Broader vision, lower risk

Posted on December 15, 2009


Although river improvement activities are now widespread, they typically have a local focus, with the aim of improving ecological and hydrological function at the reach scale.  If river interventions can be developed and coordinated in a broader context – for example, across a river basin – there are potential gains to be made in terms of system-wide efficiency.  A Chinese study, atJinannearBeijing, shows how a basin-scale approach can be used to better manage the impacts of urbanisation and climate change on drought and flooding.   For individual tributories, instream flow requirements were calculated and the best ways of reducing flood or drought risk were determined: options included channelisation, building reservoirs to store runoff, building levees to reduce flooding, diverting water to replenish dry reaches, closing waterworks to protect groundwater, and greening banks to conserve surface water.  Network analysis was then used to optimise connections between lakes, reservoirs and wetlands to minimise overall risk.  The redesigned network reduced flood risk to less than half the original level.  The outcomes of the study supported the use of retention wetlands rather than traditional hard engineered structures to relieve flood risk.  Lining revetments with vegetation rather than hard materials was recognised as having benefits for fish repopulation, water purification, nutrient transport and waterfront greening, as well as being a better, more sustainable solution for flood control.

References:

Cui, B., Wang, C., Tao, W. & You, Z.  2009.  Riverchannel network design for drought and flood control: A case study of XiaoqingheRiver basin, Jinan City, China.  Journal of Environmental Management 90, 3675–3686.

 Cohen, M.J., Brown, M.T., 2007. A model examining hierarchical wetland networks for watershed stormwater management. Ecological Modelling 201, 179–193.

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