Application of Remote Sensing and GIS in soil erosion hazard mapping and land suitability analysis in Phewa watershed - A case study
Krishna P. Pradhan
Scientist Agronomist
Nepal Remote Sensing Centre
Kathmandu Nepal
Abstract
The object of the study project is to demonstrate the application of land sat image processing and geographic information system in potential soil erosion hazard mapping and land suitability analysis even in the absence of very detailed information about the area .
The land sat computer compatible tape of Phewa water sand from July 1979 was made available through UNITAR from Thailand Receiving station the digital image Processing was done in IBM PC using image Processing modules of EDAS Software Supervised classification technique was applied to extract land use cover information was the water sand .The image was dereferences taking ground control in the water sans units from 1:25000 scale topographical map of the water sand the cell size of 57 m was decided in order to obtained the same size with other GIS profiles.
The existing maps Such as slope soil depth rock out crop were digitized in ARC vector mode systems the vector mode files from were converted in to raster using ARC /INFO command .Which creates in to a GRID with single variable file from polygons in ARC/INFO coverage and these data were transferred in the computer compatible tape all the files were stored in the IBM PC hard disk using the command DT Tape all the files rastarized using the same cell size of 57 meter as image in order to over lay exactly one another.
The final map resulted from the image classification was combined with slope map to obtain of run off rate in the water shed .
Due to the lack of very detailed data a very simple model was applied and prepare potential soil erosion hazard map. the following maps .i.e slope cover slope run off population and soil maps were combined five images of erosion rates were identified in the water shed . the following maps soil quality moisture availability rock outcrop and potential soil erosion hazard were overlaid each other to prepare land suitability for agriculture .
The results obtained from this study can be served as a good example of application of remote sensing and Geographical information system for potential soil erosion hazard mapping and land suitability analysis this type of work can be done in any part of the country once the data are GIS format it can be retrived and manipulated at anytime.
Introduction
The basic needs of the people are food grains fuel wood and timber. The main emphasis should be given to the production of the food grains fulfill the basic need . There is no sufficient supply of food grains to fulfill the demand of the present population .to meet the demand of the population, it has been necessary to extend the agricultural land destroying the forest land .The high rate of deforestation may leads to the desertification of the area and erosion of soil by water which effect the environment and the productivity of land.
The main reason of soil erosion are high precipitation high run off due to the steep slopes high population pressure on 1 land and clearing natural vegetation.
Phewa lake which is located in the Phewa water shed is on the most prominent lakes in Nepal .it is remained un charged by the enthroned the land it receives about 10 ton of sediment the soil erosion which affect on the natural beauty as well as the life the lake it has been pointed pout that the soil erosion losss from grazing land is 174682 ton and from agricultural land.
In the present study a Geographical information system technology was applied to amp the potential soil erosion hazard and the land suitable and remote sensing data.
This type of study helps to locate the areas more vulnarable to soil erosion prone areas are located on the map then it is easy to make plane for better management of land such as afforestation plan terracing of agricultural land etc.
