Study on the Impact of Land Use Changes on Urban Hydrology of Cochin, Kerala, India

Abstract

Urbanization and population pressure are the two main challenges for water resource management, especially in cities of developing countries. The process of urbanization results in land use alterations. Urban development can have a major impact on the local hydrology. The growth of urban areas results in significant changes in the physical properties of the land surface consequently increasing impervious surface area. Imperviousness is the most critical indicator to analyze the impact of urbanization on the hydrology. As a direct consequence, this results in increased surface runoff. Indirectly, this results in a reduction in infiltration, eventually altering the prevailing hydrologic system. The present study is an attempt to quantify the impact of land use changes due to urbanization on surface and subsurface hydrology. The study area is Cochin, one of the fast developing second tier metros in India. We estimated the runoff volume and ground water fluctuations for the study area. SCS-CN method was used to calculate runoff volume. The land use changes for the study area were prepared from Survey of India topographic map as well as satellite data. Runoff depth and volume was calculated for various land use categories using daily rainfall data for the past three decades. We also calculated the depth to ground water table for dug wells for last three decades in the study area. Depth to ground water table measured was used to generate water table contours using triangulation method. The water table contours were classified into four and the area under each class was measured since 1980. It was found that, the area for shallow water table gets decreased for the past three decades clearly depicting an increasing depth trend.