Urban Flood Model for Bangalore City

Bangalore, capital city of Karnataka is the sixth largest metropolis in the country and a nerve center for the various cultural, social and religious activities, contributing to the growth of the city. Bangalore district is situated in the heart of the South-Deccan plateau in peninsular India to the South-Eastern corner of Karnataka State between the latitudinal parallels of 12°39' N & 13°18' N and longitudinal meridians of 77°22' E & 77°52'E at an altitude of about 3000 ft. above sea level covering an area of approximately 800 sq. kms. The temperature varies from a minimum of 14°C to a maximum of 33°C and Rainfall (Actual) of about 1060 mm. The pleasant weather has the warmest months from March to May, coldest months from December to January, rainy - southwest monsoon from June to September and rainy - northeast monsoon from November to December.

Bangalore has a total of 198 wards spread across the 4 taluks namely, Bangalore North, Bangalore South, Bangalore East and Anekal. It is also categorised into zones namely, Byatarayanapura Zone,Dasarahalli Zone, Rajarajeshwarinagar Zone, South Core Zone, West Core Zone, East Core Zone, Bommanahalli Zone and Mahadevapura Zone.

Storm Water Scenario

The city’s topography is characterized by a series of well-defined valleys which radiate from a ridge at a location called high ground to the north of the city and fall gradually in all directions. The three zones in core area are further demarcated by natural topography into four major watershed catchment area namely Vrishabhavathi valley catchment, Koramangala valley catchment, Challghatta valley and Hebbal valley catchment .Three of the valleys Vrishbhavathi valley, Koramangala valley and Vrishabhavathi valley ,run in north to south direction and divide the greater part of the area which lies to the south of the ridge into three separate and distinct drainage zones. A fourth major valley, referred to as the Hebbal valley forms the drainage zone of the north of the ridge and runs in the northern direction.

Need for Storm water Management in Bangalore

Considering the rainfall data from 2009 to 2014 the trend shows an increase in the rainfall intensities. The rapid urbanization and land changes have led to increased rainfall intensities. The recent rains in Bangalore have flooded the city leading to deaths and damages. All these force the necessary of upgrading the drainage infrastructure of the city in order to protect it from Flood risks.

Urban Flood Management

Urban Flood management needs a multi-disciplinary holistic approach, Scientific and technological methods for monitoring, and decision making. It is not the responsibility of only the City Corporation, but integration between the multiple organizations to manage the Storm water in Bangalore city Area.

The highest flood prone areas have been identified in the east zone which compromises mainly the central business district and other parts, mostly occupied by government officials and politicians. East zone has 48 flood prone areas; south zone has 30, Rajrajeshwainagar and Mahadevapura zones have 25 each; west zone has 22; Bommanhalli has 14; Dasarahalli and Yelahanaka zones have 5 each respectively.

Importance of LIDaR Survey

LiDAR (Light Detection and Ranging) is a remote sensing method that uses light in the form of a pulsed laser to measure terrain elevation at finer spatial resolution typically 10-20 cm. Such fine resolution data will be able to capture the near real ground conditions and the corresponding land uses. In urban scenario density of population is more as compared to rural areas, in this case, coarser resolution data may underestimate the flood quantities, which eventually leads to catastrophic damage to human life. This condition necessitates the incorporation of fine resolution data such as LiDAR data in the development of flood forecast and management model for the densely populated city like Bangalore.