier on top of an

Active rock glacier that is indicated by the yellow highlighted area in the photo an active rock gler is basically a slowly Downs slope creeping mixture of ice and debris and after several weeks of development this Lake drained within couple of hours basically within one day and initiated

This debr flow at the Rock leer front which is shown in red and uh thereby displaced about 50,000 cubic met of ciment that rapidly traveled down the steep slope below the rock leer front spread out across the valley axis blocked the main river running along the valley and impounded

The lake of about 120,000 cubic meters of water during the following days then there was an excavation channel thck to to prevent the potential the catastrophic Outburst now the interesting thing here is that it is not so clear what caused or what initiated this process

Chain and to get an idea about this we started um looking for potentially destabilizing factors that initiated this events analyzing them or first grouping them into these three groups predisposing factors that’s um that describe the static setting in which the landslide occurred then Preparatory factors that slowly shifted the slope in

A state made it susceptible to failure and triggering factors that actually caused the failure then and we started by evaluating each of these factors individually to identify the most important drivers for the flow initiation and then went on assessing critical combinations of these factors to reconstruct the D flow

Mechanism uh we did so with the overall aim of being able to assess the hazard potential of these active Rock glaciers because Rock Glaciers are really widespread phenomenon in Alpine Landscapes or permafrost effected landscape and therefore might be critical in this sense and the next couple of slides will now take you

Through the most important of these identified factors starting with the topographical setting so the debr flow initiated at the Rock ler front which is steep which means of course shear stress is are high sensitivity to liquifaction is High all the material that is eroded at the front

And there’s a lot of material eroded because the the slow movement of the rock leer down down downhill is approximately balanced by the erosion rate at the front and all these loose sediment is available for mobilization further down the slope it does it does not form a stabilizing cone at the toe

Of the front so this is obviously already a kind of meta stable situation and next interesting thing is if we have a look at the termal ground conditions at the Deb flow initiation Zone which is given by the black circle we see that it is at the lower boundary

Of pammer frost here which means that presumably there is some water content or high liquid water content in the PO space that a lot of sediment is already unfrozen and therefore lose and available for mobilization and if there is some ice present that it might already show quite High

Ility um it looks like there was actually some ice present if you have a look at the upper two of these photographs taking several days after the debris flow initiated especially at the upper right you can see this overhang which is formed by Frozen debris indicating that some ice was

Present at the time of De flow initiation here next we analyzed the grain size distribution of the rock ler front and the results are depicted here we found out that it is pretty poorly sorted basically consisted of sand and gravel and if if you compare it to typical Deb flow material

Indicated by the gray Dash lines here you see that the distribution seem to match kind of and this is important because this loose material is known to respond by in a contractive manner to sheer stress meaning that if the pore space is saturated with water then um

There is the possib or then High pore pressures are produc proded which are driving the de flow movement basically so we went on analyzing the climate in the Circ above the de flow initiation Zone and basically we compared the weeks and months preceding the de flow to earlier years to find out

Whether there is some significant differences uh we found out that while precipitation was pretty much around the long-term average in 2019 a temperature was really really high in the weeks preceding the flow which means that a lot of energy basically was available for melting of pammer frost ice in the

Weeks preceding the debris flow now if we’re having a look at potential triggering factors first we noted that there was a light rainfall event in the night directly preceding the debr flow um we conducted a frequency analysis comparing this rainfall event to all the rainfall events that had hit hit the Circuit of

The rock gler since 2012 which are indicated here by the gray dots the event before the de slide is indicated in the by the Red Dot and you see that this rainfall event was not especially severe neither in terms of intensity nor in terms of event

Duration so and if you compare it to the critical rainfall thresh for de flow initiation in tyal which is given by the black line it also plots below the line and then finally we compared it to several rainfall events that are known to have triggered debr flow with other

