River Floods and their management

River Floods and their management

  • The vast stretch of alluvial plains from Maharajganj in eastern Uttar Pradesh to Karimganj in Assam’s Barak Valley has been frequently affected by multiple water hazards. This is a densely populated area stretching across Uttar Pradesh, Bihar, West Bengal, and Assam. These four states account for 17% of India’s geographical area, but disproportionately account for 43%–52% of all flood-prone areas of the country.
  • Although the recurrent floods are a natural phenomenon, they are also an outcome of anthropocentric interventions. It is natural that the high precipitation in the Himalayas—the catchment of most of the tributaries of the Ganga and Brahmaputra—coupled with the sudden fall in altitude results in a large volume of water gushing down river channels from the Eastern Himalayas into the floodplains. This water exceeds the carrying capacity of the river channels resulting in a spillover into adjoining areas.
  • With increased deforestation in the Eastern Himalayas, the surface run-off has increased at the cost of infiltration leading to tons of sediment being deposited on the riverbed as the river reaches the plains. This further reduces the carrying capacity of the river and enhances the risk of flooding. The plan to build large dams in upstream areas, largely in Arunachal Pradesh, is likely to exacerbate this process.

Issue with embankments:

Historically, embankments have been the gold standard for flood protection but there are various issue associated with them-

  • Embankments were constructed to create a “safe” area for habitation and they provide these in areas where the embankments are new. But in areas like North Bihar and Assam, where there has been a fairly long history of embankments, the situation is complicated. Large populations continue to stay inside the embankment, that is, outside the “safe” areas, at the mercy of the imminent flood.
  • Unfortunately, people located in the “safe” area also live in constant fear of embankment breach. Their fear is not completely unfounded—the floods in Assam this year and the Kosi River flood of 2008 were outcomes of embankment breach.
  • Furthermore, people living inside the embankment face the risk of flash floods. The latter is due to a gradual increase in water level, while the former, as was seen in Uttarakhand in 2013, occurs when there is sudden high discharge from a reservoir into the river channel.

Understanding floods in better way:

A shift is required in the understanding of floods from being an extreme weather event, to a hazard that is partly natural and partly anthropogenic.

  • Flooding is natural because the rivers in the Northeast, mostly originating in the Eastern Himalayas, experience a sharp fall in gradient as they move from Arunachal Pradesh and Bhutan to reach Assam’s floodplains. This fall in altitude causes a large volume of water to gush to the floodplains.
  • Most of these rivers carry large amounts of sediments, which then get deposited on the floodplains, reducing the storage capacity of the river channels and resulting in inundation of the adjoining floodplains. Flooding is partly anthropogenic as the sediment load carried by the rivers is accentuated through “developmental” interventions in the Eastern Himalayas that result in deforestation.

Issues with present strategy of flood protection:

The dominant narrative of flood protection includes measures such as embankments, dredging rivers and bank strengthening.
In a study spread over 96 villages in Assam, Bihar, UP, and Bengal, we found embankments are cost-intensive options. The focus here has been more on construction and less on maintenance.
The scope of storage dams in Arunachal Pradesh is limited, given the region’s geology and the ecology. Proposals for dams have been a matter of serious debate in Assam and Arunachal Pradesh.

Flood Governance: Building resilience

There is a need to shift the focus of action towards flood affected people. This will require building resilience of these communities.

  • Access to schools during the flood months is restricted, because the schools are either inundated or are make-shift relief centres.
  • Water and sanitation issues require attention during the flood months.
  • Floods are accompanied by outbreaks of diseases such as diarrhea. Access to veterinary services is limited resulting in high cattle mortality and morbidity.
  • People in the flood-prone areas in the Northeast, by and large, practice subsistence agriculture. While the land remains inundated for an extended period in the monsoons, limited irrigation coverage (less than 10 per cent in Assam, compared to 49 per cent as an average for the country) constrains intensification of agriculture in the dry months.

Flood governance: Bringing sustainable changes

Flood governance through resilience building could bring about sustainable change in the situation. This could be an outcome of three broad sets of action:

  • Reducing vulnerability-
    Community-based advance flood warning systems, for example, have been successfully piloted in parts of Assam. Providing adequate number of boats — the most important, yet scarce resource in the villages — will enhance access to developmental activities during floods and also facilitate safe commute for schoolchildren.
  • Increasing access to services-
    Usual toilets are of limited use in flood-prone areas. Elevated toilets, ecosanitation units — promoted in the flood-prone areas of North Bihar — and elevated dugwells or tubewells with iron filter need to be installed in the Northeast. These are more expensive than the Swachh Bharat toilets and wells or handpumps. But if promoted on a large-scale, they will reduce the public health challenges in the flood-prone areas.
  • Maximising productivity through optimal use of available resources-
    Productivity can be maximised by giving people access to cheaper sources of irrigation, research on short duration boro paddy, and innovative agriculture techniques like floating vegetable gardens. Scientific fish farming on the waterbodies and the inundated land can ensure that inundation, when it cannot be avoided, is put to optimal use.

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