28 Dec 2020

28 Dec 2020

Review status: this preprint is currently under review for the journal HESS.

Effects of spatial resolution of terrain models on modelled discharge and soil loss in Oaxaca, Mexico

Sergio Naranjo1,2, Francelino A. Rodrigues Jr.1, Georg Cadisch2, Santiago Lopez-Ridaura1, Mariela Fuentes3, and Carsten Marohn2 Sergio Naranjo et al.
  • 1International Maize and Wheat Improvement Center (CIMMYT), Texcoco, 56237, Mexico
  • 2Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg Institute), Stuttgart, 70599, Germany
  • 3Universidad Autonoma Metropolitana-Xochimilco, Mexico City, 04960, Mexico

Abstract. The effect of spatial resolution of digital terrain models (DTM) on topography and soil erosion modelling is well documented for low resolutions. Nowadays, the availability of high spatial resolution DTM from unmanned aerial vehicles (UAV) opens new horizons for detailed assessment of soil erosion with hydrological models, but effects of DTM resolution on model outputs at this scale have not been systematically tested. This study combines plot scale soil erosion measurements, UAV-derived DTM, and spatially explicit soil erosion modelling to select an appropriate spatial resolution based on allowable loss of information.

During 39 precipitation events, sediment and soil samples were collected on five bounded and unbounded plots and four land covers (forest, fallow, maize, and eroded bare land). Additional soil samples were collected across a 220 ha watershed to generate soil maps. Precipitation was collected by two rain gauges and vegetation was mapped. Two UAV campaigns over the watershed resulted in a 0.60 m spatial resolution DTM used for resampling to 1, 2, 4, 8, and 15 m; and a multispectral orthomosaic to generate a land cover map. The OpenLISEM model was calibrated at plot level at 1 m resolution and then extended to the watershed level at the different DTM resolutions.

Resampling the 1 m DTM to lower resolutions resulted in an overall reduction of slope. This reduction was driven by migration of pixels from higher to lower slope values; its magnitude was proportional to resolution. At the watershed outlet, 1 and 2 m resolution models exhibited the largest hydrograph and sedigraph peaks, total runoff and soil loss; they proportionally decreased with resolution. Sedigraphs were more sensitive than hydrographs to spatial resolution, particularly at the highest resolutions. The highest resolution models exhibited a wider range of predicted soil loss due to their larger number of pixels and steeper slopes. The proposed evaluation method showed to be appropriate and transferable for soil erosion modelling studies, indicating that 4 m resolution (< 5 % loss of slope information) was sufficient for describing soil erosion variability at the study site.

Sergio Naranjo et al.

Status: open (extended)
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Sergio Naranjo et al.

Sergio Naranjo et al.


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Short summary
This study pioneers in the integration of a spatially explicit soil erosion model with plot and watershed scale characterization and high resolution drone imagery to assess the effect of spatial resolution DTM on discharge and soil loss. Results showed reduction of slope due to resampling-down of DTM. High resolution translates into higher slope, denser fluvial system, and extremer values of soil loss reducing time of concentration and increasing soil loss at the outlet. Best resolution was 4 m.