Active Rock leer fronts given by the black dots and we also found out that our rainfall event here was way lower so probably it was not the triggering factor however if we have a look at another potential triggering Factor the situation becomes much clearer and this is this thermocast Lake that had

Developed during the weeks before on the top of the rock ler and the red dotted line line gives the extent of this Lake one day before or immediately before the de flow and the photo was taken about one day later and as you can see the

Lake is almost empty it it had drained within this one day more or less there’s still some water left at the very bottom of the lake but this is just really minor amount compared to the total volume before and it’s drained through this newly formed crass which is massive

In the Rock lecia ice cor about 2 m High more than one meter wide and forms part of a newly developed Channel network you can see here the cup structures of this Channel network connecting the position of the former teroc Lake in the Southeast to the de flow initiation Zone in the

Northwest so summing up we have a couple of predisposing and Preparatory factors that are not good for stability here the front is steep it it’s about 30° which means High she stresses potential for liquefaction there’s a lot of paros degradation going on around the initiation Zone and which decreases the

Shear strength elevates the water content and makes sure that a lot of loose sediment is available which is also mature but a continued Rock movement and this sediment also shows a bad or a a grain cell distribution that makes it susceptible to debr flow initiation regarding the triggering

Factor it’s likely that the teroc lake Outburst above although it was 300 met behind the front was um the main triggering factor here because it was able to supply water at a rate of several cubic meters per second and developed very rapidly during this summer so what did we learn from

This we we see that rock gles really pose um multihazard elements in this alpen Landscapes because of their steep fronts the large amount of stat available having a instable or a susceptible Gres distribution and because of their changing internal structure and in this specific situation here we see that groundw flow was

Actually governing slope stability at the Rock ler front because of because of this rapidly developing Channel network that had the capability to transport large amounts of water within a short time along these channels and because the storage capability provided by this termal Lake On Top of the Rock leer and

The critical thing for risk assessment or hazard assessment is that the reorganization of these waterf flow paths within the rock laser happened on really really short time scales that were on the order of weeks which makes it really difficult to predict these kinds of events thank

You go thanks for the introduction um we move a bit up slope where the material comes from and if you think about Frost cracking you always think about okay a temperature regime that enhances weathering and there are a few scientists that try to pinpoint where this regime could look like or could be

And hel and colleagues there found out a regime between minus 6 and minus 3 degrees on a very low strength barer Sandstone Robert aners developed a model where he said the cracking window who he was the one who established the term lies between minus 8 and -3 degrees but

If you um use one of the most sophisticated models to model ice pressure and frost cing by Wen hel and apply it to Westerly granard you see that the frost cracking is between minus 20 and Min -2 and it depends a bit on the initial crack lengths so of rock

Properties and also the freezing duration so what my question is uh when do rocks crack in in uper environments and the second is if there’s some Frost cracking window um existing cannot see it in the landscape cannot see it on the mountain is there like an elevation range where these temperature conditions

Are um are there and is the elevation range like a hot spot of erosion and can I um yeah prove this by data so hypthesis one is is Frost cracking and alpan rocks temperature dependent and hypothesis two is this Frost cracking a main driver of the crumbling so of the

Rockfall to address hypthesis one we took uh some rock samples from a quarry that made up the main uh yeah one of the major theologies in the north calcerous alss which is fetan limestone and we put this uh Rock onto a water reservoir above a heater and we

Insulated all the sides and freeze The Rock from top to bottom and we got the temperature measurements or sensors um in different depth of this rock and also acoustic emission sensors at the top and at the side and we use acoustic emission as a proxy for

Cracking the next step is what kind of thermal regime we want to apply and these are all teral regimes from measurement stations or Rock temperature loggers above 3,000 mters or around 3,000 mters and you see what they all have in common at some point of time

They’re below 0 degrees so they have fre in conditions some are fluctuating much more than others like the matorn compared to the hung Valley which is due to less snow cover at the M horn and more snow cover at the hung Valley we applied a a temperature regime

