Impact of Inland Bathymetry on Applications. Flood inundation, channel hydraulic geometry and flood flow estimates

Presentation given at TopoBathy Workshop Sept 17-18, 2019, Tuscaloosa, Alabama.

Flood inundation is difficult to map, model, and forecast because of the data needed and the computational demand. Recently an approach based on the relative elevation, or Height Above Nearest Drainage (HAND), which is derived from a digital elevation model (DEM), has been suggested for both flood mapping and obtaining reach hydraulic properties and synthetic rating curves. These products are only as good as the underlying DEM from which they are derived and thus better inland bathymetry offers the potential for incorporating bathymetry into national scale models to improve flood inundation modeling and mapping. This presentation will review the approach for using relative elevation in flood modeling, describing how HAND is calculated, how it is used to map flood inundation for stream reach catchments and how it is used to determine stream reach properties, identifying shortcomings and giving ideas for improvements. As we obtain more detailed information on bathymetry, topography and hydrography it is important to establish a consistent data model for the river bed that is used in HAND related work that aligns and reconciles elevation and hydrography. This presentation will discuss approaches for using hydrography to remove DEM obstacles, the segmentation of streams used in deriving HAND reach average hydraulic properties and ideas for quantifying reach average roughness based on HAND and flood inundation mapped from remote sensing of previous floods with measured discharges.

在2019年9月17日至18日于阿拉巴马州图斯卡卢萨举办的TopoBathy研讨会上，我所作的演讲。由于所需数据和计算需求，洪水淹没的测绘、建模和预测一直是一项艰巨的任务。近期，一种基于相对高程，即最近排水沟以上高程（HAND），的方法被提出，该方法由数字高程模型（DEM）推导而来，可用于洪水测绘以及获取河段水力特性和合成比尺曲线。这些产品仅与推导它们的底层DEM相当，因此更精细的内陆地形测量为将地形测量融入国家级模型以改善洪水淹没建模和测绘提供了潜在可能。本次演讲将回顾利用相对高程进行洪水建模的方法，阐述如何计算HAND，如何利用它为溪流河段集水区绘制洪水淹没图，以及如何用它确定河段特性，并指出其不足之处，并提出改进建议。随着我们获取更多关于地形、地貌和水文的信息，建立一个一致的数据模型对于河流床面至关重要，该模型用于与HAND相关的工作，以协调和调和高程与水文数据。本次演讲将讨论利用水文数据消除DEM障碍的方法，HAND河段平均水力特性的推导所用的溪流分割，以及基于HAND和以前洪水遥感测绘的洪水淹没以及测量流量来量化河段平均粗糙度的想法。