The Estimation and Mapping of Torrential Risk for Soil and Water Resource Management in Chenab Catchment

Abstract

The cortex of earth can be contemplated as a geomorphic feature, which is the foremost result of apposite endogenic and exogenic forces. The impact of such exogenic forces can be inferred with a ramified arithmetic digit, noted as the morphometric indices, frequently explicated for tectonic characterization. The correlation of these numeric outcomes with the physiographic condition of the area can help to reveal its immediate and genetic scenario. The present research is an attempt to study the implication of these morphometric parameters on geological and hydrological parameters to elucidate the areas prone to surface erosion at the catchment level. The parameters have been calculated up to the 7th order Chenab River basin. This east-west elongated basin has low permeability in northern and southern parts with a scattered erosional pattern. High asymmetry factor (up to 74) and low valley floor to width ratio (≤ 0.01) values of the basin indicates that the basin is tectonically active while the controlled drainage pattern is revealed by the parameters like drainage density, stream length index and bifurcation ratio values. The study unfolds the ground condition to perform major civil projects and hazard preventive measures up to catchment level.

In the Chenab River Basin, the mature landform is represented by moderate slopes, wide valleys, meandering rivers and river terraces, whereas the young landforms consist of steep slopes and narrow valleys with straight river courses. The evaluation of morphometric parameters imposes the analysis of various drainage parameters [1] according to the pattern of length, area and elevation components [2].  In the study area, the geomorphology mainly depends on the lithology and structure of the underlying rock formations. The control of lithology on the development of landforms is seen over the metamorphic rocks which are dominant in the study area and are more resistant to erosion but weathering is highly active where joints have developed. The major landforms observed are of structural, glacial, fluvial and denudational type. In the upper reaches of the area, characteristic sharp-crested peaks and broad u-shape valleys are present that indicates the glacial erosion of the surface. The mountain building activities, in the geological past, deposited talus and fluvial glacial material at the angle of repose and in such places weathering are high.

The quantitative analysis of morphometric parameters calculated in this research provides information regarding overall erosion and tectonic activity in the Chenab River Basin. All the morphometric parameters (topographic, relief, areal, linear and network parameters) have been calculated for the 32 sub-basins, except Vf, SL (calculated for three major sub-basins of the study area, i.e., Chandra, Bhaga and Chenab, fig. 1) and Af (calculated for Chenab River Basin). The result of relief and topographic parameters shows that the central part of the study area is topographically complex, which is most likely a result of the varied lithology and presence of geological structures. The Rc and Re were calculated according to Miller’s Method (1953) and discussed according to Strahler [3], Schumm [4] and Panhalkar et al. [5]. This fragile geological setting is a major indicator for the presence of landslides in the study area, which is further counter checked during field expeditions. The drainage pattern and density related parameters depicted that the target area has inhomogeneity in texture and control of geological structures over it. Drainage frequency shows the northern portion of the study area has low infiltration and absorption rate; thus, it will act as a safe source of surface runoff or inflow for the Chenab River.