Where we which is more comparable to the hungy Valley so we cool down our Rock keep the temperature constant at yeah a steady temperature range increase it and a time again another steady temperature range in increase it so it’s bit like step like the reason why we do this is

We try to exclude other factors than ice so we don’t want to produce Thal stresses because then we can’t conclude if theum acoustic emission numbers that we collect are really are connected to ice or to Thermal stresses the other thing that we need is a thermal gradient so we have cold

Conditions at the top and warm conditions at the bottom so we have positive temperatures that’s important due to the heater and the water reservoir provides water that can move upwards and enable ICE segregation so we have an open system where water can move and can um yeah form ice lenses or grow ice

Lenses our data you see we have temperature plotted against time and we reduce this temperature until one uh until after um phase one then we increase it slightly to phase two increase it again and so on and every door you see is a an acoustic emission

Event and the yellow ones are in during the transition when we cool or warm The Rock and the orange one is during the um steady phases and what we see is we’ve observe a lot of um acoustic emission when events during initial Cooling and then you see that the number of acoustic

Emission events decreases the warmer the um cooling phas is this slide shows um the cumulative number of acoustic emission events and you see that you have the largest increase and 95% of the events is during the initial Cooling and during the first phases we now try to find out okay

What’s causes these events we modeled Thal stress that we try to exclude by our setup but you see we have some stress when we change temperature so at the beginning or between the phases so there we can’t say if it’s ice pulled up or if it’s a Thal stress at causing this crack

Then we modeled uh the ice pressure which is in Orange in 4 cm depth and in 15 cm St and as soon as we froze the rock the ice pressure built up and if it cross a critical threshold which is Rock strengths dependent the cracks in the

Rock will grow and you see that the major growth starts at the beginning in Phase One and phase two and then we have no further um growth which is due to the ice pressure that this decreases because it’s um your temperature dependent and you see that this um the graph is very

Similar to the acoustic emission graph that we observed so this is like our yeah Smoking Gun that we think that ice pressure is the major contributor of These acoustic emissions if we now try to classify this acoustic emission events um into temperature regimes just like a palad

And colleagues we observed that the most uh cracking occurred during phase one and two and this is the majority and only very minor cracking betweenus 6 and minus1 so what we see or what we observe is the shift of the maybe traditional Frost cracking window and this is in our

Case because Vin Limestone has a much harder strength than barer Sandstone but B Sanson is a a best sedimentary rock that will not make up Alpine cliffs come to the second part of the talk if there is a frost kicking window can we see it in our landscape and for this

Purpose we went into the hung Valley and what you see is a North facing rock wall the matorn would be somewhere over there we’re in southern Switzerland we have a small Glazier and The Rock worlds they are ranging from 2,500 met up to 3,300 M and theology is ranging from low

Strengths a shis quad slate to high tensal strengths amp fibid so we have a variety of ly and what we used was or what we collect first was Rock temperature so we have five locations where we collect Rock temperature and record it for 3 years and what you see is that The Rock

Temperature decreases the higher I go so you have more freezing at higher locations and you see also that this rock temperature is highly affected by snow cover which increases also the duration with increasing elevation and we use this rock temperature to run a frost tracking model that incorporates

Strengths which is a model by rample and colleagues and what you can see over here is the first that the magnitude of frost cracking is different depending on the ly So You observe a higher Frost cracking rate if The Rock has a low strength and lower if it has a high

Strength and the um the plot shows um Frost work against elevation you see that it increases until we reach an elevation between 2,900 and 3,000 M and then it decreases again and what we now suggest that we would observe more rockfall in this area and you see this

Are Rock full volumes derived from terrestrial laser scanning for like three years and every you circle is um an event and the circle size refers to the event volume and you see that yeah we can see a clustering over there however the scan rock wall area differs

