Assessment of the effects of DEM gridding on the predictions of basin runoff using MIKE SHE and a modelling resolution of 600 m

Abstract

Summary A 586-km 2 catchment was modelled with the distributed hydrologic model MIKE SHE. Coarse digital elevation models (DEMs) having a 600-m resolution and gridded from a set of elevation points geographically distributed with a much finer resolution were used in the modelling with the purpose of investigating potential effects of the DEM generation methods on (i) model parameter values; (ii) adequacy of model global predictions; and (iii) the evaluation of internal state predictions. To address these aspects, this paper describes the DEM gridding methods, assesses the accuracy of the DEMs and examines systematically the sensitivities of parameter values and predictions of the distributed model with respect to the DEMs. Three types of gridding methods were applied. Methods type I were based on the use of the MIKE SHE interpolation tool (Bilinear algorithm) for processing input elevation data distributed about the periphery of the gridded DEM cells. Input elevation data distributed about the centre of the gridded DEM cells were processed in gridding methods type II. The third type was based on the use of the TOPOGRID algorithm that considers landscape features, such as digitised streams, to improve the drainage structure of the gridded DEMs. A multi-criteria protocol was applied for assessing the elevation quality of DEMs and their suitability for hydrologic purposes. It was found that the quality of the DEM products of the MIKE SHE interpolation tool were poorer. The independent calibration of the assembled hydrologic models revealed (i) important variations of model predictions; and (ii) from average to important variations of effective parameter values, as a function of the different DEMs. A multi-criteria protocol analysing discharge time series, peak flows and piezometric levels showed that model performance is in broad terms in agreement with the elevation and slope quality of the DEMs.