Multi-Technique Analysis and Landscape Evolution: Implications for Landslide-Fluvial Cascading Hazards Assessment

Guinau, Marta; Fernández-Jiménez, C.; Barra, Anna; Viaplana-Muzas, M.; Flores, Ariadna; Ortuño, María; Gonzalez, Marta; Pinyol, Jordi; Abancó, Clàudia

doi:10.5194/egusphere-egu24-14955

Abstract

The interaction between slope instability processes and river dynamics often triggers a cascade effect. Sediment influx from slopes can obstruct rivers, leading to upstream flooding and potential catastrophic flash floods downstream upon dam breakage. In addition, the incision of the drainage network steepens the valley hillslopes, further exacerbating slope instability processes, modifying the geomorphology and the sedimentary fluxes and increasing the occurrence of landslide-derived hazards. In this regard, a comprehensive and updated landslide inventory, especially focusing on the interconnection between landslides and drainage networks, is crucial for effective hazard assessment considering these cascading effects induced by slope and fluvial processes. This study presents advancements in landslide mapping by integrating data from Multi-Temporal Synthetic Aperture Radar (MT-InSAR) and landscape evolution analysis through geomorphological indices such as Chi, Normalized Channel Steepness Index (Ksn) and Stream Length-Gradient Index (SL). Identification of anomalies along rivers using Ksn and SL (knickpoints or knickzones) aided in pinpointing abnormal slopes due to sediment influx from landslides. Additionally, active areas were delineated using the ADAfinder tool, extracting data from MT-InSAR provided by the European Ground Motion Service (EGMS). This multi-technique analysis highlighted the slopes of interest. Landslides identified with these techniques were delimited and characterized in terms of type assignment, using 2x2 m DTM hillshades derived from airborne LiDAR data and field observations. The upper catchments of the Garona and Noguera Pallaresa rivers (central Pyrenees-NE Spain) were selected as study cases. The study highlights the disequilibrium in the watershed divide between Noguera Pallaresa and Garona basins, suggesting a transition toward equilibrium favouring a main divide migration towards the Noguera Pallaresa due to hillslope processes. The assessment of the equilibrium profile geometry of the Noguera Pallaresa river at a regional scale suggests at least two main knickpoints. The river sections downstream of the knickpoints are associated with landslides triggered by post-glacial dynamics and incision wave effects. Combining SL and Ksn curves with Active Deformation Areas (ADA) underscores areas with potentially reactivating deep-seated landslides, signifying potential high damages in case of low-probability but catastrophic reactivations. In conclusion, the integration of diverse methodologies shed light on the spatial relationship between transient features in the landscape (knickpoints) and landslide occurrence, emphasizing the need for a comprehensive approach to mitigate landslide and fluvial risks in the Noguera Pallaresa and Garona river basins.

Multi-Technique Analysis and Landscape Evolution: Implications for Landslide-Fluvial Cascading Hazards Assessment

Author: Guinau, Marta,Fernández-Jiménez, C.,Barra, Anna,Viaplana-Muzas, M.,Flores, Ariadna,Ortuño, María,Gonzalez, Marta,Pinyol, Jordi,Abancó, Clàudia

