As the twin disasters of flash flooding and persistent drought plague arid regions across the globe, The Earth & I reached out to esteemed hydrologist and educator, Dr. Radwan Al-Weshah, for his views on the situation in South Sinai, Egypt. What are science and tradition doing to address the crisis there?
Sinai is Devastated by Flooding and Drought
In most arid regions in the Middle East and North Africa, the problems of flash flooding and drought pose a serious threat to human life and livelihoods. Flash flooding—a surface water response to intense and sudden rainfall—can occur rapidly with almost no lead time, resulting in damage from high flow velocities and heavy sediment loads.
Flash flooding can damage or destroy infrastructure, livestock, and local plants and animals while causing serious health impacts, including death, injury, contamination of drinking water, disease, and the displacement of people.
South Sinai, Egypt, is no stranger to the devastation of natural disasters. The South Sinai region of the Sinai Peninsula is devoid of local freshwater sources and cannot transport water from the distant Nile River basin. The lack of sustainable surface water, limited shallow groundwater resources, and devastating and frequent cycles of flash flood incidents lead to exceptionally severe drought on the one hand and damage from flood water inundation on the other.
Worse still, increased human activity and expanding human settlements in the region have exacerbated the impacts of flash floods, leading to greater loss of life and resultant socioeconomic problems.
Harvesting Floodwater for Drought-Stricken Communities and Crops
However, there is hope to reduce these negative impacts through the use of flood risk and disaster mitigation response tools. Particularly in areas where drought is also a problem, developing ways to collect flash flood water and store the excess in reservoirs or soil moisture can positively address both catastrophes.
Recently, a number of studies were conducted for flood prediction and mitigation in different wadis—dry channels that carry water during the rainy season—in the Sinai Peninsula of Egypt. One study presented a method for predicting the floodwater runoff volume using geographic information system (GIS) mapping and hydrological models and discussed ways of mitigating flood hazards in Sinai using small dams and open channels.
Another innovative study presented a comprehensive analysis of protection from flood risks, a rainwater harvesting process, and a way to link their system to the recharging of groundwater aquifers using different hydrological models—all designed as part of a flood mitigation plan for Wadi Watier in South Sinai, Egypt.
New studies such as these can be used effectively by decision makers to integrate surface and groundwater hydrology to mitigate and harvest flash flood water.
Large-Scale Dams Stop Flooding at a Price
Generally speaking, flood mitigation and risk management studies focus on what are called hard or soft engineering projects.
Hard engineering (structural) projects are ones that involve the construction of artificial structures that, through a combination of science, technology, and a bit of brute force, prevent a wadi from flooding. Hard engineering projects are generally very successful and have a large impact on wadis. Unfortunately, the effects of a hard engineering project can disrupt ecological systems in the drainage basin.
The high cost, technological requirements, and ongoing maintenance of “hard-engineered” projects make them unfeasible in countries without significant economic resources.
Hard engineering structures such as dams generally involve the containment of large volumes of water so if they were to fail for some reason, the impacts could be many times worse than if the wadi had been allowed to flood naturally. There is also the high cost and technological and maintenance requirements of hard engineering projects that make them unfeasible in countries without significant economic resources.
The People of Sinai are Doing Their Best with Sustainable, Affordable Solutions
Soft engineering projects—nonstructural, lower cost mechanisms that suit the region’s technical and socioeconomic conditions—use natural resources and local people’s knowledge of the wadi to reduce risks posed by flooding without trying to prevent flooding entirely. Soft engineering projects are significantly cheaper than hard engineering projects, making them more suitable for less developed countries. Their construction, maintenance, and technology requirements are such that they can be implemented by local people in remote parts of poorer countries.
Soft engineering projects are also more sustainable than their hard engineering counterparts because they do not disturb the natural processes and ecological systems in wadi basins, choosing instead to integrate with natural structures and, in some cases, improve them.
An underground concrete reservoir is one of the most appropriate water harvesting techniques for South Sinai, in part because it is easily maintained by the Bedouins who live there. Bedouins also capture floodwaters in hafirs—constructed earthen catchment ponds—and use cisterns to harvest rainwater for domestic and livestock uses.
Low-cost gabion dams—consisting of wired-together mesh baskets filled with stones to form a flexible wall—used with underground reservoirs have been highly requested by local stakeholders.
In addition, low earthen or stone dykes in the wadi beds (locally known as Oqum) are commonly used. Oqum are usually protected by remnants of vegetation.
In some cases, the natural recharge of shallow groundwater aquifers can occur in the sediment deposits in wadi depressions.
The total amount of rainfall and flash flood water that could be utilized annually in North and South Sinai is estimated to be around 1.3 billion cubic meters.
The total amount of rainfall and flash flood water that could be utilized annually in North and South Sinai is estimated to be around 1.3 billion cubic meters. Some studies suggest that this quantity could even be increased to 1.5 billion cubic meters.
In order to harvest and use the water from flash floods, it is necessary to identify the locations of potential water harvesting sites. GIS and remote sensing with distributed watershed models are being used by scientists and engineers as effective tools to identify these locations.
Modern watershed modeling systems (WMS) have proven to be highly effective in mapping, investigating, and modeling the runoff processes and optimization of the rainwater harvesting.
WMS use satellite imagery to determine a series of measurements including the water flow and drainage capacities of an area, maximum flow distance, overland flow distance, basin slope, basin area, the volume of the annual flood, and basin length.
Armed with this data, hydrologists can calculate flashflood total discharges and identify storage capacity. The end product? WMS models can help in locating potential areas suitable for surface water harvesting and promote the percolation of trapped water into the alluvium (sand and gravel sediment) aquifers.
Though scientists are armed with increasingly sophisticated technology and local traditions assist with addressing the hydrological issues in South Sinai, significant challenges remain for hydrological engineers and others to solve the flood and drought nexus there. Further study and political will are required to design and build sustainable water management systems that can put an end to frequent flash flooding and persistent drought in this and other arid regions of the world.
*Radwan A. Al-Weshah is a Professor of Civil Engineering and former Dean of Scientific Research at the University of Jordan in Amman. Dr. Al-Weshah is a senior academic leader, professional technical consultant, and devoted educator in hydrology and water resource engineering. His leadership in engineering analysis, modelling in hydrological studies of floods and flood risk mapping, and design of major hydraulic structures extends throughout the Middle East and other parts of the globe.