Application of Remote Sensing and GIS in soil erosion hazard mapping and land suitability analysis in Phewa watershed - A case study
Objectives
The main Objectives of the study are as follows:
- To perform digital image processing of land sat CCI for land use cover types using ERDAS Software.
- To construct the data base for Geographic information system to digitized the existing maps such as slope soil depth rock out crops , maps with panchayat and sub watershed boundaries.
- To prepare potential soil erosion hazard and land suitability map. from the existing maps using GIS technology.
Study area
The Phewa water shed is located in the Kaski district of the western Development region. the water shed has an area of 12.5 km and drained in to on the Nepal most prominent lakes. the Phewa Lake. the water shed extend from 28 10 29 to 28 16 15 latitudes to 77 47 46 to 77 58 12 longitudes topography of the thr area is steep with the elevation ranging. from 850 to 2500 m from msl.
The climate of the water shed is humid subtropics to humid temperature the mean temperature at the Phokara ranging from 12 to in December and January to 25C in July and August with minimum of about and maximum of about 34 C. Lumle Agricultural Center (1975 m) to the north-west of the watershed has a mean monthly temperature ranging between 3.5 C in January to 20C in August. The average annual train fall in Phewa water shed is about 4000 m in 1979.
In the water shed of the land is intensively used for agricultural purpose .Two types of agricultural can be located land and bari land lost of the Khet land is located on the valley floor the agricultural crops of the Khet land is this area are rice in summer and wheat un winter seasons. Rice Crop in irrigated from streams. Bari land is located on the upper slopes of the water shed the main crops in this area are maize millet it summer and wheat in winter.
The forest vegetation can be located on the higher elevation of the water shed area the main species area quarques semicarpifilia schins castanposis and Ainus sp.
Fig.1.
Material and methodology
- Data Processing
The computer compatible tape was located into the CIPHER TAPE amd the study was displayed on the screen and the study area was located in ( fig.2 ).
- Image Enhancement
Image enhancement is the modification of an image to alter its imapct on the view or to improve the interprętability for a particular purpose .The object on a ground with similar spectral features may not distinguishable on a land sat image because the tone difference can observe by human eye. Therefore enhancement in necessary before classification.
In this study, histogram equilization was performed. This enhances the image displayed on the screen by maximizing the color contrast.
- Mulispectral classification
Multi spectral classification is a type of information extract process that analysis the spectral and assigns the pixels categories based on similar signature before geometric correction rectification of the image was performed a supervised classification was applied to produce a nine classification thematic map of principal of land use cover in the study area on the existing land use map of the study area used as a references .the training data were then used to assign a to each pixel in the study area.
The purpose of classification of the image before geometric correction was to avoid the classification errors contributed by resembling process.