A bit so we try to normalize the rockfall volume by the area and buy time to get a rock ball U erosion rate and if we calculate this you see that The Rock ball erosion rate increases with elevation and you find that the yeah highest rate is also in

The area where we’ve observed the highest Frost cracking it stays high and then it decreases so it fits quite well not perfect however you see okay we have also other factors that can play a role like a glazier that has a certain size but was

Not always as big as in the picture so maybe bigger in the past and what we do we reconstructed the Glazier size and then we normalize the rockfall by the area delocated in a certain period so we have 28 years 72 years and so on and we

Um plot erosion rate against again and you see that the highest rate are are achieved in the same elevation range because it’s recently deglaciated also pamr can play a role and we model pamus distribution and 95% of all these rockfalls were located in pfost terrain and we normalized that the

Rockfall volume by the area with a certain pmer Frost temperature so is mean an rock surface temperature and you see also if if you plot this against elevation you have an increase of the erosion rate and the highest PS are around between 2,900 and like 3,200 M so

To sum it up you have maybe a connection between Frost cracking and erosion rate but also other paraglacial processes or parag glal processes can play a role and usually have an Mountain environment where you have high Frost tracking but in it’s also an environment affected by a Glazer Retreat and permafrost

Th to answer our um hypothesis so one Frost cracking in Alan rocks is temperature dependent I would say yes but the temperature range is strength dependent and seldom between minus 8 andus 3 degrees so if you want to model it you need to include lithology hypothesis 2 is frustrating a

Main driver of crumbling of rockfall I would say maybe Frost cracking is one driver but you have other drivers as well and and there is no smoking gun that shows okay PR cring is a major controlling Factor so if you want to model um erosion rate you should include

Other processes as well yeah thank you for your attention and looking forward for your questions which there are probably in the chat uh so yeah I’m aland Pini PhD student at eth surik and a research assistant at sub University of applied sciences and arts of sou Switzerland um today I present a study

Part of my PhD in which investigate the role of the delation on the Rock Lop stability hereby described the new insights of the chronology of the large Roop collapses in the southern s results the investigation of the slope deformation subsequent the deglaciation is of current interest as we are observing an increasingly rapid

Glacial retreat at global scale and consequent exposure of slopes that may fail and generate collapses which may endanger local communities so the question that arises is can the study of the slope deformation in former paraglacial environments help to know the behavior of the deglaciated slopes in the next centuries for uh assessing the

Connection between glacia Retreat and the occurrence of slope collapses uh detailed geochronological assessment of both phenomena is essential the souter results meant here as the northern part valleys of the Canton Chino and Adent valleys of the Canton of graund are an interesting region to study this correlation because um the

Phases of the glacial Retreat after the last glacial maximum are well known thanks the numerous radiocarbon data of organic matter and cosmogenic nucleid of eratic Boulders and several deposits of rock slop collapses have never been dated with the exception of the konico landslide known to be one of the largest crystalling rock

Avalanche in the Alps So In This research U This research HS to define the age of exposure of deposits of rock slope collapses and relate the results to the deglaciation to obtain a morphodynamic interpretation um now a quick view on how the Southerns could appear during the last glacial

Maximum uh the ballet floors were covered by more than 1,000 MERS of ice that left only the Peaks emerging as n attacks the region after the last glacial maximum was characterized by four main interstadial intercut by stadials of U non extent and a rapid GLA regression has been identified between the kunas and

Basa stadials where in less than 600 years the glacier had regressed of about 30 kilometers Upstream nowadays the region shows a large number of rock slop collapses with volumes of even millions of cubic meters uh given the cosic number of deposits to be dated we choose an inexpensive and Rapid method theid

Hammer already used in this dire to reconstruct the dynamic evolution of rock glazers um the method consist to attribute to each rock slide deposit a strength value and relating it to an exposure age the strength value is obtained through the use of the shmmer which consist of a cylinder with an

