『Abstract
Basin sediment yield is the product of all sediment producing
processes and sediment transport within a basin. Consequently,
the prediction of basin sediment yield should take into consideration
all different erosion and sediment transport processes. However,
traditional physics-based, conceptual, and empirical or regression
models have not been able to describe all these processes due
to insufficient systems knowledge and unfeasible data requirements.
Therefore, the applicability of these models at the basin scale
is troublesome.This paper first illustrates the relation between
basin area, dominant erosion processes, and sediment yield by
a combination of measured sediment yield at different spatial
scales in Mediterranean environments. This clearly reveals that
soil erosion rates measured at one scale are not representative
for sediment yield at another scale level. Second, the most important
semi-quantitative models developed for erosion and sediment yield
assessments at the basin scale are reviewed. Most of these models
use environmental factors to characterise a drainage basin in
terms of sensitivity to erosion and sediment transport. Six of
the nine models discussed (PSIAC, FSM, VSD, Gavrilovic, CSSM,
WSM) include sheet-, rill-, gully, bank erosion, landslides, and
connectivity, at least partly, in the assessment of basin sediment
yield. The low data requirements and the fact that practically
all significant erosion processes are considered makes them especially
suited for estimating off-site effects of soil erosion. The other
three models (EHU, CORINE, FKSM) focus mainly on sheet and rill
erosion and provide quantitative descriptions of the sensitivity
to erosion at basin or even regional scales. These models thus
focus mainly on on-site problems of soil erosion. Most of the
semi-quantitative models might benefit from a more quantitative
description of factors used to characterise the basin. Though
an equilibrium should be found between the extra effort and increase
in model performance, the increased availability of spatially
distributed topographic data as well as high-resolution satellite
imagery will probably make this feasible in the near future.
Keywords: modelling; sediment yield; soil erosion; sediment delivery;
scale; Mediterranean』
1. Introduction
2. The scale dependency of sediment yield data
2.1. Field data
2.2. A conceptual model of sources, sinks, and scale dependency
of sediment yield
3. Semi-quantitative models for prediction of sediment yield at
the basin- or regional scale
3.1. Introduction
3.2. Pacific Southwest Inter-Agency Committee (PSIAC)
3.3. Factorial scoring model (FSM)
3.4. The vegetation-surface material-drainage density model (VSD)
3.5. The Gavrilovic model
3.6. Erosion hazard units (EHU)
3.7. CORINE erosion risk maps
3.8. Coleman and Scatena scoring model
3.9. Fleming and Kadhimi scoring model (FKSM)
3.10. Wallingford scoring model
3.11. Global land degradation assessments
4. Synthesis: modelling and understanding sediment yield at the
basin scale
5. Conclusions
Acknowledgements
References