Methodology for Applying GIS to Evaluate Hydrodynamic Model Performance in Predicting Coastal Inundation

Abstract

Reid, S.K.; Tissot, P.E., and Williams, D.D., 2014. Methodology for applying GIS to evaluate hydrodynamic model performance in predicting coastal inundation.Accurate inundation predictions are critical to habitat conservation, littoral boundary definition, and coastal planning. Validating a hydrodynamic model against field observations is essential for evaluating model performance. The output of a typical hydrodynamic model provides georeferenced predictions that can be used to delineate a wet/dry boundary. This paper presents two geospatial methods that complement in-situ point-based validation. The methods utilize the Coastal Modeling System (CMS) hydrodynamic model and ArcMap software. In general, the techniques are applicable to other calibrated hydrodynamic models and may be applied independently or in conjunction. Each method was validated with an extensive data set available for tidal flats located along Packery Channel, Texas. Method 1 compared model predictions to the observed conditions of high-resolution aerial and satellite imagery, which were classified using one of two geospatial processes. Method 2 applied the model output to delineate the maximum flood extent and then compared the predicted extent to topographic surveys, which define the true time-dependent flood line. Method 1 was applied to 11 test cases for which reliable high-resolution aerial and satellite imagery was available, while method 2 was based on five topographic surveys. The hydrodynamic model was well calibrated, with average absolute errors ranging from 0.026 to 0.125 m/s for current predictions. Analyses quantified agreement between model predictions and classified imagery ranging from 69% to 91%. This methodology expands present capabilities to assess and improve hydrodynamic model predictions, particularly for inundation delineation in shallow coastal environments and coastal settings strongly influenced by nontidal factors such as wind.