An integrated approach for physical, economic, and demographic evaluation of coastal flood hazard adaptation in Santa Monica Bay, California

Abstract

The increased risk of coastal flooding associated with climate-change driven sea level rise threatens to displace communities and cause substantial damage to infrastructure. Site-specific adaptation planning is necessary to mitigate the negative impacts of flooding on coastal residents and the built environment. Cost-benefit analyses used to evaluate coastal adaption strategies have traditionally focused on economic considerations, often overlooking potential demographic impacts that can directly influence vulnerability in coastal communities. Here, we present a transferable framework that couples hydrodynamic modeling of flooding driven by sea level rise and storm scenarios with site-specific building stock and census block-level demographic data. We assess the efficacy of multiple coastal adaptation strategies at reducing flooding, economic damages, and impacts to the local population. We apply this framework to evaluate a range of engineered, nature-based, and hybrid adaptation strategies for a portion of Santa Monica Bay, California. Overall, we find that dual approaches that provide protection along beaches using dunes or seawalls and along inlets using sluice gates perform best at reducing or eliminating flooding, damages, and population impacts. Adaptation strategies that include a sluice gate and partial or no protection along the beach are effective at reducing flooding around inlets but can exacerbate flooding elsewhere, leading to unintended impacts on residents. Our results also indicate trade-offs between economic and social risk-reduction priorities. The proposed framework allows for a comprehensive evaluation of coastal protection strategies across multiple objectives. Understanding how coastal adaptation strategies affect hydrodynamic, economic, and social factors at a local scale can enable more effective and equitable planning approaches.

Using dune restoration on an urban beach as a coastal resilience approach

“…Our study findings suggest that passive restoration of dynamic beach and dune ecosystems could be used to increase protection and resilience of urban shorelines and their adjacent coastal infrastructure. This restoration project was the first of its kind for the region; it was implemented in a cost-effective manner compared to traditional hardscape alternatives (Aerts et al, 2018;Schroder et al, 2022, Gonyo et al, 2023. The applicability of dune restoration in urban areas requires careful consideration of opportunities and constraints, such as balancing with existing recreational uses, including site specific aspects of feasibility and scalability (Van der Biest et al, 2017).…”

“…For urban coastal communities, nature-based projects that restore beaches and dunes can provide an innovative adaptation strategy to increase the resilience of the coastline to SLR and episodic flooding by creating more natural dune features and geomorphology (Nordstrom et al, 2000;Nordstrom et al, 2012, Walker et al, 2013. These nature-based approaches provide an alternative to traditional methods of hardscaping or armoring, which can have substantial ecological impacts (Dugan et al, 2008;Dugan et al, 2018, Jaramillo et al, 2021 and economic costs (Griggs, 2005;Aerts et al, 2018;Griggs and Reguero, 2021;Schroder et al, 2022). By restoring natural processes and features to impacted urban beach and dune systems, we can improve their ecological and utilitarian functions.…”

Coastal Dune Restoration: A Checklist Approach to Site Selection

“…So far, to manage coastal erosion and increase inland protection against storm impact, defence techniques have primarily included grey engineering structures (e.g., seawalls, jetties, and groins) [19,20]. However, coastal armouring has substantial ecological impacts [21,22] and high economic costs (e.g., [23]) while often failing to achieve the expected results, being unable to follow natural coastal dynamics [24,25]. Measures such as beach nourishment have been partially successful in mitigating coastal erosion, but they are short-term solutions that need to be repeated over time [26][27][28][29].…”

Co-Creating Climate Adaptation Pathways in Coastal Cities: A Practical Guide for Engaged Scholars and Urban Designers

“…Therefore, this study approaches climate adaptation as an engaged scholarly activity, involving communities and stakeholders every step along the way. The literature already suggests that stakeholder involvement is a critical tool to address uncertainty and build acceptance around physical and socio-economic impacts [15]. However, it lacks to provide a generic framework on how to combine research-based approaches by proactively involving community members as an integral component of the research method.…”