Thesis colloquium Yvonne Smit

A laboratory experiment with two artificial hillslopes, to investigate the effects of macropores on runoff processes inside a hillslope.

Organisator Hydrology and Quantitative Water Management

ma 25 augustus 2014 13:00 tot 14:00

Locatie Lumen, building number 100
Droevendaalsesteeg 3a
6708 PB Wageningen
+31 317 481 700
Zaal/kamer Lumen 1

The Influence Of Macropores On Runoff Processes Inside A Hillslope

Understanding hillslope runoff response to intense rainfall is an important topic in hydrology, and key to correct prediction of extreme stream flow, erosion and/or landslides. Although it is known that preferential flow processes activated by macropores a are an important phenomena in understanding runoff processes inside a hillslope, hydrological models have been slower to embrace the concept of an extra parameter that represents ‘macropores' because of the complexity of the phenomena. Therefore, it is relevant to investigate the influence of macropores on runoff processes in an experiment in a small artificial hillslope. In this controlled environment it is possible to particularly investigate the influence of macropores where no assumptions have to be made. This research aims to do so. Two identical hillslopes were designed between which the only difference was that one hillslope did not have macropores and the other hillslope did have macropores. Twelve artificial rainfall events were applied to the two hillslopes and results of drainage and soil moisture were investigated. After the experiments it could be concluded that water was flowing through the artificial macropores but no influence on runoff processes were observed during this research. The S90 sand used for this research had typical characteristics that omitted the influence of macropores. It caused runoff to respond too fast to rainfall. Therefore the recession part of drainage could not be accurately investigated. Due to heterogeneous spatial and temporal rainfall intensity the wetting phase of the drainage data was unusable. The pendular water, which was visible in the soil moisture data, could mean the soil has a low air entry value and in combination with the lack of vertical flow that could have caused the pressure difference between the matrix and the macropores to vanish sooner and equilibrium reached in a relatively short time, the influence of macropores on drainage was minimal.