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Effect of cut-off wall on freshwater storage in small islands considering ocean surge inundation.
- Source :
-
Journal of Hydrology . Dec2021:Part D, Vol. 603, pN.PAG-N.PAG. 1p. - Publication Year :
- 2021
-
Abstract
- • Cut-off wall can prevent lateral and vertical seawater intrusion. • Cut-off wall does not slow down the post-inundation recovery of freshwater storage in early stage. • Cut-off wall slows down the average recovery in high permeability islands. Freshwater lenses (FWL) underneath islands are often unique freshwater resources. Constructing cut-off walls in coastal islands to increase the FWL size has been proposed and tested effective. Meanwhile, seawater inundation induced by ocean surges on low-lying islands can cause the vertical intrusion of saltwater and salinization of FWL. Constructing cut-off walls can influence the post-inundation recovery once the FWL is salinized during the inundation. This influence has not been investigated and considered when discussing the feasibility of cut-off walls. In this study, we numerically simulated an ocean-surge inundation on a 2D, vertically oriented island constructed with a cut-off wall, using a coupled surface–subsurface approach. We varied the aquifer permeability and the depth of the cut-off wall. The effect of the cut-off wall on FWL was quantitatively assessed in terms of FWL volume and flushing time. The results show that the cut-off wall can significantly increase the volume of FWL, confirming previous studies, especially when it is constructed in high-permeability (>10−10.5 m2) islands and deeper. In addition, the cut-off wall can significantly reduce seawater infiltration by up to 40% during the inundation. Therefore, the recovery tends to be accelerated in the early stage, and in islands of low & intermediate permeability. However, the average recovery in high-permeability islands can be slowed down, because the cut-off wall reclaims larger and deeper space that is harder for flushing. As a first attempt to assess the feasibility of the cut-off wall construction from the perspective of FWL recovery, our study is important for the management of freshwater on islands facing the risk of ocean-surge inundation. [ABSTRACT FROM AUTHOR]
- Subjects :
- *FLOODS
*FRESH water
*ISLANDS
*SALTWATER encroachment
*AQUIFERS
*SALINIZATION
Subjects
Details
- Language :
- English
- ISSN :
- 00221694
- Volume :
- 603
- Database :
- Academic Search Index
- Journal :
- Journal of Hydrology
- Publication Type :
- Academic Journal
- Accession number :
- 153974199
- Full Text :
- https://doi.org/10.1016/j.jhydrol.2021.127143