Effective design of managed realignment schemes can reduce coastal flood risks

Kiesel, Joshua, Schuerch, Mark, Christie, Elizabeth K. , Möller, Iris, Spencer, Tom and Vafeidis, Athanasios T. (2020) Effective design of managed realignment schemes can reduce coastal flood risks. Estuarine, Coastal and Shelf Science, 242 . p. 106844. ISSN 0272-7714

Full content URL: https://doi.org/10.1016/j.ecss.2020.106844

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Effective design of managed realignment schemes can reduce coastal flood risks
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Abstract

Managed realignment (MR) constitutes a form of nature-based adaptation to coastal hazards, including sea level rise and storm surges. The implementation of MR aims at the (re)creation of intertidal habitats, such as saltmarshes, for mitigating flood and erosion risks and for creating more natural shorelines. However, some evidence suggests that the desired coastal protection function of MR schemes (in terms of high water level (HWL) attenuation) may be limited and it was hypothesized that this was due to the configuration of the remaining seawalls, which we refer to as scheme design. The effects of scheme design on within-site HWL attenuation are analysed for six scheme designs that differ in terms of breach characteristics and water storage capacity. The scenarios are established by manipulating the digital elevation model of the site topography to vary the configuration of the old defence line and the breaches.
Our results show that changes in scheme design, particularly storage area and number and width of breaches, had significant effects on the site's HWL attenuation capacity. Decreasing the tidal prism by changing the number and size of breaches, with the site area kept constant, leads to increased modelled HWL attenuation rates. However, average HWL attenuation rates of >10 cm km−1 are only achieved when site size increases. The mean high water depth of each scenario, calculated by dividing tidal prism by MR area, explains most of the variation in average HWL attenuation between all scenarios. Attention to potential within-site hydrodynamics at the design stage will aid the construction of more effective MR schemes with respect to coastal protection in the future.

Keywords:Coastal wetland, High water level attenuation, Coastal restoration, Managed realignment, De-embankment, Coastal protection
Subjects:F Physical Sciences > F840 Physical Geography
Divisions:College of Science > School of Geography
ID Code:40885
Deposited On:18 Jun 2020 11:20

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