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Geomorphologic & land use planning for Danda watershed
Landuse Mapping
Landuse map has been prepared from digital analysis of satellite data using Earth Resources Data Analysis System (ERDAS) Imagine 8.3.1. For generation of landuse map of the area, IRS-1C LISS-III data and PAN data of scene 96/50 for November 1997 was used. Since the area of watershed is small, the LISS-III scene was merged with PAN scene after carrying out geometric corrections on both of the scenes. The merged scene was re-sampled at 6-metre pixel resolution to get multi-spectral information at 6-metre resolution. Seven classes of landuse i.e. agriculture, fallow, irrigated agriculture, forest, shrubs, open scrub, shrubs and wasteland have been identified in the watershed. Landuse statistics of the watershed is given in Table 2.
Soil Mapping In Garhwal area, the majority of soils are diluvial in nature. Most of the agricultural soils usually lose the top horizon either due to construction of terraces or erosion. In the terraced hillside, the downslope drift of mineral matter is sharply reduced and the soil is stabilised. On steep slopes, soils are generally shallow and usually have a thin surface horizon and medium to coarse texture. Sub-soils are deep and heavily textured. Top surface horizon with a high content of organic matter is a characteristic feature of the area. These soils are highly leached and acidic in nature. Valley soils are developed from the colluvium brought down from the upslopes. Soils of the valley bottom on river terraces comprise of alluvium, brought and deposited by rivers in the process of aggradation. Soil map of the area is derived from supervised classification of the satellite data in conjunction with limited field data collected from field visits and general information collected from the villagers, and the block office. Analysis The linking of the geomorphological parameters with the hydrological characteristics of the basin provides a simple way to understand the hydrologic behaviour of the different basins particularly of the ungauged basins. Before taking up the studies related with hydrologic simulations using the geomorphologic characteristics, the important geomorphological properties have to be quantified from the available topographical map of the basin. The geomorphological properties which are important from the hydrological studies point of view include the linear, aerial and relief aspect of the watersheds. Detailed definitions and description of various geomorphological parameters can be found in Chow (1964) and Singh (1992). The mapping of drainage pattern can be carried out using satellite data. Computation of the parameters required for morphometric analysis using manual methods like area measurement using dot grid method or using planimeter and length measurement using curvimeter are very tedious and time consuming. It is more difficult if the map is on higher scale like 1:50,000 and 1:25,000. The ordering, lengths, area and perimeter etc. can be easily estimated using Geographic Information System (GIS) technique. Use of GIS can not only make this task relatively easy but accurate as well. For quantification of various geomorphological parameters of Danda watershed, the digitised drainage and interpolated contours maps were used. Important parameters thus derived by GIS analysis are listed in Table 3.
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