Assessing climate change impacts on the stability of small tidal inlet systems: Why and how? (original) (raw)

Abstract

Bar-built or barrier estuaries (here referred to as Small tidal inlets, or STIs), which are commonly found along wave-dominated, microtidal mainland coasts, are highly likely to be affected by climate change (CC). Due to their predominance in tropical and subtropical regions of the world, many STIs are located in developing countries, where STI related activities contribute significantly to the national GDPs while community resilience to coastal changes is low, with the corollary that CC impacts on STIs may lead to very serious socioeconomic consequences. While assessing CC impacts on tidal inlets is in general difficult due to inherent limitations of contemporary numerical models where long term morphodynamic simulations are concerned, these difficulties are further exacerbated due to the lack of sufficient model input/verification data in often data poor developing country STI environs. As a solution to this problem, Duong et al. (2016) proposed two different process based snapshot modelling approaches for data poor and data rich environments. This article demonstrates the application of Duong et al.'s (2016) snapshot modelling approach for data poor environments to 3 case study sites representing the 3 main STI types; Permanently open, locationally stable inlets (Type 1), Permanently open, alongshore migrating inlets (Type 2) and Seasonally/Intermittently open, locationally stable inlets (Type 3). Results show that Type 1 and Type 3 inlets will not change Type even under the most extreme CC driven variations in system forcing considered here. Type 2 inlets may change into Type 1 when CC results in a reduction in annual longshore sediment transport. Apart from Type changes, CC will affect the level of inlet stability and some key behavioural characteristics (e.g. inlet migration distances, inlet closure times). In general, CC driven variations in annual longshore sediment transport rates appear to be more relevant for future changes in inlet stability and behaviour, rather than sea level rise as commonly believed. Based on model results, an inlet classification scheme which, for the first time, links inlet Type with the Bruun inlet stability criteria is presented.

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