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Mains Test Series

Soil and Natural Hazards

Q. Both causes and consequences of the urban and rural floods are different. Discuss. (150 words)

Introduction:

A flood is overflowing the usual confines of a stream or other body of water or accumulating water over areas that are not usually submerged. Floods are not exclusive to rain. Tsunamis and failed water management systems can also cause floods.

According to the National Disaster Management Authority, out of India’s 329 million hectares of geographical area, more than 40 MHa are flood-prone.

Causes of Urban Floods:

  1. Unplanned development: The rapid development and consequent infrastructure, such as road building, fail to account for the natural drainage systems without providing cross-drainage works.
  2. Encroachment: Most of these infrastructural development projects in lowlying areas of Indian cities take place on encroachments over lakes, wetlands, and riverbeds, reducing the water-carrying capacities of water bodies.
  3. Inadequate Drainage Facilities: In urban areas, there are fewer drains, the ground is highly compacted, and pathways between dwellings become streams after heavy rain. The built environment, like cities, generates higher surface runoff, which is more than drainage capacity, thereby causing floods.
  4. Release of water from dams: Sudden and unplanned release of water from dams and lakes without giving the public enough time to respond. Dam failure sends a sudden destructive surge of water downstream.
  5. Increased imperviousness leads to increased runoff compared to drainage capacity, improper waste disposal resulting in clogged drains, high intensity and high runoff load.

Causes of rural floods:

  1. Breach of Natural embankments or levees: This is, for example, often seen in the case of Koshi River, Bihar.
  2. Poor dam management: For example, in the 2018 Kerala flood, poor dam management led to overcapacity in the reservoirs and forced the managers to release water, leading to floods.
  3. Excessive rainfall causes river overflow, which leads to. In coastal areas, excessive rainfall might be accompanied by storm surges.
  4. Riverbank erosion: Flood water can alter the landscape, for example, by eroding riverbanks and causing them to collapse and flooding nearby areas. Impact of floods:

Effects of urban floods:

  1. Structural damage: It damages houses, often roofs of semi-permanent dwellings and Kutchha houses collapse. The prolonged contact with the water leads to erosion of the soil present in the ground.
  2. Disrupts infrastructure, like the water supply, sewerage, power lines, transmission lines, communication and traffic on roads and railways.
  3. Health problems, including epidemics and plagues, dengue, and malaria, are caused by stagnant stormwater, contaminated drinking water and solid waste sewage.
  4. Hazardous chemicals may be spread by flood water from damaged production facilities or storage areas. Untreated sewage and toxic chemicals can significantly threaten public health and water supply.

Effects of rural floods:

  1. Loss of biodiversity and wildlife: Farming and ranching habitats are also susceptible to the flood water that inundates their living areas and causes loss of biodiversity and wildlife in the affected region.
  2. Agricultural loss: Flash floods may cause massive crop and vegetation losses.
  3. Loss of Animals: Floods can adversely affect the well-being of the animals and plants housed in forest areas.
  4. Health problems: The immediate effects of floods include drowning, hypothermia, and animal bites. Health risks include loss of health infrastructure, including essential drugs and supplies.
  5. Chemical contamination: Agricultural chemicals, including fertilizers and pesticides, as well as other pollutants such as paint, gasoline or diesel, can find their way into wildlife habitats.

Positive impact in case of rural floods:

  1. Brings nutrients: Floodwater brings nutrients and essential components for life and renewing the ecosystem.
  2. Recharge underground water: Floodwater gets percolated through layers of soil and rock, reaching underground aquifers.

Way forward:  

  1. The Sendai framework: adopting measures that address the three dimensions of disaster risk, i.e., reduction of vulnerability and capacity building and increased resilience.
  2. In building a sponge city, a nature-based solution in which the landscape retains rainwater in urban areas.
  3. Building sustainable and resilient infrastructure.

Conclusion:

The development of blue-green infrastructure will help in the situation, and for better development planning, geospatial technology should be used for flood vulnerability mapping, and natural water bodies should be strictly designed and maintained to ensure the free flow of excess water.

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