Publisher: European Geosciences Union

Year: 2024

DOI: 10.5194/egusphere-egu24-14955

Source: https://digital.csic.es/bitstream/10261/356949/1/996456.pdf

EGU24-14955, upda ed on 02 May 2024
h ps://doi.o g/10.5194/egusphe e-egu24-14955
EGU Gene al Assembly 2024
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he C ea i e Commons A ibu ion 4.0 License.
Mul i-Technique Analysis and Landscape E olu ion: Implica ions o
Landslide-Flu ial Cascading Haza ds Assessmen
Ma a Guinau1, Celes e Fe nández-Jiménez1, Anna Ba a2, Ma c Viaplana-Muzas3, A iadna Flo es1,
Ma ia O uño1, Ma a González4, Jo di Pinyol4, and Clàudia Abancó5
1Depa men o Ea h and Ocean Dynamics, GRC RISKNAT, UB-Geomodels, Facul y o Ea h Sciences, Uni e si a de
Ba celona (UB), 08028 Ba celona, Spain ([email p o ec ed])
2Cen e Tecnològic de Telecomunicacions de Ca alunya (CTTC/CERCA), Geoma ics Di ision, 08860 Cas ellde els, Spain
([email p o ec ed])
3G oup o Dynamics o he Li hosphe e (GDL), Geosciences Ba celona, Geo3Bcn - CSIC, Ba celona, Spain
([email p o ec ed])
4Uni o ac i e geological p ocesses and Geological Haza d In o ma ion Sys em (SIRG). Ca og aphic and Geological Ins i u e
o Ca alonia, Pa c de Mon juïc S/N, 08038, Ba celona, Spain ([email p o ec ed])
5Depa men o Mine alogy, Pe ology and Applied Geology, Facul y o Ea h Sciences, Uni e si y o Ba celona, Ba celona,
Spain ([email p o ec ed])
The in e ac ion be ween slope ins abili y p ocesses and i e dynamics o en igge s a cascade
e ec . Sedimen in lux om slopes can obs uc i e s, leading o ups eam looding and po en ial
ca as ophic lash loods downs eam upon dam b eakage. In addi ion, he incision o he
d ainage ne wo k s eepens he alley hillslopes, u he exace ba ing slope ins abili y p ocesses,
modi ying he geomo phology and he sedimen a y luxes and inc easing he occu ence o
landslide-de i ed haza ds.
In his ega d, a comp ehensi e and upda ed landslide in en o y, especially ocusing on he
in e connec ion be ween landslides and d ainage ne wo ks, is c ucial o e ec i e haza d
assessmen conside ing hese cascading e ec s induced by slope and lu ial p ocesses.
This s udy p esen s ad ancemen s in landslide mapping by in eg a ing da a om Mul i-Tempo al
Syn he ic Ape u e Rada (MT-InSAR) and landscape e olu ion analysis h ough geomo phological
indices such as Chi, No malized Channel S eepness Index (Ksn) and S eam Leng h-G adien Index
(SL). Iden i ica ion o anomalies along i e s using Ksn and SL (knickpoin s o knickzones) aided in
pinpoin ing abno mal slopes due o sedimen in lux om landslides. Addi ionally, ac i e a eas
we e delinea ed using he ADA inde ool, ex ac ing da a om MT-InSAR p o ided by he
Eu opean G ound Mo ion Se ice (EGMS). This mul i- echnique analysis highligh ed he slopes o
in e es . Landslides iden i ied wi h hese echniques we e delimi ed and cha ac e ized in e ms o
ype assignmen , using 2x2 m DTM hillshades de i ed om ai bo ne LiDAR da a and ield
obse a ions.
The uppe ca chmen s o he Ga ona and Nogue a Palla esa i e s (cen al Py enees-NE Spain)
we e selec ed as s udy cases. The s udy highligh s he disequilib ium in he wa e shed di ide
be ween Nogue a Palla esa and Ga ona basins, sugges ing a ansi ion owa d equilib ium
a ou ing a main di ide mig a ion owa ds he Nogue a Palla esa due o hillslope p ocesses. The
assessmen o he equilib ium p o ile geome y o he Nogue a Palla esa i e a a egional scale
sugges s a leas wo main knickpoin s. The i e sec ions downs eam o he knickpoin s a e
associa ed wi h landslides igge ed by pos -glacial dynamics and incision wa e e ec s. Combining
SL and Ksn cu es wi h Ac i e De o ma ion A eas (ADA) unde sco es a eas wi h po en ially
eac i a ing deep-sea ed landslides, signi ying po en ial high damages in case o low-p obabili y
bu ca as ophic eac i a ions.
In conclusion, he in eg a ion o di e se me hodologies shed ligh on he spa ial ela ionship
be ween ansien ea u es in he landscape (knickpoin s) and landslide occu ence, emphasizing
he need o a comp ehensi e app oach o mi iga e landslide and lu ial isks in he Nogue a
Palla esa and Ga ona i e basins.
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