class: center, middle, inverse, title-slide # Road Construction and Rainfall as Landslide Triggers in the Rio Lucma Catchment, Eastern Cordillera Blanca, Peru ## vEGU21 | Session: GM4.13 ###
Lorena Abad
1
, Daniel Hölbling
1
, Adam Emmer
2
1
Department of Geoinformatics - Z_GIS, University of Salzburg, 5020 Salzburg, Austria
2
Institute of Geography and Regional Science, University of Graz, 8010 Graz, Austria
### Apr. 29, 2021 - 15:30 --- <div class="my-footer"><span> <a href="http://creativecommons.org/licenses/by/4.0/"><img src="https://i.creativecommons.org/l/by/4.0/88x31.png"height="25px"/></a>                             </span></div> ### Study Area .pull-left-35[ #### Rio Lucma Catchment - **Location**: eastern side of the Cordillera Blanca, Peru. - **Average rainfall** in the area: 1,169 mm/year, (80% during the rainy season, i.e. November to April). - **Elevation**: 2,500 - 5,830 m a.s.l. - **47 km** of unpaved roads were *recently* constructed to connect remote settlements. - Located in a high relief landslide-prone area. - Roads are rarely equipped with drainage or landslide mitigation measures. ] .pull-right-65[
] --- <div class="my-footer"><span> <a href="http://creativecommons.org/licenses/by/4.0/"><img src="https://i.creativecommons.org/l/by/4.0/88x31.png"height="25px"/></a>                             </span></div> ### Landslides along the recently constructed roads - Several landslides were triggered due to road construction, which affected an approximate area of 32 ha. - We identified and characterised these landslides by combining field mapping, visual interpretation and semi-automated analysis of satellite imagery (PlanetScope and RapidEye-2). <img src="figs/lucma_landslides_aoi_nosubset.png" width="100%" /> --- <div class="my-footer"><span> <a href="http://creativecommons.org/licenses/by/4.0/"><img src="https://i.creativecommons.org/l/by/4.0/88x31.png"height="25px"/></a>                             </span></div> ### Landslide characteristics for three subset areas - We investigated in detail three specific subsets, where we identified, delineated, and described **56 landslides**. - We derived quantitative (e.g., area, elevation of the headscarp and deposition, reach) and qualitative characteristics from these landslides, including their timing of concurrence with respect to road construction. <img src="figs/lucma_landslides_aoi.png" width="100%" /> --- <div class="my-footer"><span> <a href="http://creativecommons.org/licenses/by/4.0/"><img src="https://i.creativecommons.org/l/by/4.0/88x31.png"height="25px"/></a>                             </span></div> ### Landslide quantitative characteristics .panelset[ .panel[.panel-name[Results] <center><img src="figs/lucma_landslides_quant.png" height="300px" /></center> ] .panel[.panel-name[Descriptions] ![](figs/lucma_landslides_quant_desc.png) ] ] --- <div class="my-footer"><span> <a href="http://creativecommons.org/licenses/by/4.0/"><img src="https://i.creativecommons.org/l/by/4.0/88x31.png"height="25px"/></a>                             </span></div> ### Landslide qualitative characteristics .panelset[ .panel[.panel-name[Results] ![](figs/lucma_landslides_movement_type.png) <center><img src="figs/lucma_landslides_bars.png" height="210px" /></center> ] .panel[.panel-name[Categorization with respect to position to the road] .pull-left[ ![](figs/slope_evolution.png) ] .pull-right[ Schematic types of movements distinguished in this study. **(A)** Initial state before the construction of the road **(B)** Initial state after the construction of the road **(C)** Pre-failure conditions **(D)** Post-failure states **(1)** Landslides onto the road **(2)** Landslides downslope the road **(3)** Complex landslides ] ] ] --- <div class="my-footer"><span> <a href="http://creativecommons.org/licenses/by/4.0/"><img src="https://i.creativecommons.org/l/by/4.0/88x31.png"height="25px"/></a>                             </span></div> ### Landslide occurrence .panelset[ .panel[.panel-name[Visual interpretation] .pull-left[ ![](figs/lucma3.gif) ] .pull-right[ - We conducted a visual interpretation of satellite imagery on the [Planet Explorer online platform](https://www.planet.com/explorer/) to determine landslide occurrence and road construction dates. - Hence, the landslide occurrence and road construction dates refer to the first time the landslide or the new road, respectively, was observed on the satellute imagery. - Based on this interpretation we derived the timing of occurrence of the landslides as the number of days between road construction and landslide occurrence. ] ] .panel[.panel-name[Road construction and rainfall] .pull-left[ - We analysed rainfall data from two stations of the [Servicio Nacional de Meteorología e Hidrología del Perú (SENAMHI)](https://www.senamhi.gob.pe/). - **75%** of landslides were observed on satellite imagery simultaneously with road construction work. - The remaining **25%** were identified between one week and seven months after the roads had been constructed. - **51%** of the landslides were observed during the wet season (November to April). - **41.1%** occurred during El Niño–Southern Oscillation (ENSO) strong cool phase or “La Niña” period. ] .pull-right[ ![](figs/lucma_landslides_rain_egu.png) ] ] ] --- <div class="my-footer"><span> <a href="http://creativecommons.org/licenses/by/4.0/"><img src="https://i.creativecommons.org/l/by/4.0/88x31.png"height="25px"/></a>                             </span></div> ### Final remarks We observed that the majority of mapped landslides were directly (e.g., landslides resulting from slope undercutting) or indirectly associated with road constructions (e.g., rainfall-induced landslides resulting from a combination of extreme precipitation over slopes with decreased stability) and that the road constructions also may set preconditions for subsequent rainfall-triggered landslides. <img src="figs/P1000529.JPG" width="350px"/> <img src="figs/P1000537.JPG" width="350px"/> <img src="figs/P1000539.JPG" width="350px"/> .footnote[ **Field photos:** © Copyright 2019 Adam Emmer. ] --- <div class="my-footer"><span> <a href="http://creativecommons.org/licenses/by/4.0/"><img src="https://i.creativecommons.org/l/by/4.0/88x31.png"height="25px"/></a>                             </span></div> ### Further work Emmer, A., Hölling, D., Abad, L., Štěpánek, P., Zahradníček, P., Emmerova, I. *Landslides Associated with Recent Road Constructions in the Río Lucma Catchment, Eastern Cordillera Blanca, Peru*. Submitted to Geomatics, Natural Hazards and Risk. ### Acknowledgements This work was supported by the AUT-CZE MOBILITY project ‘Is the occurrence of slope movements in the Cordillera Blanca, Peru, influenced by the El Niño Southern Oscillation?’ (Project No. 8J18AT032 and CZ 04/2018, respectively). Lorena Abad and Daniel Hölbling have also been supported by the Austrian Research Promotion Agency (FFG) through the project MontEO (The impact of mass movements on alpine trails and huts assessed by EO data; contract no. 873667). ### Contact
<i class="fas fa-envelope faa-wrench " style=" color:#006400;"></i> [**lorenacristina.abadcrespo@sbg.ac.at**](mailto:lorenacristina.abadcrespo@sbg.ac.at)
<i class="fab fa-twitter faa-wrench " style=" color:#006400;"></i> [**@loreabad6**](https://twitter.com/loreabad6)
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