This blog post continues the contribution from Patrick Bergeron, who describes a floodplain delineation using only ArcHydro models, focusing on a simple 1-river/1-gauge station system (http://blogs.esri.com/esri/arcgis/2014/03/17/floodplain-delineation-using-only-arc-hydro-models/). This blog additionally gives some explanations regarding the processing, including possible problems and solutions. See also the attached workflow.
The same ArcHydro models (Stream WSE From Point Measurements; Flood From Stream WSE) were applied to a medium-sized catchment area (721 km²) in southern Germany, in which both the principal stream as well as two tributaries were considered. Three gauge stations are located on the principal stream, and one station is located on each of the tributaries. The required DEM has a resolution of 25 m.
Required information for the gauge stations is stored in the Time Series table. This includes the water stream elevation values (WSE, TSValue), the time of measurement (TSTime), and the Variable ID (VarID), which is defined by a simple ‘VariableDefinition’ table. Furthermore, a Feature ID is required, which has to be the same as the Hydro ID of the vector data set for the gauge stations to assign the information to the spatial location. It should be noted that errors can occur due to incorrect data types of the table fields.
The WSE are essential for the creation of 3D-Lines (Stream WSE From Point Measurements), and must be based on the elevation of the DEM at the gauge station (results see blue lines in the 3D-ArcScene illustration). Due to the poor resolution of the input DEM, WSEs which reference the gauge datum can differ greatly from the DEM elevations, leading to a large height discrepancy between the WSEs and the DEM. Hence, referencing to the gauge datum can cause errors in the creation of the 3D-Lines, particularly at the junction of two streams (see gaps at the junction of the red lines).
Overall, delineation of the flooded area and flood depths was also successful for more complex input data. However the low spatial resolution of the DEM results in cornered flood areas.
Thomas Bueche, Department of Geography, University of Munich
Stefan Weinberger, ESRI Germany
Mark Vetter, Faculty of Information Management and Media, University of Applied Sciences