Flood inundation modelling using the Surface Water Ocean Topography Mission

Over the last few decades flood risk management has become increasingly reliant on simulation of flood inundation from physical models of river-floodplain systems. Information from these models takes the form of flood extent and depth maps, and can directly influence decisions in sectors such as humanitarian response, insurance and urban planning. However,  it is expensive to create accurate models, due to input data requirements, resulting in relatively low-quality simulations along most rivers. One of the major issues is river bathymetry (the land below the water surface) because this cannot be measured remotely and at a large scale.

One way to overcome this issue would be to develop ‘inverse’ models that estimate bathymetry from water surfaces, which are much more observable. In the past, suitable water height measurements have been a limiting factor, however, the Surface Water and Ocean Topography mission will for the first time measure all global river water surfaces wider than ~50 m. This paper develops methods to estimate river bathymetry from SWOT data, evaluating the SWOT height observations and river bathymetry estimates for a small (40-70m wide) UK river. SWOT data is sufficiently accurate to estimate bathymetry that when used for flood modelling could simulate flood extents and depths with similar accuracy to a traditional model based on local river survey data.