Expert: Dr Kiran Tota-Maharaj
Reader in Civil & Environmental Engineering (Water and Environmental Engineering)
College of Engineering and Physical Sciences, Aston University
1/ Do we have any basic measures on the volume of precipitation that triggered the collapse of the two dams that flooded Derna? How much rain over what period of time? Are there adequate records to put that in historical context? Were any records broken?
Storm Daniel has the characteristics of a tropical depression, approximately 170 millimetres (6.7 inches) of rainfall occurred fell in Libya. Torrential rains of between 150 - 240 mm caused flash floods in several cities, including Al-Bayda, which recorded the highest rainfall rate of 414.1 mm.
2/ Do we know anything about the dams that failed? Where they old, near the end of their expected lifespan? Were they known to be fragile in any way? To what extent, in other words, might this have been a disaster waiting to happen?
Flash floods, which is considered as one of the worst weather-related natural disasters are highly unpredictable following brief spells of heavy rain. This region in Libya is subjected to flash floods, where floods from the mountains causing heavy damage to hydraulic structures and features of Dams. These floods are made up of sudden, unexpected and heavy rains or a strong surge of water, which usually hit the steep sloped mountainous catchments and have inundated many regions in Libya. The sweeping flash floods also led to the death of many residents and great losses of property. Entire neighborhoods in Derna disappeared, along with their residents swept away by water after two ageing dams collapsed making the situation catastrophic and out of control, the city of Derna is surrounded by mountains, so the flash flooding occurred quite rapidly, taking over with surface-water levels rising as high as 3 metres (10 feet). Engineers have previously issued warnings about the risks of these dams bursting and the urgent need to strengthen their defenses, which unfortunately didn’t occur. Early Warning Systems (EWS)- which are effective ways to reduce the risks of flash floods have not been properly implemented. When EWS are issued before a flash flood event, additional time is created to take action and save lives and infrastructure. The unexpected arrival of a flash flood in Libya, combination with its force, limited understanding of the risks and small space-time scales provide explicit challenges for the development and implementation of an EWS system for flash floods.
3/ There is speculation about many thousands of deaths. Is this attributable almost entirely to the failed dams? Or was there massive and deadly flooding beside that?
Thousands of people’s lives have been sadly lost after the massive flood ripped through the city of Derna as a result from the heave storm conditions and excessive rainfall. There have been several areas severely affected by widespread flooding, damage to infrastructure, and loss of life. The disastrous flooding event is likely the cause of the two dams’ collapses, making thousands of residents of the valley and the city of Derna, Libya vulnerable as a result of the storm. Entire neighbourhoods of Derna by the bank of the swollen river had been ravaged and washed away.
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Kiran Tota-Maharaj Reader in Civil and Environmental Engineering
Dr Tota-Maharaj’s areas of expertise include wastewater treatment using microbial fuel cells with bioelectricity production.