Internal spring that loads a tip the tip is thrown against The Rock and the instrument gives a rebound value that is inversely proportional to the state of rock alteration so uh the age of exposure of the Rock the requirements to apply the method are a common morphoclimatic

Context uh common lithology and at least two deposits of nonexposure Ages uh the exposure age can be obtained by a regression line correlating exposure age and the rebound value in green you can see the exposure age of the deposit of rock slope collapses and in blow the exposure ages by cosmogenic nucle

Dating uh we studied the deposits of seven rockos slop collapses with variation of block sides and block number for deposits with um large blocks we obtained more impacts per block with small blocks we tested a larger number of those with with less impacts per block but in both cases we we made about

500 impacts per block um the regression line is then outlined by lineal regression between berum 10 exposure age of the konic or Avalanche deposit and the berum 10 ex explos um exposure age of erati blocks uh these constraints are optimal because the lithology of the deposits is similar

And the age difference is of thousand of years and in addition we tested a query block recently broke broken which uh gave a minan air value of 63 and the 1513 Monon AO cavage deposit which gave a air value of 58 and and these data are a further

Evidence of the relationship between uh exposure time and air value um here we compare the AG obtained with Schmid Hammer dating and the age of deglaciation per site it is possible to observe three clusters of age of collapses and the rock calanche of chent IO and noran took place immediately

During the delation and they represent an early paragan response and The Rock slope collapses of Bodo in Tio Canton bodoo and konico uh represent a few Millennia delayed response to the deglaciation and if we consider also three Rock slope deformation fell in historical times Monte Soros prono or not yet collapsed it is

Possible to observe a third cluster with a very long delay more than 14 Millennia after the delation uh flanking the graph of the sedimentation rate of the aluvial flu plane of the Tio River delta we find here above and the graph that puts in relation the age of collapse and the

Volumes of the deposits we can make some observations uh it seems not to be a direct correlation between volume of the deposits and time after delation and DEP abondance of rock slope collapses following the deglaciation is in accordance with the sedimentation rate of the aluvial flu plane the possible absence of large

Collapses during the the OS in termal maximum until until historic times and uh an increase in the Rock slope collapses during the last Millennium so um for what I shown I can draw the following conclusions um we observe relation between the age of rock slop collapses and the sedimentation rate has both

Follow the paraglacial erosion model in our data there is no direct relation between the volume and the age of rock slope collapses the same can be said for the relation between the age of the collapses and the time of the slope exposure after the deglaciation but remains some open

Questions one is about the relation between the I thickness above the slope and the subsequent Rock slope failure and a further question could be about the investigation of a relation between the deglaciation rate and the age of the slop collapses so uh thank you for your attention if you you have

Questions thank you so much okay um good afternoon everyone as you may know landslides are among one of the most significant natural hazards across the globe responsible for up to thousands of fatalities every year worldwide and even if most of these fatalities occur H during High Velocity landslides L slow

Moving landslides are are a significant source of concern for local populations as they continuously impact important infrastructure such as agricultural assets houses and roads for this reason it is important to study them but also because studing slow moving landslides can actually lead us to a better understanding of the physical processes

That cover ER both slow and Rapid landslides and that’s why today I will be talking about the potential of long-term monitoring of slow moving landslides ESP specifically in low Austria I’m Alejandra I’m a PhD student from the University of vien so I’m going to give you a brief introduction of the

Slow moving landslides these are a processes that creeps at rates of millimeters uh from millimeters to meters per year they are normally occurring at mechanically weak uh Rich clay content soils and they’re characterized also by a complex subsurface eological system that contributes to this um to non-uniform spatial and temporal kinematic behavior

Of these processes the reev the relevance of a slow moving Landslide studies is because based on different examples through literature and through of course examples that have occurred in the past it demonstrate it was demonstrated that actually uh slow moving LLS can transition into fast H moving processes

