Flood-proof Himalayas

The Indian Himalayas grappled with cataclysmic floods this August. Unrelenting downpours propelled by an erratic climate pushed many towns in Himachal Pradesh into a maelstrom of inundation. News reports suggest that the state alone lost more than 150 human lives and incurred damages spiralling to an estimated US $120 million.

Similar destruction has been reported by several towns across the Hindu Kush Himalaya (HKH), which is spread over eight countries. In 2023, a rainless July was followed by destructive floods in August in Bangladesh’s low-lying district of Bandarban in the Chittagong Hill Tracts. The floods submerged approximately 80 per cent of Bandarban’s municipal expanse under 4.5-6 m of water. The flood’s primary catalyst was an extraordinary 268 mm of rain within 24 hours. The unplanned construction on the riverbank aggravated the disaster by reducing river navigability and obstructing water flow. The resultant catastrophe underscores a sobering reality: the simultaneous affliction of diminished river capacity and a compromised drainage system, culminating in an inefficient channelling of excess water.

For HKH cities to become resilient, it is crucial for local governments to enforce strict town planning, with the use of spatial land-use planning approaches and associated information technologies for climate change adaptation.

Though floods happen regularly in areas of lower elevation, they are far from merely natural. Rapid urbanisation bulldozed the natural floodplains, making way for unchecked construction along riverbanks and recognised flood risk zones. This encroachment compromised natural flood zones, turning them into conduits for disaster. Construction debris and loose soil are dropped into rivers, impeding the flow. Additionally, discarded plastic waste compounds floods by obstructing waterways. Alteration of traditional farming practices, soil degradation and sedimentation worsened the crisis, impeding the land’s ability to absorb rainfall. When intense monsoon downpours surged beyond drainage capacities, the inevitable outcome was rivers bursting their banks, inundating everything in their wake.

Need for spatial data

A critical feature of the towns and settlements that bear the brunt of these crises is that they have largely overlooked the power of participatory technology-based spatial land-use planning. A lack of climate risk consideration has granted unbridled freedom to erect residences with little restraint. However, spatial land-use planning holds the key to multifaceted benefits—mitigation against floods, landslides, and climate change, while bolstering environmental quality. This approach engages communities and authorities in a concerted effort, employing consensus-based decision-making to designate risk-prone zones as restricted areas.

Strategic infrastructure placement minimises susceptibility to disasters. A land use zone and priority determination process can guide settlement placements away from flood-prone zones. To succeed, such planning must be attuned to specific challenges—such as lost drainage functions in mountainous terrain and increasing water scarcity. In addition, established flood shelters through suitability mapping can mitigate the disaster risk.

In this digital age, information technologies emerge as crucial assets. Geographic Information Systems (GIS) and Earth Observation (EO) data streamline spatial planning, harmonising natural resource management. By integrating diverse EO images and spatial data, GIS evaluates the dynamic changes in land use, projects future scenarios and conducts risk assessments by mapping flood hazards, exposure, and vulnerability. During floods, real-time flood inundation data is a lifeline for disaster response and relief, enabling timely action and reducing casualties. Satellite-based EO techniques generate flood maps and assess damage to properties, infrastructure, and crops, facilitating early warnings and swift disaster management.

Before a flood, community-based flood early warning systems can reduce casualties by transmitting flash flood alerts. The International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, Nepal, has developed a low-cost grassroots community-based flood early warning system that empowers local communities to safeguard their lives and livelihoods from the effects of floods.

Besides technological interve-ntions, simply planting native trees and having retention ponds are potent allies in the Himalayan region’s battle against flash floods and climate vulnerability. Embracing nature-based solutions—a broad range of actions inspired and supported by nature—can help address challenges people are facing as a result of climate change, biodiversity loss and environmental degradation. Planting native trees along riverbanks and beside residential areas can create natural barriers that slow floodwaters. These lush canopies absorb excess rain-water and can help recharge natural springs.

Currently, we only worry about floods once they have already hit us. What is needed is to prepare for them beforehand through climate-resilient activities. By ensuring participatory spatial planning approaches and nature-based solutions, HKH forges a resilient front against floods, uniting communities and policymakers for safer coexistence and heightened climate resilience in the HKH region.

Kabir Uddin is a GIS and remote sensing specialist and Gillian Summers is senior editor at the International Centre for Integrated Mountain Development or ICIMOD in Kathmandu, Nepal

This was first published in the 1-15 September, 2023 print edition of Down To Earth

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