As global warming continues to exacerbate sea level rise and extreme weather, our nation’s floodplains are expected to grow by approximately 45 per cent by the century’s end. Here’s how climate change plays a role in flooding, and how we can better keep A flood is the accumulation of water over normally dry land. It’s caused by the overflow of inland waters (like rivers and streams) or tidal waters, or by an unusual accumulation of water from sources such as heavy rains or dam or levee breaches.
This occurs when a river or stream overflows its natural banks and inundates normally dry land. Most common in late winter and early spring, river flooding can result from heavy rainfall, rapidly melting snow or ice jams.
According to a study, approximately 41 million U.S. residents are at risk from flooding along rivers and streams a large wave crashes into a seawall in Winthrop, Massachusetts a day after a nor’easter pounded the Atlantic coast in 2018. Dozens of people were rescued from high waters overnight and warned of another round of flooding during high tide. More than 8.6 million Americans live in areas susceptible to coastal flooding, which happens when winds from a coastal storm, such as a hurricane or nor’easter, push a storm surge a wall of water from the ocean onto land. Storm surges can produce widespread devastation. There are also increasing numbers of shallow, non-life-threatening floods caused by higher sea levels; these high tide floods occur when the sea washes up and over roads and into storm drains as the daily tides roll in. These quick-rising floods are most often caused by heavy rains over a short period. Flash floods can happen anywhere, although low-lying areas with poor drainage are particularly vulnerable.
Also caused by dam or levee breaks or the sudden overflow of water due to a debris or ice jam, flash floods combine the innate hazards of a flood with speed and unpredictability and are responsible for the greatest number of flood-related fatalities. Many factors can go into the making of a flood.
Talking about climate impacts in Bangladesh would hardly be complete without mention of the staggering injustice Bangladesh faces. Because overwhelmingly, climate impacts are being imposed on Bangladesh by high-emitting, wealthy countries, not by the people of Bangladesh themselves. As a country, Bangladesh emits only a tiny fraction of the greenhouse gas emissions causing climate change. Perhaps more telling, the average person in Bangladesh emits 0.5 metric tons of CO2 per year. In the US, for comparison, that number is 15.2 metric tons per person about 30 times as much.
For Bangladesh, for so many other countries, and everyone’s shared future, the time to act on climate change is now.
Take action today and tell the Senate: Pass the strong Build Back Better Act we need to stop global warming and create a brighter future for everyone because 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 30 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 deposits 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 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.
Also, hydro-meteorological observations and remote sensing technologies would be invaluable. The capacities of local governments and communities need to be enhanced to fill the gaps and promote sustainability. Integrated watershed management is needed. It advocates coordinated development planning at a watershed scale with collective efforts by administrations and many other stakeholders. Illegal human encroachment on river corridors should be controlled through the enforcement of land-use regulations. Rock and sand mining policies and plans should be based on sound scientific analysis. A wide range of nature-based solutions is 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.
Installing sediment control dams, 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, to protect alluvial fans from flooding and erosion. This way, flood management investment in downstream areas with large infrastructures 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 on 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.
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. Connecting climate change to floods can be a tricky endeavour.
Not only do myriad weather- and human-related factors play into whether or not a flood occurs, but limited data on the floods of the past make it difficult to measure them against the climate-driven trends of floods today. However, as the IPCC noted in its special report on extremes, it is increasingly clear that climate change has detectably influenced several of the water-related variables that contribute to floods, such as rainfall and snowmelt. In other words, while our warming world may not induce floods directly, it exacerbates many of the factors that do. According to the Climate Science Special Report
(issued as part of the Fourth National Climate Assessment, which reports on climate change in America), more flooding in the United States is occurring in the Mississippi River Valley, Midwest, and Northeast, while U.S. coastal flooding has doubled in a matter of decades. A tractor-trailer is swept off the road by floodwaters in Nebraska in March 2019. Rapid snowmelt combined with heavy rainfall resulted in catastrophic flooding across the Missouri River Basin.
The study determined that these rains were at least 40 per cent more likely and 10 per cent more intense because of climate change. Looking forward, heavy precipitation events are projected to increase (along with temperatures) through the 21st century, to a level from 50 per cent to as much as three times the historical average. This includes extreme weather events known as atmospheric rivers, and air currents heavy with water from the tropics, which account for as much as 40 per cent of typical snowpack and annual precipitation along the West Coast. Experts predict they will intensify, bringing as much as 50 per cent more heavy rain by the end of this century. Of course, heavier rainfall does not automatically lead to floods, but it increases the potential for them.
To that end, we must meet the commitments laid out in the Paris Climate Agreement. As well as supporting key domestic policies, including the Clean Power Plan and automotive fuel efficiency standards, that would slash our nation’s climate-altering pollution. Don’t forget, extreme weather disasters affect all countries, rich and poor. But as we face a future with enhanced risks, it is critical to face the reality of those who bear the burden of our changing climate.
Those living in poverty are the hardest hit by climate change despite being the least responsible for the crisis. Climate change is forcing people from their homes, bringing poverty on top of poverty and increasing hunger. People in poorer countries are at least four times more likely to be displaced by extreme weather than people in rich countries. The world faces a race against time to reduce emissions and help the most vulnerable cope with climate impacts that are already being faced today and will escalate in the years ahead. It’s time to act now.
The writer is a researcher and columnist. He can be contacted at [email protected]