Case Study Kenya

This MSc-thesis project in 2002 focussed on the impossibilities and sensitivities of landscape modeling using low resolution and medium quality data.

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In an arid area in Eastern Kenya close to Embu, existing data had low resolution and accuracy. Data for running, calibrating and validating LAPSUS, including the DEM, were manually collected in a regular 125m grid for two research areas of approx. 7.5 km2 each. Methods for additional data collection were simple: infiltration was measured by doing fifteen minutes, 20 cm2 infiltration tests; soil erodibility was estimated with the aggregate stability test. For calibration and validation purposes, actual erosion and sedimentation were estimated as a percentage of the surface for each grid cell.

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LAPSUS Application

The research was successful in the sense that data for running LAPSUS were collected in challenging conditions. Hand-measuring a Digital Elevation Model with a GPS unit was particularly problematic.

Results

Calibration and validation efforts were not very successful, with the two most important reasons being a too large resolution of the DEM and large uncertainty in calibration data. R-square value (cell-by-cell) of the best calibration was 0.47.

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Sensitivity analysis of the results focussed on both patterns and values of model outputs. Sensitivity to multiple flow parameter p was lowest, and sensitivity to transport capacity parameters m and n was highest.

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Different higher-resolution DEMs were interpolated from the field-measured DEM. LAPSUS runs with these DEMs were planned to find out which DEM interpolation method performed better, but LAPSUS (2002) could not handle the sinks created by interpolation.

Publications

  • Temme, A.J.A.M., 2002, The impossibilities and sensitivities of using a landscape model with low resolution and medium-quality data: a case study in East-Kenya: Thesis report.

» more LAPSUS Publications.

Future research

This case study started the drive for a version of LAPSUS that could deal with sinks in a DEM. Sinks are not necessarily mistakes and can represent true landscape features.

» more about how LAPSUS currently deals with sinks.