Experimental study on vegetation flexibility as control parameter for wave damping and velocity structure

Smith

et al. 2021

Preprint

Self Cite

As storm-driven coastal flooding increases under climate change, wetlands such as saltmarshes are held as a nature-based solution. Yet evidence supporting wetlands’ storm protection role in estuaries - where both waves and upstream surge drive coastal flooding - remains scarce. Here we address this gap using numerical hydrodynamic models within eight contextually diverse estuaries, simulating storms of varying intensity and coupling flood predictions to damage valuation. Saltmarshes reduced flooding across all studied estuaries and particularly for the largest – 100-year – storms, for which they mitigated average flood extents by 35% and damages by 37% ($8.4M). Across all storm scenarios, wetlands delivered mean annual damage savings of $2.7M per estuary, exceeding annualised values of better-studied wetland services such as carbon storage. Spatial decomposition of processes revealed flood mitigation arose from both localised wave attenuation and estuary-scale surge attenuation, with the latter process dominating: mean flood reductions were 17% in the sheltered top third of estuaries, compared to 8% near wave-exposed estuary mouths. Saltmarshes therefore play a generalised role in mitigating storm flooding and associated costs in estuaries via multi-scale processes. Ecosystem service modelling must integrate processes operating across scales or risk grossly underestimating the value of nature-based solutions to the growing threat of storm-driven coastal flooding.

“…Weighted Means (CWM) of plant trait data from vegetation surveys carried out as part of the CoastWEB project 31,89 ( Supplementary table S15).…”

Section: Experimental Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Coastal wetlands mitigate storm flooding and associated costs in estuaries

Fairchild

Smith

et al. 2021

Preprint

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“…Importantly, the drag coefficient C D is the only parameter that cannot be measured in the field a priori. Therefore, the value C D = 1 is selected based on experimental studies with stiff cylinders in unidirectional flow [59] and waves based on conditions in the Taf Estuary [60]. C D = 1 was also successfully applied in recent modelling studies [54,57].…”

Section: Vegetation Modulementioning

confidence: 99%

Computational Modelling of the Impacts of Saltmarsh Management Interventions on Hydrodynamics of a Small Macro-Tidal Estuary

Veelen

Fairchild

et al. 2020

JMSE

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Saltmarshes are considered as natural coastal defences. However, owing to the large context dependency, there is much discussion over their effectiveness in providing coastal protection and the necessity of additional coastal defence interventions. The macro-tidal Taf Estuary in south-west Wales was chosen as the case study in this paper to investigate the effects of anthropogenic coastal defence interventions such as construction of hard defences, managed realignment, and altering land use of the saltmarshes on the complex hydrodynamics of the estuary. A coupled flow–wave–vegetation model, developed using the Delft3D coastal modelling software, was used. The wave and current attenuation role of saltmarshes during two contrasting storm conditions was modelled, with and without saltmarsh management interventions. The study reveals that certain saltmarsh management interventions can have widespread impacts on the hydrodynamics of the estuary. Altering the land use by allowing extensive grazing of saltmarsh by livestock was found to have the largest impact on wave attenuation, where wave heights on the marsh almost doubled when compared with the no-intervention scenario. On the other hand, managed realignment has a significant impact on tidal currents, where tidal currents reached 0.5 m/s at certain locations. Changes in estuarine hydrodynamics can lead to undesired impacts on flooding and erosion, which stresses the importance of understanding the effects of localized anthropogenic coastal management interventions on the entire estuarine system.

“…The drag coefficient ( ) is the only parameter that cannot be measured in the field a priori. Therefore, the value = 1 is selected based on experimental studies with stiff cylinders in unidirectional flow (Tanino and Nepf (2008)) and waves based on conditions in the Taf estuary (van Veelen et al, 2019).…”

Section: Modelling Approachmentioning

confidence: 99%

Coastal flood alleviation through management interventions under changing climate conditions

Karunarathna

2019

IJDRBE

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Purpose Coastal flooding has disastrous consequences on people, infrastructure, properties and the environment. Increasing flood risk as a result of global climate change is a significant concern both within the UK and globally. To counter any potential increase in future flooding, a range of potential management options are being considered. This study aims to explore future coastal management practice for flood alleviation, incorporating the influence of climate change. Design/methodology/approach The Taf estuary in South West Wales, a macro-tidal estuary which has a history of coastal flooding, was chosen as the case study in this paper to investigate the impact of coastal management interventions such as construction of hard defences, managed realignment or altering land use of affiliated ecosystems such as salt marshes on the complex hydrodynamics and hence flooding of the surrounding areas of the estuary. The study was carried out using a numerical hydrodynamic model of the Taf estuary, developed using the process-based Delft3D modelling software. Findings The role of the selected management interventions on coastal flooding was investigated using an extreme storm condition, both with and without the impact of future sea level rise. The results highlight the scale of the effect of sea level rise, with the selected management interventions revealing that minimising the increase in flooding in future requires careful consideration of the available options. Originality/value This paper explores the highlighted role of coastal management practice in future with the influence of climate change to study how effective alternative methods can be for flood alleviation.