The Effectiveness of Nature-Based Solutions in Mitigating Salt Intrusion in Estuaries

Abstract

Climate change and anthropogenic activities are enhancing salt intrusion in many estuaries, which reduces the supply of drinking water as well as freshwater for agricultural and industrial uses and can further cause severe economic losses. Nature-based solutions emerge as sustainable and ecologically sound strategies to mitigate salt intrusion in estuaries. This review paper explores the effectiveness of nature-based solutions in salt intrusion mitigation. Advances in the understanding of estuarine salt dynamics are summarized, thus identifying the dominant parameters that determine the salt intrusion in different types of estuaries. Six potential nature-based solutions (NBSs) for salt intrusion mitigation are conceptualized, including improvement of river discharge management, reduction of channel cross-section, modification of bottom topography, utilization of friction-convergence balance, enlargement of intertidal area and introduction of meanders. These NBSs are grouped into two types: (a) advection-based and (b) mixing-based. Numerical model assessments indicate that all these NBSs have potential to reduce salt intrusion lengths, depending on the salinity structure of the estuary. Nevertheless, applications of NBSs to real estuaries are rare. Directions toward improving the implementation of nature-based solutions for mitigating salt intrusion in estuaries are provided.