E&ES > Geography > Research projects > Spatial and temporal variations of topsoil resistance against erosion by concentrated flow

Spatial and temporal variations of topsoil resistance against erosion by concentrated flow :
characterisation and modelling

Researcher: Drs. Anke Knapen
Promotor: Prof. Dr. Jean Poesen, K.U.Leuven, Physical and Regional Geography Research Group
Co-promotor: Prof. Dr. G. Govers, K.U.Leuven, Physical and Regional Geography Research Group
Funding: F.W.O. (mandaat aspirant)
Keywords:
topsoil resistance, concentrated flow erosion, ephemeral gully, erosion control strategy
Research abstract:

The objective of this research project is to document and explain the occurrence of landslides in the Flemish Ardennes. Questions to be answered are where and when are landslides initiated or reactivated?, which factors are responsible for this initiation or reactivation? And how important is the damage caused by landslides?
This project includes mapping and classification of the landslides in the field. Next, the information collected in the field will be used in different models in a GIS environment together with environmental characteristics such as geology, rainfall data, soil characteristics, topographic parameters, vegetation and human activity (land use, construction of infrastructure). Information on the timing of landslide initiation or reactivation will be obtained from technical services and local people. More detailed information on displacement rates and the factors influencing this displacement will be obtained by monitoring of two or three landslides.

 

Gully erosion due to concentrated flow, Kamerijk (Gingelom)

Gully erosion due to concentrated flow, Kamerijk (Gingelom), 2002

Introduction

Over the last decades, most research dealing with soil erosion by water has concentrated on interrill and rill erosion processes. Relatively few studies have been conducted on erosion by concentrated flow, which can lead to (ephemeral) gully erosion (Poesen et al., 2003). Nevertheless, ephemeral gullies have been recognized as contributing significantly to total sediment budgets in a range of agricultural environments. In addition, by increasing the connectivity of the landscape, they aggravate the off-site damages such as flooding, silting of reservoirs and pollution of streams.

SEphemeral gully erosion due to concentrated flow, Kamerijk (Gingelom)

Ephemeral gully erosion due to concentrated flow, Kamerijk (Gingelom), 2002


To predict the risk on ephemeral gully erosion accurately, more information about the hydraulic thresholds for the initiation of gully development is needed. Moreover, the soil resistance against erosion by concentrated flow should be determined for different topsoil conditions of Belgian loess soils throughout the year.

Objectives and methods

By improving the knowledge about topsoil resistance against erosion by concentrated flow, this research aims to contribute to a better prediction of spatial and temporal variations of soil erodibility and related soil loss and consequently to a more effective control of the gully erosion problem. The following objectives will be pursued:

1. Comparison of the existing techniques to measure topsoil resistance and the controlling parameters. A literature review.
2. Determination of spatial and temporal variations of topsoil resistance against erosion by concentrated flow in central Belgium. At different moments of the year, soil resistance against concentrated flow will be measured on representative measuring sites in the Belgian Loess belt.
3. Prediction of the resistance against erosion by concentrated flow as a function of soil type, landuse and initial soil moisture content. Texture, dry bulk density, organic matter content, root density, moisture content and shear resistance will be measured on soil samples in search for statistical relations between static and dynamic soil parameters, land use and the measured soil resistance.
4. Improvement of existing concentrated flow erosion models. Existing gully erosion models (e.g. EGEM, Woodward, 1999) only incorporate the effects of aboveground biomass on the runoff hydraulics while the effects of land use on topsoil resistance (by compaction and root systems) are neglected. Using the relations obtained in this study, erosion by concentrated flow will be modelled more accurately due to a better prediction of topsoil resistance.
5. Development of appropriate land use strategies to reduce soil erosion by concentrated flow. Simulations will be conducted to detect the influence of soil type, land use and initial moisture content on the intensity of erosion by concentrate flow in order to predict the best gully erosion controlling strategies for loess soils in central Belgium.

Study area

The topsoil resistance against concentrated flow erosion will be measured at representative agricultural fields in the Belgian Loess Belt, (1) in the municipalities of Sint-Truiden and Gingelom, where farmers are already testing several techniques to reduce erosion by concentrated flow (e.g grassed waterways, flexible dams) and (2) near the city of Leuven where ephemeral gullies are common.

Belgian Loess Belt

 

testing several techniques to reduce erosion by concentrated flow

End products

This research should lead to the following end products:

1. Dataset on topsoil resistance against concentrated flow erosion in central Belgium;
2. Statistical relations between topsoil resistance and land use, tillage operations, soil type and meteorological conditions;
3. Improved gully erosion model, incorporating topsoil resistance;
4. Method to define adequate protective measures to fight (ephemeral) gully erosion by improving topsoil conditions.