Quantitative Analysis of Geomorphology and Flow Pattern Analysis of Muvattupuzha River Basin Using Geographic Information System

Abstract

Morphometry and terrain analyses are important in geomorphology where quantitative measurements are made on physical characteristics of landforms. It is done mainly to understand the structure, processes and evolution of landscape. Analysis of the flow pattern in the basin helps to relate the runoff characteristics to the morphometric parameters. In this paper, an attempt is made to study the morphometric aspects of streams and terrain characteristics of landforms of Muvattupuzha river basin of Kerala along with its flow pattern analysis. Geographic Information System was used for generating vector maps of the boundary and drainage. SOI topographic maps of scale 1:50000 were used for extracting the vector maps using GIS software like MapInfo and ArcGIS. The Kaliyar River, Thodupuzhaaar and Kothamangalamaar joining together at Muvattupuzha and flowing down the south-west as a single river for about 115km after confluence and traversing a total length of 121km constitutes the Muvattupuzha river basin. The total drainage area of the river is 1554 km2. The Muvattupuzha river basin was sub divided into five sub-basins for analysis, namely Malankara, Kalampur, Kakkadassery, Thodupuzha and Muvattupuzha. The linear, areal and relief aspects were studied and related to the mean discharge and peak runoff of the basin and its sub-basins. The linear aspects of morphometry such as stream order, stream length, stream length ratio and bifurcation ratio and areal aspects like drainage density, stream frequency, form factor, elongation ratio, circularity ratio, length of overland flow were calculated for the river basin. The Muvattupuzha basin was found to be a sixth order basin with a mean bifurcation ratio of 4.6. The basin has an average drainage density of 1.34kms/km2. Since stream frequency depends on the drainage network, it also has a low value of 1.34/km2.The pattern of drainage was identified as dendritic showing that the drainage basin is composed of fairly homogeneous rock. The elongation ratio of Muvattupuzha basin was found to be 0.69 indicating that the terrain is elongated in shape. The length of overland flow of the basin is 0.81 representing a gentle slope of terrain with long flow path. The results show that the laws formulated by Horton with reference to quantitative geomorphology are applicable to most of the sub-basins of the Muvattupuzha river basin, situated in the highland and midland. However the law doesn’t hold good for lowland or coastal belt. This could be because of non-homogenous nature of bed rock. The longitudinal profile of the river basin which was developed using altitude and distance from river mouth clearly represents the morphometric parameters derived. Significant regressions were established for mean discharge and peak runoff on stream length, relief ratio, elongation ratio and area, but not circularity ratio. These relationships can be used to estimate stream flow at ungauged portions of the drainage basins. However, the applicability depends on uniformity in rainfall pattern, lithology, soil type and land use pattern of the basin considered.