Determination Dynamics Models of Erosion Hazard Rates Based on Land Use of Simbelin Sub-Watershed in Dairi District North Sumatera Province

Abstract

A research was conducted at the area of Simbelin sub-watershed in Dairi District, North Sumatra Province, during two rainy and dry seasons from November 2014 up to June 2015. The objectives of the research were are : (1) mapping locations  having similar class of erosion hazard as effect of land use at each polygon of  Simbelin sub-watershed , (2) to obtain accurate measurement of soil  erosion method in relation with  land use at the sub-watershed of Simbelin, and (3) to obtain the simulation model dynamics of soil  erosion through Geographic’s Information Systems analysis for appropriate soil management relevant to land use. The research method used in this study were  descriptive and explorative survey, descriptive method survey in the field by using data of interpreted maps from satellite image and other supported data, where as explorative survey was conducted by determination of soil physical properties and chemical properties by analysis of soil samples  in laboratory.

        Results of research showed that: (1).      Levels  of hazard erosion in sub-watershed of Simbelin based upon land use varied from the light to the very heavies , with very light  hazard erosion  at primary and secondary forests( average of 4,30 tons  ha-1 y-1 and 14,32 tons  ha-1 y-1), light at paddy soil (23,37  tons  ha-1 y-1),   medium  at  small  plantation( 139,50 tons  ha-1 y-1), heavy at settlement ( 388,66 tons  ha-1 y-1), and  very heavy  at agro forestry and non irrigated land  (568,15 tons  ha-1  y-1 and 692,54 tons  ha-1 y-1, respectively); (2). a. Standard erosion plot and sedimentation were accurate methods for measuring soil erosion in relatively small  land area, whereas  Universal Soil Loss Equation (USLE) was the accurate method for  measuring soil erosion in  wide  area,           b.         the average erosion by using sedimentation, standard erosion plot and USLE methods  were 15,93  tons  ha-1 y-1; 28,56 tons  ha-1 y-1, and  368,71 tons ha-1 y-1, respectively;

(3).   a. Value of actual erosion measured by sedimentation or standard erosion plot was different from predicted erosion by Geographic’s Information System (GIS) analysis, namely 15,93  tons  ha-1 y-1; 28,56 tons  ha-1 y-1 , and  339,54 tons  ha-1 y-1, respectively, b. Dynamic analysis models used for measuring soil erosion in wide areas..

Keywords: nynamic models, erosion, land use.