Dr Ingrid Takken - PhD Research

PhD Research

My PhD research was part of a project of the European Union on ‘Effective Land Management for Surface Runoff Control’. This project aimed at the improvement of a spatially distributed soil erosion model (LISEM) in order to develop a land management tool for runoff control in agricultural areas.

As a first part of my PhD research I performed a spatial validation of LISEM, which highlighted that the model poorly predicted spatial patterns of erosion and deposition. Amongst the possible reasons that identified for this were incomplete or incorrect process descriptions as well as a wrong representation of flow directions within the model (Takken et al., 1999). To contribute to model improvement, my further PhD research focussed on the effects of soil roughness on runoff and erosion at different scales.

At laboratory scale, it included flume experiments to study the effects soil roughness on the hydraulics of rill and interrill flow (Fig.1). One of the outcomes of this work was a model that can be used to predict the hydraulic resistance of (bare) interrill surfaces (Takken and Govers., 2000).

Fig.1: Flume experiments at the Laboratory for Experimental Geomorphology, K.U.Leuven

At the catchment scale, I studied the effects of oriented roughness caused by linear landscape features such as tillage lines and parcel borders on runoff flow directions. These linear features can cause runoff to flow in other directions than the topographic direction, which proved to have important effects on both runoff and erosion patterns (Fig.2).

 

Fig.2: Effects of tillage lines and parcel borders on runoff flow directions and erosion

I used field data to develop the Tillage-Controlled Runoff Pattern model (TCRP), which is a model that is capable of predicting a runoff pattern, taking into account the effects of tillage lines and parcel borders. This model includes a logistic regression equation to predict the flow direction (either topographic or tillage direction) and a series of GIS algorithms to create a sound raster flow pattern, presenting the predicted directions. Implementation of this runoff pattern in spatially distributed soil erosion models resulted in much better predictions of observed erosion patterns (Fig.3; Takken et al., 2001a and b). The GIS algorithms are written in the PCRaster language are freely downloadable from the K.U.Leuven website:http://www.kuleuven.ac.be/geography/frg/leg/index.htm

 

Fig.3: Observed and predicted erosion patterns (ton/ha) for a 4.4 ha field in the Belgian loess belt. A: Using a topographic runoff pattern. B: Using the tillage-controlled runoff pattern. Takken et al., 2001.

Finally, a series of model runs was carried out to evaluate to what extent the predictions of the spatially distributed erosion model LISEM are affected by the description of the hydraulic resistance, the parameter values used to characterize hydraulic resistance as well as the routing algorithm used to generate the runoff pattern. This highlighted that the process description used for overland flow resistance and velocity has a clear effect on the erosion and deposition rates predicted by the model. However, relatively minor variations in a single parameter value (hydraulic roughness) appear to affect model output more strongly than variations in the process description itself. The use of different routing algorithms leads to notably different erosion and deposition patterns, while total erosion and deposition rates were much less affected (Takken et al., in press).

References:

Takken, I., Beuselinck, L., Nachtergaele, J., Govers, G., Poesen, J. and Degraer, G., 1999. Spatial evaluation of a physically-based distributed erosion model (LISEM). Catena, 37, 431-447.

Takken, I. and Govers, G, 2000. Hydraulics of interrill overland flow on rough, bare soil surfaces. Earth Surfaces Processes and Landforms, 25, 1387-1402.

Takken, I., Govers, G., Steegen, A., Nachtergaele, N. and Guérif, J., 2001a. The prediction of runoff flow directions on tilled fields. Journal of Hydrology, 248, 1-13.

Takken, I., Jetten, V., Govers, G., Nachtergaele, N. and Steegen, A., 2001b. The effect of tillage-induced roughness on runoff and erosion patterns. Geomorphology, 37, 1-14.

Takken I., Govers G., Jetten V., Nachtergaele J., Steegen A and Poesen J., (in press). The influence of both process descriptions and runoff patterns on predictions from a spatially distributed soil erosion model. Earth Surface Processes and Landforms.