Flood

Floods

Flooding occurs when water levels along rivers or along the shore rise to such an extent that it submerges normally dry land. While flooding is a natural part of the hydrological cycle of drainage basins, it becomes a disaster when excessive rainfall leads to conditions where it results in loss of life, property, and infrastructure.

Floods are typically caused by a combination of meteorological and physical factors, which may be worsened by human activities.

Causes of Floods

Floods can be triggered by several meteorological and physical factors:

Meteorological Causes:

1. Heavy and Continuous Rainfall: Flooding can occur when prolonged, intense rainfall surpasses the region’s drainage capacity. In India, areas with over 100 cm of rainfall are particularly vulnerable.
2. Cloudbursts: A cloudburst occurs when an unusually high volume of rain falls in a very short time. This is particularly common in the Himalayan region, Odisha, and parts of Western India.
3. Tropical Storms and Cyclones: Tropical storms originating from the Bay of Bengal and the Arabian Sea are frequent causes of flooding in India’s coastal areas, particularly Andhra Pradesh, Odisha, and Gujarat.

Physical Causes:

1. Large Catchment Areas: Rivers with vast catchment areas, such as the Ganga and Godavari, collect a significant volume of water, making these regions prone to floods.
2. Obstructions in River Flow: Landslides, sediment buildup, and river meandering can block the natural flow of water, causing water to accumulate behind the obstruction. Eventually, the “dam” formed by these obstacles may break, causing a flash flood downstream.

Human Causes:

1. Deforestation: Deforestation leads to the loss of plant roots that would typically absorb rainwater, causing more surface water runoff and contributing to flooding.
2. Poor Agricultural Practices: Incorrect ploughing techniques can allow water to flow unchecked along the slope of the land, leading to floods in lower-lying areas.
3. Irrigation and Water Management Failures: Poor irrigation techniques, such as in Punjab and Haryana, can lead to waterlogging. This reduces the soil’s ability to absorb water, making even minor rainfall lead to floods.
4. Rapid Urbanization: Urbanization obstructs natural water flow, as cities typically build on floodplains or drainages. The increasing amount of waste and sewage dumped into rivers can decrease their water-carrying capacity, further exacerbating flooding.

Effects of Floods

Floods have a variety of adverse impacts, especially as their frequency, intensity, and magnitude are increasing over time due to factors like environmental degradation (such as deforestation). The most serious effects of floods include:

1. Loss of Life and Property: The most direct impact is the loss of human lives and significant property damage.
2. Economic and Social Disruption: Floods can cause destruction to infrastructure, disrupt economic activities, and lead to the displacement of people.
3. Agricultural Damage: Floodwaters destroy crops, leading to food shortages and economic losses, particularly in agriculture-dependent areas.
4. Health Impacts: Flooding leads to poor sanitation and hygiene, spreading diseases like cholera and dysentery. The displacement of people and contamination of water sources further exacerbates the situation.
5. Environmental Damage: Floods wash away soil and vegetation, disrupt ecosystems, and cause long-term environmental degradation.

Floods disproportionately affect vulnerable populations, especially those living in poor or marginal areas who cannot afford to rebuild or relocate after a disaster.

Flood-Prone Areas in India

India is particularly vulnerable to flooding, with several regions being identified as flood-prone:

• North Bihar, Uttar Pradesh, and West Bengal: These areas, located along the Ganga and Brahmaputra river systems, are prone to severe flooding due to heavy rains and the large catchment areas of these rivers.
• Coastal Regions: Areas along the coasts of Andhra Pradesh, Odisha, Gujarat, and more recently Kerala and Tamil Nadu, are also vulnerable.
• Himalayan Region: States like Jammu & Kashmir and Uttarakhand have witnessed devastating floods, including the 2014 floods in Kashmir and the 2013 floods in Uttarakhand caused by cloudbursts.

Urban Flooding

Urban flooding occurs when heavy rainfall overwhelms the drainage systems in developed urban environments. Urban areas are particularly susceptible to flooding because the built environment increases runoff, reduces the soil’s ability to absorb water, and often has inadequate infrastructure to manage extreme rainfall events.

Impacts of Urban Flooding:

• Loss of Life and Property: The immediate and most tragic impact of urban flooding is the loss of lives and destruction of property.
• Infrastructural Damage: Severe flooding can damage essential services, including water supply, sewage systems, power lines, and transportation networks.
• Public Health Crisis: The spread of waterborne diseases is common during urban floods due to the contamination of drinking water supplies and exposure to untreated sewage.
• Environmental Damage: Vegetation and ecosystems within urban areas are often damaged or destroyed by extreme flooding, further harming biodiversity.

Urban flooding is becoming increasingly frequent and severe, partly due to rapid urbanization, the inadequate planning of drainage systems, and climate change. As cities expand, their vulnerability to flooding grows, particularly in regions that were not initially designed to handle such extreme weather events.

Flood Disaster Management

Flood disaster management involves strategies to prevent the rapid and overwhelming flow of excess water through the drainage network. The primary objective is to manage and control floods using both structural and non-structural measures. Structural measures include the construction of reservoirs, embankments, channel improvements, town protection works, and river training, all aimed at controlling the flow and reducing the damage caused by floods. The key steps in managing flood disasters include:

1. Flood Forecasting: Anticipating the onset of floods through advanced meteorological and hydrological analysis.
2. Reduction of Runoff: Implementing techniques to limit the amount of rainwater flowing into the drainage system, which can help reduce flood risk.
3. Reduction of Flood Peaks by Volume Reduction: This involves the construction of dams, detention basins, and other infrastructure to store excess water, thereby reducing the intensity of floods.
4. Reducing Flood Levels: Lowering the height of floodwaters through controlled drainage and management of water flow.
5. Protection Against Inundation: Building embankments and levees to prevent floodwaters from entering urban or agricultural areas.
6. Flood Plain Zoning (FPZ): Designating areas that are most susceptible to flooding and restricting development or settlement in these zones to minimize the risk.

Flood Control Programmes and Policies

Government’s Initiatives and Policies on Floods

The National Water Policy of India has undergone several revisions (1987, 2002, and 2012), each focusing on improving flood control and management.

1. National Water Policy (1987): This policy emphasized the need to provide sufficient flood cushion in water storage projects to better manage floods. It highlighted the importance of integrating structural flood protection measures with non-structural methods like flood forecasting, warnings, and flood plain zoning.
   
2. National Water Policy (2002): This version built on the previous policy, urging the preparation of a master plan for flood control and recommending a balance between physical flood protection works and non-structural strategies. It also stressed regulating settlements and economic activities in flood-prone areas to minimize damage.
   

National Water Policy (2012): The 2012 policy reiterated similar principles, with a focus on sustainable flood management and coastal land management plans, particularly for coastal states.