And also cascading hazards can actually occur within this H land like bodies therefore um slow moving landslides can actually be identified as early deformation signals before llight with catastrophic effects occur and even though this is already demonstrated through different case studies um there is there slow moving landslides are

Constantly overlooked due to the high amount of time and resources that are necessary to study them in the case of of lower Austria this is a region that is characterized also by a high complex geology the this is a region that corresponds to a complex transition zone between a different units specifically

The fles Zone the clip and Zone and calcarius units H The cpen Zone and the FES zone are geology geological units characterized by a High um heterogenity and high contents of clay that makes it makes them very susceptible to the occurrence of landslides these processes along uh some socioeconomic uh developments proper of

The region such as Agricultural Development road construction urbanization and make the region um very in high risk to uh the impacts of these processes therefore it is important to study What could be the potential impacts of these processes in the in this region however there’s still a lack of understanding of the H

Frequency intensity relationships and triggering mechanism mechanism of the of these processes in the area and therefore that’s why my the research group I’m part of theage group ER carried out a long-term monitoring project called the nolik project to investigate landslides in lower ostra since 2015 this was with the objective of

Understanding the controlling and triggering factors of landslides to estimate the potential risk for population and infrastructure and to implement new methods for Landslide analysis all of that with the main goal of contribut to the resilience of local communities through the co-development and implementation of disaster R reduction measures such as a potential

Implementation of our early warning system in the area and that’s why we have three study sites in three different uh landslides in lower Austria we have the Hofer M study site s study site and the branch study site in each site we have implemented carried out different uh surface and subsurface

Methods such as the rest laser scanning surveying UAV surveying GE morphological mapping Dynamic probing percussion drilling but also we have installed on the field a meteorological station Pomers inclinometers and TDR sensors today because of the amount of time I’m we just going to show you some results from our most recent study side

This is the branch. landslide this is a complex deep seated Landslide was depth is assumed to be at 20 M depth H from um calculated from the estimated from the different geop physical analysis in the past H in the last year we were able to install H five inclinometers three

Pomers and DDR sensors and a meteorological station there in addition to that we were we did some Dynamic proving um a percussion drilling to have a better understanding of the sliding material So based on the integration and Analysis of the data we came up uh we were able to identify three main things

First based on the observation of the digital elevation model and on the UAB data it was possible to detect different geomorphological features that indicate us different patterns of movement so we were able to identify uh different like several active areas that have a be a different distribution from the general landslide

That was um then we were were able to compare those observations those superficial observations with subsurface information from the inclinometer data and then we were able to see through the inclinometer graphs that you can see here which represent the cumulative displacement in depth then it was possible to observe that actually the

The clinometers are the the slope is moving at different rates in different parts so you can in in clinometer a h the cumulative displacement is 10 cm in 7 months the clinometer B has shown a displacement of 1 cimer in seven months while the clinometer C and deep have

Shown only less than half cimeter in the same period of time so this actually confirms us the nonuniform spal distribution of these processes and also the indication of that there are different shall processes occurring within the Deep seated Landslide body also um considering the most active h part of

The landslide body that corresponds to the active area close to inclinometer a we were able to take a closer look and we were able to confirm that there is not only a spatial non-uniformity but a temporal non-uniformity when you have uh different periods of activity we you have several moments where the process

Dis accelerates and some others when it accelerates and this could be potentially linked to changes in ground water level and for consequently changes import water pressures mainly explained by precipitation and snow melting processes so in general terms long-term monitoring is an useful tool that provide us important information for

Land slide analysis we were able to confirm this non-uniform spal and temporal Landslide behavior of these slow processes also that branch that Landslide the reason stud side correspond to a complex landl in which uh we have shallower processes within the Deep seated Landslide body however it is still necessary to improve our

Understanding of the forcing and mechanisms of these processes to define the critical combinations that could give us idea of what could trigger accelerations in this area and therefore to estimate the potential impact of those Hazard scenarios so as perspectives what we want what is the

