Decentralized Management Hinders Coastal Climate Adaptation: The Spatial-dynamics of Beach Nourishment

Abstract

Climate change threatens to alter coastline erosion patterns in space and time and coastal communities adapt to these threats with decentralized shoreline stabilization measures. We model interactions between two neighboring towns, and explore welfare implications of spatial-dynamic feedbacks in the coastal zone. When communities are adjacent, the community with a wider beach loses sand to the community with a narrower beach through alongshore sediment transport. Spatial-dynamic feedbacks create incentives for both communities to nourish less, resulting in lower long-run beach width and lower property values in both communities, a result that parallels the classic prisoner's dilemma. Intensifying erosion-consistent with accelerating sea level rise-increases the losses from failure to coordinate. Higher erosion also increases inequality in the distribution of benefits across communities under spatially coordinated management. This disincentive to coordinate suggests the need for higher-level government intervention to address a traditionally local problem. We show that a spatially targeted subsidy can achieve the first best outcome, and explore conditions under which a second-best uniform subsidy leads to small or large losses.

Masked Shoreline Erosion at Large Spatial Scales as a Collective Effect of Beach Nourishment

“…This suggests that, in addition to getting redistributed across the shoreface, if some nourishment sand is redistributed laterally by wave-driven gradients in alongshore sediment transport, neighboring coastal communities may benefit from each other's nourishment investments (Lazarus, McNamara, et al, 2011). A community that does not invest in beach nourishment may still benefit from the beach nourishment projects of its neighbors-in resource economics, a dynamic related to the 10.1029/2018EF001070 prisoner's dilemma known as "free-riders" and "suckers" (Gopalakrishnan, McNamara, et al, 2016;Williams et al, 2013).…”

Climate Change and Human Migration as Adaptation: Conceptual and Practical Challenges and Opportunities

“…Nevertheless, involuntary rural-urban migration often replaces one set of risks with another, especially when urban destinations are poorly equipped to provide basic human necessities to the new migrants. Thus, migrants affected by climate change at their places of origin may become exposed to a second level of stress at urban destinations, where new hazards may reinforce existing vulnerabilities (McNamara et al 2016).…”

“…Hard protection methods also require routine maintenancein fact, countries across the globe are enhancing their hard-engineered structures, such as levees and dikes, to accommodate climate change-induced flooding (Harman et al 2015;Deltacommissie 2008;Ligtvoet et al 2012); yet, as demonstrated by Schmidt et al (2013), stakeholders gravitate toward hard protection measures over other adaptation alternatives. Highly developed or tourist-oriented coastlines greatly contribute to a coastal community's economy, and constructing hard defense structures leaves the coastline relatively unaltered from its current, highly attractive statean explanation for the observable, global preference for this adaptation method.…”

“…Soft defenses create aesthetically pleasing coastlines that offer an organic defense system with natural adaptive abilities. Soft defenses such as beach nourishment simply build on a natural system in place, resulting in an adaptation with the ability to withstand high-energy coastal systems and events (Harman et al 2015), decreasing storm-induced damage (Gopalakrishnan et al 2016). Gopalakrishnan et al (2016) define beach nourishment as a process that regularly repairs or restores the eroded surfaces of beaches using externally dredged sand.…”

Geoengineering Coastlines? From Accidental to Intentional

“…Similarly, a beach nourishment (beach extension/ construction) project that creates a subtle seaward bump in the shoreline can increase the rates of net sediment delivery to adjacent beaches. When towns implement localized stabilization policies, not accounting for the physical and economic implications of these dynamic spatial interactions, it results in suboptimal outcomes relative to coordinated management of the coastline (Gopalakrishnan et al, 2014).…”