Massive Floods In Derna, Libya : Unmaintained Dams
usanasfoundation 
Commentary
The world is aghast at the disaster in the port city of Derna, Libya brought in by the Storm Daniel along the Mediterranean coast.
The devastation by flooding is unparalleled in the recent history of the modern world.
The area surrounding around the Derna Wadi or valley has been wiped out, broadening the course of river before it joins the Ocean. The massive floods brought in enormous amounts of mud and sludge, washing away anything and everything that came in their way.
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There were no warning signs or time for people to either evacuate or move away from the affected area. It is believed that at least 20,000 people are missing and presumed dead. The actual body count is 10,000.
Dams Washed Away
There were two earthen dams built across the Derna River valley. Both the dams were constructed possibly with brick diaphragm and compressed earth. A close study of these dams demonstrates high-level erosion because of non-maintenance of the various facets of the dam.
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The funnel-shaped spillway entrance without a trashrack looks ancient and would have been clogged, leaving no path for water especially the sludge coming down at high speed
No emergency spillway is observed in both the dams.
The historical imagery shows clearly that the riprap, wave protection and shoreline were eroded probably due to the seepage. The abutments and guides have never been maintained in the last decade. The stone pitching and gravel bed are missing in all available images.
It is horrifying to note that residential areas with proper roads have been constructed on the downstream side of the dam. In the upper dam, tree plantation is observed clearly indicating that seepage was permanent in both the dams. Both the dams have been totally washed away leaving behind some remnants of the diaphragm in both cases.
Comments
The local government has not been maintaining these two dams, probably because the river was almost dry and it was not bringing any revenue.
The erosions on the upstream face, especially of the rock pitching, has spoiled the gravel and was clearly a disaster in waiting.
A wire meshing with some stone and cement combination and a yearly maintenance of the spillway risers would have certainly helped avoid the disaster.
The tree planting and residential areas downstream in the riverbed were massive blunders which can be attributed to the lack of robust and effective dam rehabilitation mechanism and a corrupt administration.
Disclaimer: This paper is the author's individual scholastic contribution and does not necessarily reflect the organization's viewpoint.
Col Vinayak Bhat (Retd) is an OSINT consultant. He is a military intelligence veteran of the Indian Army withh over 33 years in uniform. He has studied Chinese language and has worked as an interpreter in the Indian Army. He specialises in satellite imagery interpretation and analysis. He works mostly on Chinese PLA and Pakistan armed forces.
He analyses conflicts around the world through satellite imagery with special emphasis on nuclear forces. An alumnus of NDA's J/61 course & tweets as @rajfortyseven.
