Q3A · Discuss in detail the three key causes that resulted in Mumbai Floods 2005. Also sugg…

Answer

1. Event and setting: Extreme rainfall on 26 July 2005 caused severe flooding in Mumbai and surrounding areas.
2. Causes and vulnerability: Intense rainfall interacted with inadequate or obstructed drainage, loss of natural storage, low-lying development and tide-related drainage constraints.
3. Impacts: Transport paralysis, deaths and injuries, housing damage, disrupted livelihoods and public-health risks.
4. Response and recovery: Rescue and shelter, restoration of services and attention to drainage, warning and urban-planning weaknesses.
5. Lessons: Maintain drains; protect wetlands and natural flow paths; plan outfalls and detention; issue local warnings; regulate exposed development.

Three interacting causes

1. Exceptional rainfall. A very large rainfall input rapidly produced runoff.
2. Restricted conveyance. Blocked or inadequate drainage and constrained river/outfall flow limited removal of water.
3. Exposed urban development. Impervious surfaces, loss of storage and low-lying development increased runoff and the people and assets affected.

Four mitigation measures

1. Maintain the catchment and natural storage. Protect wetlands and floodplains and restore suitable vegetation. These measures slow runoff and store part of the floodwater, although they cannot eliminate extreme floods.
2. Manage channels and drainage. Remove blockages and maintain bridges, culverts and drains. Engineering surveys should guide selective desilting; indiscriminate excavation can damage banks and ecosystems.
3. Use storage and coordinated reservoir operation. Detention basins and reservoirs can hold water and release it more slowly. Forecasts, operating rules and downstream warnings are essential because storage and outlet capacity are finite.
4. Apply floodplain zoning and resilient construction. Keep new critical facilities outside high-risk zones. Where occupation is permitted, use suitable raised floors, protected utilities and evacuation access to reduce losses.