A hydraulic model of the Amur River informed with ICESat-2 elevation

Abstract Accurate predictions of water surface elevation (WSE) in rivers at high spatial and temporal resolution are important for flood/drought risk assessment and flood/drought forecasting and management. River WSE is the key parameter controlling inundation of the areas surrounding the river, river navigability and water availability, e.g. for cooling purposes and hydropower. WSE in a river is controlled by three main factors: discharge, riverbed geometry, and hydraulic roughness. In well-monitored rivers, discharge and riverbed geometry are known from in-situ monitoring stations and geodetic surveys, respectively, while effective hydraulic roughness is typically determined using inverse hydraulic modelling techniques. In remote and poorly instrumented rivers, both discharge and riverbed geometry are highly uncertain and WSE is therefore hard to predict. ICESat-2 laser altimetry provides accurate elevation transects across the river at very high spatial resolution (70 cm along track). Globally available digital elevation models have 30m resolution and ICESat-2 laser altimetry thus resolves river cross section geometry at a much higher level of detail and accuracy. This paper demonstrates how ICESat-2 elevation transects can be used to parameterize a basin-scale hydraulic model of a major river. The workflow is demonstrated for the transboundary Amur River in North-East Asia. Simulated WSE is subsequently validated against a large dataset of in-situ and satellite altimetry observations and we demonstrate that the model can reproduce available WSE observations throughout the basin with acceptable accuracy.