Abstract
The present study attempts to understand the form and geomorphic/hydrologic processes of the 20 watersheds of the Pachamalai hills and its adjoinings located in Tamil Nadu State of southern India from the analysis of its drainage morphometric characteristics. Survey of India’s topographic sheets of 1:50,000 is the data source from which stream networks and watersheds of the study area were demarcated followed by the analysis of their morphometric characteristics using ArcGIS software. The results of the analysis formed the basis for deducing the form and processes of the watersheds of the study area. The form of the watersheds inferred from the analysis includes shape, length, slope steepness and length, degree of branching of streams, dissection and elongation of watersheds. The geomorphic/hydrologic processes inferred include denudation rate, potential energy, intensity of erosion, mean annual run off, mean discharge, discharge rate, rock resistivity and infiltration potential, amount of sediment transported, mean annual rainfall, rainfall intensity, lagtime, flash flood potential, flood discharge per unit area, sediment yield and speed of the water flow in the streams. The understanding of variations of form and processes mentioned can be used towards prioritizing the watersheds for development, management and conservation planning.
Highlights
Drainage basin or a watershed refers to the entire area providing runoff to and sustaining part or all of the streamflow of, the main stream and its tributaries
In recent times especially since the last decade, the advancements made in Remote Sensing and Geographical Information System (GIS) technology has taken the study to the level
ArcGIS software was utilized to calculate measures such as number of streams, length of streams, area and length of watersheds, and elevation ranges and were made use to estimate a number of parameters relating to linear, areal and relief aspects in each of the watersheds of the study area
Summary
Drainage basin or a watershed refers to the entire area providing runoff to and sustaining part or all of the streamflow of, the main stream and its tributaries. Quantitative analysis of drainage network within a basin or watershed can throw light upon the form and predominant processes in them, a knowledge which is indispensible for planning relating to watershed management, floods, soil erosion, mass movement, neotectonic activities, surface and groundwater, derivation of hydrographs and understanding discharge characteristics of ungauged stream, ecology, etc. The description of drainage network within a basin which was purely qualitative was transferred into a rigorous quantitative science capable of providing numerical data of practical value by Horton (1932, 1945). A number of related studies have been carried out since for which topographic maps and data obtained from field work have been the source. An attempt has been made to understand the form and processes of the watersheds of the Pachamalai hills and its adjoinings located in the central Tamil Nadu State of southern India. The rain water that flows through these streams is the major source of water flow for the important rivers that flow through the adjoining foot hills and plains of the region such as Swetha Nadhi,
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