6-Soil Loss Prediction Equations.

Abstract

Runoff is the main carrier of eroded soil as sediment washload in a fluvial system. Increasingly, prediction of sediment yield is becoming important for design and operation of reservoirs, water supply systems, sediment and flood control projects, & sediment pollution control. Suspended sediment yield (washload) models are still in a stage of their infancy.Recently some studies on diterministic, probablistic and stochastic processes have been carried out to model the suspended sediment yield process. The presently developed models can be catagorised into four main groups, namely, (1)Satistical regression models, (2) System models represented by unit sediment graph approach (3) Parametric sediment routing models, and (4) Stochastic and dynamic models. Sedimentation is the detachment, entrainment transportation and deposition of of eroded soil. Most of the damage to the ecosystem is caused by accelarated erosion of soil which is in excess of geologic norm. Rainfall on bare land surface initiates the process of erosion. Thus, to begin with, regression models with rainfall as the input were developed. Later, it was observed that the runoff is a better predictor of sediment yield than the rainfall. Since runoff is the main carrier of washload, it was further observed that the hydrological properties of the two are the same. This brought in the concepts for application of system models and parameteric models on sediment yield, based on the techniques as used for runoff models. Similarly,' stochastic and dynamic models were also successfully developed to predict sediment yield. In this paper an attempt has been made to critically review the recent work on soil erosion and sediment yield models and present them in a catagorised form.