『Abstract
Soil erosion processes have been studied intensively throughout
the last decades and rates have been measured at the plot scale
as well as larger scales. However, the relevance of this knowledge
for the modelling of long-term landscape evolution remains a topic
of considerable debate. Some authors state that measurements of
current rates are irrelevant to landscape evolution over a longer
time span, as they are inconsistent with some fundamental characteristics
of landscapes, such as the fact that the long-term sediment delivery
ratio needs to be equal to 1 and that extrapolation of current
rates would imply that all soils in Europe should have disappeared
by now (e.g. Parsons, A.J., Wainwright, J., Brazier, R.E., Powell,
D.M., 2006. Is sediment delivery a fallacy? Earth science Processes
and Landforms 31, 1325-1328). In this study, we investigate if
and to what extent estimates of long-term erosion rates are consistent
with information obtained over much shorter time spans for the
Loam Belt of Belgium.
In a first step, observed short-term and long-term patterns in
the Belgian loess area are compared statistically by classifying
the study area into landscape element classes and comparing average
erosion values per class. This analysis shows that the erosion
intensities on the two temporal scales are of the same order of
magnitude for each landscape element class. Next, the spatially
distributed model WaTEM LT (Water and Tillage Erosion Model Long
Term) is calibrated based on the available short-term data by
optimising average erosion values for the same landscape element
classes. Finally, the calibrated model is used to simulate long-term
landform evolution, and is validated using long-term data based
on soil profile truncation. We found that the model allows simulating
landscape evolution on a millennial time scale using information
derived from short-term erosion and deposition data. However,
it is important that land use is taken into account for the calibration
in order to obtain realistic patterns on a longer time scale.
Our analysis shows that, at least for the study area considered,
data obtained on erosion and deposition rates over various temporal
scales have the same orders of magnitude, thereby demonstrating
that measurements of current rates of processes can be highly
relevant for interpreting long-term landscape evolution.
Keywords: water erosion; scale effects; modelling; short-term
erosion data; long-term erosion data; sediment delivery ratio』
1. Introduction
2. Materials and methods
2.1. Study area
2.2. Available data
2.2.1. Short-term erosion and deposition patterns
2.2.2. Long-term erosion and deposition patterns
2.3. Methods
2.3.1. Data classification
2.3.2. Application of the WaTEL LT model
2.3.2.1. Model structure
2.3.1.1. Water erosion
2.3.1.2. Tillage erosion
2.3.1.3. Output data
2.3.2.2. Model implementation
2.3.2.3. Representativity of the calibration data
3. Results
3.1. Data classification
3.2. Application of the WaTEM LT model
3.2.1. Short-term calibration
3.2.2. Long-term validation
4. Discussion
5. Conclusions
Acknowledgements
References