Tue, Sep 10, 2013 - Page 8 News List

Deal with floods the natural way

By Wang Jieh-jiuh 王价巨

The pressure placed by floods and droughts will increase. Careful planning is needed, while engineering should be only the final stage in the process.

The view that humans can conquer nature has long prevailed and is an extremely dangerous concept. Both structural and non-structural approaches to diminishing the impact of natural disasters should be considered, but we place too high an expectation on structural approaches, such as continuing to raise embankments and dredging rivers.

The sudden drastic increase in rain in recent years means that building embankments will not be an effective way to prevent flooding. The most effective approach to flood prevention is to find ways to coexist with water and natural disasters by relying on non-engineering flood prevention strategies that work together with the local geography, environment and urban characteristics to return water to the rivers.

Rainstorm management can be effectively integrated with urban water resource management by taking a three-dimensional approach to water conservation. It is not about removing the water, but keeping it in appropriate places, at the same time as considering damage control, pollution prevention, erosion, climate change adaptation and economic efficiency.

Urban water management should start with a focus on paths and total volumes, and it should include accumulation and seep-through mechanisms.

“Accumulation” means providing the possibility of temporarily keeping water at a suitable location, such as a square, a park, a school playground, the atrium of a big building, or other similar locations. Spaces of various sizes can be used for this function, with each location functioning as a storage pool that will diminish surface runoff and peak flood concentrations. These pools can also accumulate rainwater for recycling.

“Seep-through” means allowing water to flow vertically instead of horizontally and letting water purify through the seep-through process, while also replenishing the groundwater. This would also help prevent water from collecting rapidly in one particular place.

Rainstorm management should include countermeasures for spaces of different scale, with plans for the national, regional and urban level. Much research has built up about Taiwan’s environmentally sensitive areas, and this research could be used to create overlay maps to define areas where development should be banned, restricted or allowed.

It should also be possible to take advantage of national land planning to properly prepare different locations to aid in water management. For example in terms of urban planning, consideration should be given to the potential risk for floods when developing new areas, and controls should be applied on land use and urban design based on the special characteristics of rainstorms. In addition, landscape design and water conservation could be integrated by directing urban flood water and purifying surface runoff.

However, rainfall in Taiwan can be very heavy, and any individual facility will have only a limited effect. Only by joining all facilities into a networked system that can deal with the accumulation and use of water in a larger area, will it be possible to turn often damaging water into a resource.

At the individual locations, existing open spaces, unused land and open spaces in direct connection to buildings should be redesigned into key locations for regulating, stopping and accumulating flood water, and each location should also collect local rainwater. In new land developments, overall consideration should be given to the use of and recycling of water resources by minimizing excavation in order to maximize seep-through area in combination with a system for collecting rainwater for recycling.

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