Remarkably, the duration of this year’s floods will not stretch longer than the floods in 1988. There are two reasons for this: The water level at the Ganges river is far below the “danger level,” meaning the water is able to flow speedily into the Bay of Bengal. Second, the moon’s weak gravitational pull at the time of the flooding allowed the water to flow more quickly.
So far, the 2016 floods have washed out over 1200 fishing enclosures and submerged around 50 villages. The flooding began with intense rainfall at the foothills of the Himalayan mountains, and over the Meghalaya basin during the middle of July.
Flooding in the Brahmaputra basin in particular came from the Teestra, Dhalara, Dudkumar, and Brahmputra rivers.
Yet we should remember the causes of flooding are not only natural, but also man-made. The combination of cutting down trees, filling up wetlands, continuing to build large urban constructions, and not maintaining embankments properly all play a role in increasing the intensity and duration of floods.
Many of us were surprised to find that Dhaka avoided flooding this year. Instead of making the city more susceptible to floodwater, the expansive urban development diverted floodwater into nearby rivers such as the Turag, Balu, and Buringanga.
Unfortunately, this means that people living in nearby settlements such as in Manikganj, Faridpur, and Shariatpur will experience prolonged inundation as the water was unable to enter through the old Brahmaputra channel.
While forecasting floods is crucial for protecting people from disaster, forecasts can only be accurate up to five days. A 10 day or more forecast is unrealistic because weather conditions are chaotic and unpredictable. Slight changes in the atmosphere greatly impact the accuracy of forecasts.
Long-term climatic cycles may prove more useful in forecasting floods. Most major floods in Bangladesh in recent years have occurred during the cold phase of what’s called the El Niño-Southern Oscillation cycle: In 1988, 1998, and 2007. This cycle occurs over every few years as sea surface temperatures and air pressure circulates across the Pacific Ocean; and so could be useful for future flood predictions.
Across the planet right now, intense rainfall has flooded parts of the state of Louisiana in the United States, breaking water level records and displacing thousands.
By current estimates, there is a 1-in-500 chance that such flooding will repeat any time soon. Although scientists are yet to link either of these floods to climate change, the latest Intergovernmental Panel on Climate Change report suggests heavy flooding is set to increase in both these regions.
A timely reminder that as climate change worsens, communities around the world – not just in Bangladesh – will face more and more extreme environmental hazards.
AKM Saiful Islam is a professor of the Institute of Water and Flood Management at the Bangladesh University of Engineering and Technology. He can be emailed at [email protected]