Floods and coastal inundation issues

ACCCRN India: Synthesis Report – Volume I 43

4.5.1 Floods and coastal inundation issues

The expansion of the city from comparatively safe old core to possibly higher risk periphery as well as disrupting and constraining natural drainage by expanding in to both sides of the river lood plain can only increase the lood and coastal inundation risks. In costly real estate environment, the risks get ignored and haphazard growth by multiple real estate developers only complicates the risk situation. The integrated risk informed master planning process is yet to take root in urban planning debate. Indian urban land is quite costly due to limited availability of land in the core areas, poor transportation network and archaic land use single use and building rules that discourage compact growth. Haphazard growth of the periphery and inability to extend the lifeline services, further distort the land markets. With the Para-statal Urban Development Authorities developing partial infrastructure and handing over these areas to ULBs further stress the inances and technical capacity of the ULBs to integrate resilience in urban planning. The National Disaster management Authority has recognized following reasons for growing urban lood risks NDMA 2010: ƒ Increase in impermeable areas and resultant higher runoffs ƒ Lower design criteria of storm water drains ƒ Capacity reduction of storm water systems due to lack of maintenance, ƒ Encroachment of natural drainage areas ƒ Reservoir management issues ƒ Poor solid waste management and ƒ Dumping of construction wastes on drainage lines and illing of natural water bodies. ƒ Absence of sewerage and dumping of sewage in to drainage system. ƒ Urban micro climate as well as global climate change aspects of increasing looding frequency. The above list captures combined impacts of urbanisation and climate change on urban looding. The Guidelines suggest various measures to manage urban loods including early warning systems, better designs of drainage systems. It has to be noted that NSHM has accepted the recommendations of International Conference on Urban Drainage in 2008, to 20 increase in calculated discharge suggested for designing for future storm water drains NSHM undated.

4.5.2 Temperature increase, urban heat island effects and energy use: