DYE-TRACING METHODOLOGY FOR SOIL INFILTRATION ESTIMATION IN GUWAHATI CITY

Abstract

Soil hydrologic condition is the result of interplay between soil and vegetation which to a great extent govern the infiltration capacity of the soil and hence generation of runoff. Rapid urbanization has significantly increased the risk of flash floods particularly in steep, hilly terrains of Guwahati city especially during high intensity - short duration rainfall events causing large-scale devastations to life and infrastructure. The objective of this paper is to estimate the soil infiltration depth and hydrophobicity useful for hydrological modeling of flash floods.  The results illustrated that vegetative classes like bamboo, forests, plantation or shrubs favour deep infiltration through preferential pathways in the soils. However, homestead or residential areas have showed lesser depth of infiltration due to compressed and impervious areas.  Vegetative classes like forest, plantation, bamboo and shrub classes have showed lesser hydrophobicity than homestead and residential classes. Therefore, Plantation and afforestation on the hills can also help reduce flash floods considerably in Guwahat city. Application of vetiver grass could also effectively detain runoff by conducting runoff to deeper subsurface as they have long, bushy root structure. Therefore dye-tracing is an effective methodology to measure infiltration depths under different landuse classes.