Next step the next step is to use the information to integrate it into a better conceptual models that could be used for numerical modeling to actually be able to simulate these nonuniform H changes that could give us information of potential Hazard scenarios and therefore the we could use

To estimate the potential impact of those scenarios also another perspective is to be able to integrate H into those models the anthropogenic influence this is something that we would like to do in the future and also another perspective to is to use artificial intelligence to be able to identify the critical combinations and

What could actually cause acceleration of these slow moving processes in our study sites thank you very much thanks um stop me if you can see my screen or can me so thanks for the opportunity to present work here um I will start with a question about could

Um very large and very old can be thousands of years old Landslide be destabilized by urbanization and who it could and in this case it’s particularly about informal urbanization so what I’m going to show you here is kind of analysis of how a very large landslides uh behaves over time and how this

Behavior changed alongside um its urbanization over 70 year time period um it’s great I can be very quick about explaining what slow moving Landslide are um those are typically deep seats so it can be 100 of meter deep they can be square kilometer in size they’re quite big part of the heat

Slope which moves um and what’s quite nice about them is when you analyze the Dynamics of the landslide so its velocity and change of velocity over time you can understand quite well about the mechanism of the land slide so who in slopes behaves and what controls the

Motion and the mechanism of those land slides another part which is I believe quite important here is um we are working in the tropics um and it’s quite important because it’s a very Landslide PR U it’s typically Landslide prone areas uh well being quite overlooked in the literature uh

Landslide prone because of two main aspects natural natural environment um we have typically High total precipitation high intensity precipitation we have high temperature over the entire year so it’s meaning we have weathering of the Rocks which is quite deep um so alteration of the Rocks reduce the

Sheer strength of the rocks and make slopes more Landslide gr alongside that you have quite major um demographic um and economic change which are sweeping ac across tropical Landscapes so you will have um Rebrand expansion agricultural expansions which will change um the land corver which may also induce the occurrence of more Landslide

So you have what we call call The High um natural landslide susceptibility in many places of the tropics and alongside that you also have quite High population density and high social vulnerability so you have a lot of people living in an area where you have a lot of chins to

Have land slight so a lot of um OD spots of population exposure to land slide are located in the tropics alongside those all those points um I pick the same same figure as the previous talk from quite nice which analyzed our understanding of slow moving land slides and here showed um

Some of the key side from which your understanding the mechanism of landslide comes from and you directly situate where I want to go most of them are located in high income High latitude countries so most of understanding comes from for instance landslide in the Alps where environmental conditions are quite

Different from what you can have for instance in central Africa so here we are working uh we’ll be working in St Africa in eastern the Democratic Republic of the Congo at the border with Randa we are South ofu in the city of bukavu um it’s a 1 million inhabitant

City um so quite densely inhabited in a landslide prone area and you have today about one3 of the city which is built on landslides so not all are active um all Landslide are here that in in red and one is part active it’s outline in yellow this is the land slide that we

Called Fu and this will be um the one we will be focusing on today so this is f Landslide um you seeu you have this Landslide is probably thousand of years old it’s clearly precedes um human installation in the area um but today you have about 880,000 people that lives on this active

Landslides it’s quite large one .5 square kilometer 90 M depth um and um what we will do here is focus at two different scale looking at um short time scale quite with high tempal resolution analyze all the motion dynamics of the land slide today oh it is thanks to um

Satellite imagery but also look um over change over time so whole dynamic of the L slide evolved alongside its urbanization so let’s F let’s first have a look at Short T controls um for that we use sry um we are the tropics so it’s first you have persistance cloud cover

So it’s difficult to rely on optical satellite image but you also have um it’s in two measurement are quite complex to obtain it’s difficult to maintain instrument and install them in Thea so we could rely on sry it work perfectly uh what we did is to combine

Um two sensor Cosmos skate and Sentinel one which is quite nice because we could um quite increase quite a lot our temporal samping so we have one image every two day what you have here are three figures showing deformation uh over the city of bavo with on the left the eastwest

