Evaluation of C and P Factors in Universal Soil Loss Equation on Trapping Sediment: Case Study of Santubong River

Kelvin K K Kuok,Darrien Y S Mah,P C Chiu

doi:10.4236/jwarp.2013.512121

Abstract

Universal Soil Loss Equation (USLE) is the most comprehensive technique available to predict the long term average annual rate of erosion on a field slope. USLE was governed by five factors include soil erodibility factor (K), rainfall and runoff erodibility index (R), crop/vegetation and management factor (C), support practice factor (P) and slope length-gradient factor (LS). In the past, K, R and LS factors are extensively studied. But the impacts of factors C and P to outfall Total Suspended Solid (TSS) and % reduction of TSS are not fully studied yet. Therefore, this study employs Buffer Zone Calculator as a tool to determine the sediment removal efficiency for different C and P factors. The selected study areas are Santubong River, Kuching, Sarawak. Results show that the outfall TSS is increasing with the increase of C values. The most effective and efficient land use for reducing TSS among 17 land uses investigated is found to be forest with undergrowth, followed by mixed dipt. forest, forest with no undergrowth, cultivated grass, logging 30, logging 10^6, wet rice, new shifting agriculture, oil palm, rubber, cocoa, coffee, tea and lastly settlement/cleared land. Besides, results also indicate that the % reduction of TSS is increasing with the decrease of P factor. The most effective support practice to reduce the outfall TSS is found to be terracing, followed by contour-strip cropping, contouring and lastly not implementing any soil conservation practice.

Highlights

Buffer zone is the vegetation area including trees, grasses and bushes adjacent to streams, rivers, creeks or wetlands [1]
The predicted outfall Total Suspended Solid (TSS) for different future land uses are ranging from −161 mg/L to 7571 mg/L, and predicted % reduction of TSS are ranging from 3% to 514%
Negative values obtained for outfall TSS especially from cultivated grass, forest with no undergrowth, mixed dipt. forest and forest with undergrowth, indicate that the buffer is able to reduce the TSS effectively and efficiently until there is no outfall TSS produced in the study area

Summary

Introduction

Buffer zone is the vegetation area including trees, grasses and bushes adjacent to streams, rivers, creeks or wetlands [1]. The aim of Buffer zone is to remove sediment and other pollutants from surface water runoff through filtration, deposition and infiltration processes [1]. Buffer zone is usually introduced to protect water bodies by slowing and reducing the surface runoff, and allows it to be absorbed by the ground to prevent flooding, and provides habitat for wildlife and enhances the aesthetics of the surroundings. Best Management Practices (BMPs) such as grass buffer strips, vegetative filter strips, riparian buffer zones, grass waterways, have been suggested as potential controls to help reduce erosion and offsite transport of sediments. Vegetated buffers show a positive effect on reducing the transfer of sediments, nutrients and pesticides to surface waters [2,3]

Methods

Results

Conclusion