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.
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.
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.
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.
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.
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.
- 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.
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.