Error Assessment for Height Above the Nearest Drainage Inundation Mapping

This is the repository for the paper \"Error Assessment for Height Above the Nearest Drainage Inundation Mapping\" by Lukas Godbout, Jeff Y. Zheng, Sayan Dey, Damilola Eyelade, David Maidment, and Paola Passalacqua. Please direct all communication to [e-mail].

Real time flood inundation mapping is vital for emergency response to help protect life and property. Inundation mapping transforms rainfall forecasts into meaningful spatial information that can be utilized before, during and after disasters. While inundation mapping has traditionally been conducted on a local scale, automated algorithms using topography data can be utilized to efficiently produce flood maps across the continental scale. The Height Above the Nearest Drainage (HAND) method can be used in conjunction with Synthetic Rating Curves (SRCs) to produce inundation maps, but the performance of these inundation maps needs to be assessed. Here we assess the accuracy of the SRCs and calculate statistics for comparing the SRCs to rating curves obtained from hydrodynamic modeling calibrated against observed stage heights. We find that SRCs are accurate enough for large scale approximate inundation mapping while not accurate when assessing individual reaches or cross sections. We investigate the effect of terrain and channel characteristics and observe that reach length and slope predict divergence between the two types of rating curves, and that SRCs perform poorly for short reaches with extreme slope values. We propose an approach to recalculate the slope in Manning’s equation as the weighted average over a minimum distance and assess accuracy for a range of moving window lengths.