Determination of Soil Erodibility, K Factor for Sungai Kurau Soil Series

Many incidence of landslides and erosion have occitred in Malaysia lately, especially in the highlands areas, properties were damaged and lives were lost. Seeing the need of resolving and minimizing such untoward incidence, therefore study on soil erosion is needed. Most of the soil erosion studies done by researchers were based on the Universal Soil Loss Equation (USLE) (Wischmeier Smith, 1978) as a method to predict the soil loss. USLE take into account several factors such as rainfall, soil erodibility, slope, land cover and erosion control practice for soil erosion prediction. However, this study mainly focused on soil erodibility, K factor for various types of soil series in Malaysia. Soil erodibility is an important index to measure soil susceptibility to water erosion, and an essential parameter needed for soil erosion prediction. The major aims of this study is; a) to determine soil erodibility based on nomographs and other estimating methods and b) to develop soil erodibility map using GISfor a selected case study. The data obtained from DOA for various soil types is used in this study and verification is made based on Relative K values studied by Tew in 1996. The performance of each method is analysed using statistical analysis such as Root Mean Squared Error (RMSE) and average error. The value of erodibility was found to be the greatest in equation developed by Rousseva method, with K value in the range of 0.0167 to 0.0821 ton h (MJ mm)^-1,while Tew equation generate the smallest value, which is in the range of 0.0013 to 0.0557 ton h (MJ mm)^-1. Tew equation also indicates the smallest error which is 0.0189 and 0.0129 for RMSE and average error respectively, therefore, suggesting it to be the most applicable method for statistical determination of soil erodibility for Malaysian soil series.