Flash Flooding in UAE: Could have been avoided?
Risk of flash flooding in UAE very well known.
Changes in land use arising from enhanced urbanization over last few decades. And as a result, hydrological consequences associated with flood risk needs to be faced, particularly, shorter times to peak discharges.
Still, under normal circumstances, 147 mm in a day is not at all a big spell to be concerned about. However, UAE has altogether has a peculiar hydrological system.
1. UAE does not have rivers flowing downhill.
2. UAE’s flood terrain remains characterized not by conventional water, but by wind (which is no more stable under the flow of water).
Flood water has to flow along the base of the dune formations, dictated by wind direction. And, these dunes in UAE vary over orders of magnitude (some running for few tens of meters, while others running for tens of kilometers)
3. A highly variable infiltration rates across the entire catchment.
4. Establishing connectivity between overflowing upstream ponds and subsurface flow paths remains a basic problem.
5. Scouring and erosion dictating the variations in the course of surface water flows.
6. Absence of natural river mouths discharging floodwaters into the Sea.
I know very little about your system. You may look into hydrophobicity, sometimes evident in extremely dry conditions, the soils cannot absorb or infiltrate much water until they break down the hydrophobicity and begin to absorb and infiltrate more water. Under this condition of hydrophobicity, perhaps surface flow occurs and tends not to channelize. It may help explain excess runoff and flooding with less channelization. Of course urbanization could also contribute due to added impervious surfaces, compaction, etc.
Flash flood is a disaster and disaster cannot be avoided.
But mitigation measures may reduce the impact of this disaster.
Currently, flash flood mapping project in Oman is underway.
Perhaps, in future, they may be able to combat against the harsh impacts.
Regards
Ijaz
Sure, it could have been managed better through risk reduction systems including both structural and non structural measures. In addition, such these systems need to be paid lots of attention at nation-and worldwide scales.
Well, sure. It could have been avoided. Most are engineers in this thread (not me, full disclosure), so you know--we can build anything to manage any flows produced by any event you'll likely encounter (at least for some period of time). But, of course, the question is, should we? It's always a balance between stormwater management infrastructure lifespan versus the chance of seeing a large, rare event when you decide what to build and decide what to spend on such facilities. At this stage, as the climate continues to adjust to excessive GHGs, my advice is to buy the land one needs for future expansion of stormwater facilities, but build infrastructure now that is sized more closely to today's expected flows. It's possible all of this is happening in the UAE now, but I know nothing about their programs and have no time today to head down a google rabbit hole to learn them. Perhaps others can chime in on what goes on there. Cheers!