Displacement component in the middle vertical displacement component and on the right the north south uh displacement component you directly see you have one hot spot of deformation and that’s the fun Landslide inside it you see you have different spots where you have higher deformation pattern I won’t

Go into detail here but that’s also quite interesting to see um to analyze the mechanism of the lens slight and how it changed what I will show you is um time Ser of displacements over time that we will compare to PO water pressure so you have displacements in Orange so

Vertical 2D actually here displacement of the landslide an average over the land slide and in blue you have so po pressure po pressure here simulat what it is it is a way to um show the temporal um Gap in between the moment you have rain on the landslide and the

Time it it takes to infiltrate within the slope and so when it will actually change the slope stress State um this here is simply simulated we have no data on the ground um what you see is that we have um so we can of course compare to rainfall from which the poor water

Pressure comes but also earthquake URS what we see is that it’s mostly rainfall and so the B water pressure that um controls the overall motion of the landslide to time we have lowest velocity during the triy season um highest velocity with the onset of the r season Etc this was quite expected what

Was not is that this very large landslides very deep responds very rapidly to um rainfall for instance at the end of the dry seasons it will in a matter of a few day with the first rains you will have an acceleration of the landslide that we can catch here with

The insert this was quite unexpected so you have quite small difference in slope effective stress which can drive change in the landslide motion so now we know that small change in effective stress can change the land slide motion um did it behaved alongside drastic change um that comes with

Urbanization you have here a picture more less the same place over fun Landslide on the left in 1959 and on the right 2018 you directly see that a lot Chang on the slope so we’ll investigate that now um here is historical Arial image from 1947 and we will go forward

In time what you can see is the evolution for instance of the urban fabric of the landslides here only the two of the landslide is urbanized but if you go forther in time for instance here in 1959 you see that U people start to settle more UPS slope and it continues

Over time this is 1979 74 sorry this is 2001 now the entire Landslide is urbanized and when you go further in time what you see is that you have an increase in the density of um Urban fabric within the land slide what we did is to plots and

Measure the evolution of the urban fabric over time and plot that alongside the velocity of the landslide and for that we discriminate between two different Zone within the landslide I won’t go too much into detail but what you see that we have one unit that’s moveed faster and this is unit this unit

Was urbanized later than the other so we have um know here the evolution of the urban fabric over the landslide and the surface velocity the unit that was urbanized latest it was urbanized in the ’90s it’s upper in the slope this was alongside um dramatic um you had some

Conflict in the area you have a lot of migration to the city to seek security and alongside those migration you had um a very drastic increase in the population density or de area which led to here at the same time an increase in the velocity of the landslide so why is that

Um is it because of the weight of the building or something else what we uh long story short here what we see is that we had a change in the surface or the water infiltrate and drain in the water in the slopes alongside urbanization think of building of drains

Of Roads um Etc and you had convergence of the drainage over that area which now move the fastest which see a difference uh which before was moving alongside the entire Landslide same base and now was moving F much faster um and so what we see is that it’s a

Kind of feedback loop you have convergence of drainage so you have um higher velocity or more infiltration of death zone so you will have higher velocity so you have for instance damage to the drain drainage which will further increase the velocity of the that area and so we have this C self- reinforcing

Feedbacks between urbanization and um the land slide motion and so here what we show is that we have an influence of the urbanization on the landslide Dynamics to finish uh with some perspective um I have here some plots which show the evolution of uh the population which in which what what is

Parly striking is the evolution of urban population though more than half of the population lives in urban areas and this is particularly true for Africa and Asia where most of uh the future evolution is expected to be and these countries uh you will have for most of area you will

Have those tropical environmental condition that we describe here and why where I show where we show that we we can have some uh feedbacks in between urbanization even in formal urbanization and the Dynamics of very large old and deep seated Landslide that’s it