How Do We Stop These Devastating Floods? Start With These Six Steps

Floods are becoming more devastating in parts of Asia due to climate change. Photo: ADB
Floods are becoming more devastating in parts of Asia due to climate change. Photo: ADB

By Rabindra P. Osti

The devastating floods in the Hindu Kush Himalaya Region have shown the urgency of actions needed to protect vulnerable communities from the impact of climate change.

The Hindu Kush Himalaya Region is facing flash floods that are becoming one of the most devastating disasters in recent years. By some estimates, more than 50 million people have been affected.

In this region, which stretches over parts of Afghanistan, Bangladesh, Bhutan, the People’s Republic of China, India, Nepal, Myanmar, and Pakistan, flash floods are often triggered by intense rainfall in small watersheds, accelerated glacier melting, glacial lake outbursts, and breaches of dams. People living in the foothills of mountains are particularly vulnerable.

Why is this happening? People in this area are living on "alluvial fans”, which are areas in foothills formed over time by sediment deposit from rivers. Historically, particularly in relatively stable geological and climatic conditions, these alluvial fans were relatively firm and fit for human settlement.

Unfortunately, these areas are no longer stable because of changes to mountain rivers caused by climate change and land use. Unsustainable land use practices include rapid development on mountain slopes, deforestation, loss of flood retention areas including wetlands, and slope farming.

  Unjustified and illegal rock mining from the rivers to meet an increased demand for construction material has further destabilized the rivers. As a result, intense rainfall can generate massive mudflows or debris flows. Debris flows are very powerful. They wash out almost everything in their path, as seen in many recent flood disasters.

Illegal and unscientific sand mining, as well as river dredging, has caused erosion and sand depositing as rivers adjust to these changes. This movement of sand contributes to the destruction of structures along the river bank such as bridges, as documented in recent floods.

These changes force rivers to find their equilibrium, which often involves them changing course and reshaping the alluvial fans where they deposit sediment. These changes can make rivers very unpredictable and violent in downstream reaches. In a sense, it can be said that these destructive human activities puzzle the rivers, which then have to make natural changes to adjust.

There is no catch-all solution to the flooding in the region. Problems are unique at each location.  Successful flood hazard management requires strong and long-term political, technical, and financial commitments, supported by comprehensive assessments. Hazard management is just a part of the solution.

Pakistan is experiencing some of the worst flooding in decades. Photo: Rana Sajid Hussain

Some measures that will help to address and prevent devastating floods include:

Hazard assessment and mitigation. Granular data is needed to support hazard assessment, development planning, and monitoring in a vast number of watersheds, though obtaining this level of data is a challenge. Hydro-meteorological observations and remote sensing technologies would also be invaluable. The capacities of local governments and communities need to be enhanced to fill the gaps and promote sustainability. 

Development planning. Integrated watershed management is needed. It advocates coordinated development planning at a watershed scale with collective efforts by administrations and many other stakeholders.

Land use regulations.  Illegal human encroachment on river corridors should be controlled through enforcement of land-use regulations. Rock and sand mining policies and plans should be based on sound scientific analysis.

Watershed conservation. A wide range of nature-based solutions are needed. They include reforestation, wetland restoration, and land-use regulation. These measures will help intercept rainfall, delay rainfall runoff, and minimize soil erosion and therefore flood severity. In a complex land-use and development scenario of a watershed, flood management is becoming more difficult, so it’s important to integrate these measures into the socio-economic development plan.

River training. Installing sediment barriers, inserting boulders, enhancing riverbank and riverbed protections, and other such measures are needed to ‘train’ the river to find its equilibrium and not change course. These measures will also aid rivers to maintain water and sediment balances, in order to protect alluvial fans from flooding and erosion. This way, flood management investment in downstream areas with large infrastructure like flood dikes and others can be reduced.

Long-term forecasting. In the first quarter of 2022, temperatures in several parts of Asia and the Pacific soared higher than 50°C, followed by several dry spells and drying-up of rivers, and later by numerous landslides and floods. It seems that flood events can be triggered by such climate anomalies, but there is hope that the scientific community will continue exploring the links between these events to improve long-term flood forecasting and early warning at a regional scale so countries can prepare better.

The recent devastating floods have shown that both immediate and long-term corrective actions are needed in the region. These actions will only become more urgent as the effects of climate change continue to impact vulnerable communities in these areas.