Flood Management: MegaStructure vs EcoDesign

In the evolving discussion between water management practices there are always two poles: the conventional engineering solutions and the emerging landscape infrastructure solutions. The conventional practices of stormwater conveyance are typically termed “end of pipe solutions” because they emphasize the need to transport large volumes of water away from flood prone areas as quickly as possible. This approach is nothing less than an afterthought of the development model that is in place. Managing water in this way perpetuates and exacerbate the existing issues that urban areas face. The question to pose here is: should we promote end of pipe solutions in places where ecological alternatives can be successfully implemented?

We are in a moment in time when we can begin to weigh the value of large infrastructure projects as they relate to risk management vs. the sustainable and ecological alternatives as they relate to our future urban landscapes. When large conveyance infrastructure projects are implemented that means that we are still operating under an old paradigm, where less natural processes are put to work for our benefit. Retrofitting our cities to be water sensitive requires more hard work and more interdisciplinary creativity, making it less desirable in the short term.

Take for example the case of the massive water discharge tunnel near Tokyo, a vast complex built to combat floods. Featured in a recent video report by CNN titled “Fighting floods with an engineering feat”, Andrew Stevens explains that a series of 5 massive underground storage tanks, each 30m in diameter, move water from one place to another via a 6km long tunnel. According to Stevens, the drainage system’s purpose is to avoid the flooding of the rivers above, accommodating water and then slowly releasing it into the Eddo River in a mega infrastructural “feat” to eliminate flood risk. Curiously in the report Takashi Komiyama (Chief of the Outer Flood way Management Office) explains that: “This region is near Tokyo and has been developing at a very fast rate. Before the region had many more rice paddies that acted as drains for the rain water, but those have been replaced by roads and houses and there is a higher risk of floods.”

His statement makes it clear that even though the design answer is well known, the preferred solution remains a conventional one-liner. Finally the report ends with the statement: “A complex solution to an age old problem”. But in reality this is really the conventional solution to the age old problem. What this project is NOT is a “sustainable solution”. Restoring the natural pre-development settings would have required the re-introduction of natural features to accommodate water. That in turn would have benefited the fauna and flora of the region, improved the urban amenities for residents, and reduced heat island effect and pollution. The indirect benefits of such a large investment would have yielded more returns, not just with respect to flood alleviation, but with respect to ecosystem services, coastal management, groundwater resources, etc. In conclusion, although this report is well intentioned it is inappropriately archived in the eco-solutions section of CNN. Instead of a mega “drain” CNN should have showcased an ecological design solution. At urban hydrologics we believe that proper approaches to this widespread challenge should begin with watershed based planning: retrofitting existing urban hard-scape to meet the run-off coefficient of the pre-development rice paddies that, according to the engineer, acted as the — original, optimal and natural — drains.

Text excerpt credits: CNN.com | Fighting floods with an engineering feat | Report by Andrew Stevens | Jan, 09 2012
Image credits: CNN.com | Fighting floods with an engineering feat | Report by Andrew Stevens | Jan, 09 2012

To view the Video Report please click HERE 

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