Flash floods from threat to opportunity
Implement best management practices (BMPs) that have been successful in other places of the world like use of low-impact development (LID) methods such as permeable roads, permeable trenches, roof gardens, wetlands or detention and retention ponds.
Published: 05:05 PM,May 11,2024 | EDITED : 09:05 PM,May 11,2024
Frequent flash floods claim lives as well as destroy properties. In the past, due to less development and population, flash floods affected the communities less. Now, flash floods simply happen due to intense rainfalls, poor drainage system, urbanisation and also climate change.
Highways that cross a lot of wadis multiply the risk of flash floods by collecting all the runoff from the whole wadis behind the highway, which works as a small dam with a lot of outlets. Such highways can give rise to flooding on both sides of them. In the upstream they create water logging and in the downstream flash floods. In rural areas as well the development, increase in constructions that sometimes have occupied the territory of the wadi’s put all these communities at risk.
At this point many questions may arise in our mind such as: is flash flood only a problem here in Oman or is it the same for other parts of the world? Can floods be used as a source of water? These questions have been addressed in some countries and they could control the floods, and changed them to an opportunity.
By more comprehensive and integrated planning, the same outcome is possible in Oman in Oman as well. But how? Implement best management practices (BMPs) that have been successful in other places of the world like use of low-impact development (LID) methods such as permeable roads, permeable trenches, roof gardens, wetlands or detention and retention ponds.
Combination of these methods with other water management policies can lead to managing the occurrence of flash floods as well as making use of the large volume of the flood water for other purposes.
Flood water can be used for groundwater recharge, water storage for drinking and irrigation purposes. To have a successful flood management system, the presence of a well-designed and well-maintained drainage system is vital. Such a system guarantees the flood water is let to move in a controlled manner without imposing risk to the urban or rural areas. Having such flood management systems requires a large investment that needs specific attention in terms of how it must be justified by inclusion of direct and indirect costs of flash floods.
Applications of collected flood water for irrigation, recreational and drinking purposes may not completely cover the costs of the flood management system but along with reduced direct and indirect costs can justify the launch of such projects by the government. In the general terms for a city under the risk of flash floods the common practice is to manage the runoff in three steps, first to control the runoff entering the city through upstream wadis by dams like Al Jifnain Dam in Al Seeb.
The second step is to control the runoff inside the urban areas using LIDs like bioretention swales, permeable pavement, bioretention cells, roof gardens, infiltration trenches, porous asphalt, porous concrete and porous rubber. Bioretention swales are shallow, vegetated, landscaped depressions with sloped sides. They are designed to capture, treat and infiltrate stormwater runoff as it moves downstream.
The third step is to dispose of the flood water through a well-designed drainage system to safe locations such as retention ponds, or wadis without any risk to the people. This collected water can also be used for irrigation or for gardens and plants in the city thereby minimising fresh water for green areas.
Dr Akbar Karimi
The author is Assistant Professor, Civil & Environmental Engineering Department, National University of Science and Technology, Muscat, Oman
Highways that cross a lot of wadis multiply the risk of flash floods by collecting all the runoff from the whole wadis behind the highway, which works as a small dam with a lot of outlets. Such highways can give rise to flooding on both sides of them. In the upstream they create water logging and in the downstream flash floods. In rural areas as well the development, increase in constructions that sometimes have occupied the territory of the wadi’s put all these communities at risk.
At this point many questions may arise in our mind such as: is flash flood only a problem here in Oman or is it the same for other parts of the world? Can floods be used as a source of water? These questions have been addressed in some countries and they could control the floods, and changed them to an opportunity.
By more comprehensive and integrated planning, the same outcome is possible in Oman in Oman as well. But how? Implement best management practices (BMPs) that have been successful in other places of the world like use of low-impact development (LID) methods such as permeable roads, permeable trenches, roof gardens, wetlands or detention and retention ponds.
Combination of these methods with other water management policies can lead to managing the occurrence of flash floods as well as making use of the large volume of the flood water for other purposes.
Flood water can be used for groundwater recharge, water storage for drinking and irrigation purposes. To have a successful flood management system, the presence of a well-designed and well-maintained drainage system is vital. Such a system guarantees the flood water is let to move in a controlled manner without imposing risk to the urban or rural areas. Having such flood management systems requires a large investment that needs specific attention in terms of how it must be justified by inclusion of direct and indirect costs of flash floods.
Applications of collected flood water for irrigation, recreational and drinking purposes may not completely cover the costs of the flood management system but along with reduced direct and indirect costs can justify the launch of such projects by the government. In the general terms for a city under the risk of flash floods the common practice is to manage the runoff in three steps, first to control the runoff entering the city through upstream wadis by dams like Al Jifnain Dam in Al Seeb.
The second step is to control the runoff inside the urban areas using LIDs like bioretention swales, permeable pavement, bioretention cells, roof gardens, infiltration trenches, porous asphalt, porous concrete and porous rubber. Bioretention swales are shallow, vegetated, landscaped depressions with sloped sides. They are designed to capture, treat and infiltrate stormwater runoff as it moves downstream.
The third step is to dispose of the flood water through a well-designed drainage system to safe locations such as retention ponds, or wadis without any risk to the people. This collected water can also be used for irrigation or for gardens and plants in the city thereby minimising fresh water for green areas.
Dr Akbar Karimi
The author is Assistant Professor, Civil & Environmental Engineering Department, National University of Science and Technology, Muscat, Oman