Flood susceptibility analysis in Chennai Corporation using Frequency Ratio Model
Résumé
Natural disasters like flood are causing massive damages to natural and human resources, especially in coastal areas. In
respect to social, economic and environmental perspective, flood is one of the most devastating disasters in Chennai for the
recent days. Flood susceptibility mapping using frequency ratio model was done for the 88 micro watersheds of Adyar,
Cooum and Kosasthalaiyar watersheds of Chennai Corporation area. Flood Susceptibility map was generated using
frequency ratio model by considering ten different independent variables (landuse/land cover, elevation, slope, topographic
wetness index, surface runoff, landform, lithology, distance from the main river, soil texture and soil drainage) through
weighted-based bivariate probability values. In total, 123 historic flood reported locations were taken for this study from
which 100 locations were used for susceptibility mapping and 23 locations were used for validation. Both the independent
variables and historic flood locations were combined together to generate frequency ratio database for flood susceptibility
mapping. The developed frequency ratio was varied from 0 to 27.11 and reclassified into five flood vulnerability zones
namely, very low (less than 5.0), low (5.0 7.5), moderate (7.5–10.0), high (10.0–12.5) and very high susceptibility (more
than 12.5). The result revealed that 10.48 and 38.93 percentage of the land have very high and high vulnerable class,
respectively. The frequency ratio model validated using 23 flood locations, where 22 locations are presented in high and
very high susceptibility class. This analysis exemplified that prediction was with success rate of 95.6%. The flood
susceptibility analysis using this model will be very useful and efficient tool to the local government administrators,
researchers and planners for devising flood mitigation plans.