Dynamic flood topographies in the Terai region of Nepal

Flood hazard maps used to inform and build resilience in remote communities in the Terai region of southern Nepal are based on outdated and static digital elevation models (DEMs), which do not reflect dynamic river configuration or hydrology. Episodic changes in river course, sediment dynamics, and...

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Bibliographic Details
Published in:Earth surface processes and landforms 2020-10, Vol.45 (13), p.3092-3102
Main Authors: Dingle, E.H., Creed, M.J., Sinclair, H.D., Gautam, D., Gourmelen, N., Borthwick, A.G.L., Attal, M.
Format: Article
Language:English
Subjects:
Accretion
Aggradation
Alluvial channels
Alluvial rivers
bifurcation
Bifurcations
channel mobility
Delft3D
Digital Elevation Models
Discharge
Earth surface
Elevation
Flood discharge
Flood hazards
flood inundation
Flood mapping
Flood predictions
Flooding
Floodplains
Floods
Fluvial sediments
Hazard assessment
Hydrodynamics
Hydrology
Landforms
Nepal
Population density
Prediction models
River channels
River systems
Rivers
Sediment
Sediment dynamics
Sediment load
Sediments
Two dimensional models
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Summary:Flood hazard maps used to inform and build resilience in remote communities in the Terai region of southern Nepal are based on outdated and static digital elevation models (DEMs), which do not reflect dynamic river configuration or hydrology. Episodic changes in river course, sediment dynamics, and the distribution of flow down large bifurcation nodes can modify the extent of flooding in this region, but these processes are rarely considered in flood hazard assessment. Here, we develop a 2D hydrodynamic flood model of the Karnali River in the Terai region of west Nepal. A number of scenarios are tested examining different DEMs, variable bed elevations to simulate bed aggradation and incision, and updating bed elevations at a large bifurcation node to reflect field observations. By changing the age of the DEM used in the model, a 9.5% increase in inundation extent was observed for a 20‐year flood discharge. Reducing horizontal DEM resolution alone resulted in a
ISSN:0197-9337
1096-9837
DOI:10.1002/esp.4953