Author(s): Gerald Muller; Charlie Royal
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Abstract: In arid environments, rainfall often occurs in one or two concentrated events per year. This leads to so-called flash floods, rivers which flow in otherwise dry valleys for several hours or days. Today, most of the work on flash floods is aimed at flood management and mitigation. Retaining the water with dams and reservoirs is difficult because of the high sediment load of the flash floods, and because of evaporation. Consequently, the water of the flash floods is lost. In the Roman Empire a very specific solution was developed to address this problem. 2 to 2.5 m high dams were built across dry valleys or wadis to collect the sediment of the flash floods to create farmland. Once the reservoir space had been filled up, the next flash flood would be slowed down so that part of the water could seep into the ground and remain there. Spillways were located at both sides of the dam to maximize the residence time of the water. Today, the technology is only of interest to archaeologists and seems nearly forgotten. It may however be a possibility to reduce water scarcity in arid countries and certainly deserves further development.
Year: 2024