Climate change adaptation related to structural parameters of coastal vegetation

[Description of methods used for collection/generation of data] Collection of data from extraction of articles retrieved from the literature (Web of Knowledge and SCOPUS, accessed July 2015 and updated May 2021). Papers reporting estimates of the effect of coastal plants on current and wave attenuation in vegetated coastal habitats identified using search terms: “Seagrass*” [All Fields] OR “Mangrove*” [All Fields] OR “Salt marsh*” [All Fields] OR “Macrophyte*” [All Fields] AND “engine*” [All Fields] OR “wave attenuation” [All Fields] OR “flow modification” [All Fields]. The in total 963 papers retrieved were analyzed for quantitative estimates, supplemented with papers and documents containing data meeting the requirements of the analyses contained within the references of the papers retrieved, resulting in a data set containing a total of 1372 estimates derived from 95 individual articles with a temporal cover from 1982 to 2020.[Methods for processing the data] Results from field and laboratory studies were used, but not numerical models. When information was given for multiple observations with different vegetation parameters and/or hydrodynamic parameters, we included several data points per study, but only included 1 measurement (max. distance) when the same structural parameters had repeated measurements for different distances within the vegetation. Where authors reported values for current reduction these were used directly, always making sure a non-vegetated (bare) reference value was used to calculate reduction in the vegetation. When data was (re)calculated from separate reported values the formulas used for current reduction, dU, were calculated as: dU/U0 = (U0-Uv)/U0 With U as the current speed over a reference unvegetated region U0 and through a vegetated region Uv in m s-1 respectively. Where the information was provided in the selected studies, we calculated the wave energy reduction, dE, defined as (Knutson et al. 1982): dE/E0 = ((E0-Ev))/E0 Where E is the energy without vegetation (E0) and within the vegetation (Ev) respectively. The wave height reduction per meter r (Mazda et al 1997) was calculated as: r = dH/(H0x) = ((H0-Hv))/(H0x) Where x is the length of the vegetation field. When multiple measurements were done with the same vegetation settings (i.e. density, water height) at different distances into the vegetation, we took the maximum distance evaluated. The effect of vegetation on current and wave attenuation was represented by the decay coefficients, KiH, (Kobayashi et al., 1993) and KiU (m-1), representing the relative decrease in significant wave height (KiH), and current velocity (KiU) with distance into the vegetated fringe (x, bed length) calculated as, kiH=1/x ln(1-dH/H0 )=1/x ln(Kt ) and kiU=1/x ln(1-dU/U0 ) Where Kt is the wave transmission coefficient. We used the same literature sources that were used for the data were collection, to compile relevant vegetation structural parameters, specifically, shoot or stem density and emergence ratio (defined as hveg/h). For stiffness we used Young’s bending modulus (E, in N mm-2), when this parameter was not available from the same source, we completed the data with species specific values from literature (e.g. Zhu et al. 2020 for salt marshes, de los Santos et al. 2016; La Nafie et al. 2012; Soissons et al. 2017 for seagrasses and van Hespen et al. 2021 for mangroves). When no value was known, the value for the family was used or an average for the group (i.e., saltmarsh, seagrass, etc.) obtained from the compiled values.[Relationship between files] Readme provides background information for xlsx datafile.[People involved with sample collection, processing, analysis and/or submission] https://casrai.org/credit . Idea and concept C.M.D and I.J.L, design and discussion of content during workshops I.E.H., N.M., B.v.W., T.J.B., I.J.L, C.M.D. Database compilation I.E.H, M.M., A.G.M and N.M. Analysis of data I.E.H.. All authors contributed to the writing and editing of the manuscript.Funding for this data collection supplied by the MedShift project, CGL2015-71809-P (MINECO/FEDER) and baseline funding from King Abdullah University of Science and Technology to C.M.D. I.E.H. was supported by grant RYC-2014-15147, co-funded by the Conselleria d'Innovació, Recerca i Turisme of the Balearic Government (Pla de ciència, tecnologia, innovació i emprenedoria 2013-2017) and the Spanish Ministry of Economy, Industry and Competitiveness.Data_coastal_vegetation_adaptation.xlsx, readme.txtPeer reviewe

Managing erosion of mangrove-mud coasts with permeable dams – lessons learned

International audienceMangrove-mud coasts across the world erode because of uninformed management, conversion of mangrove forests into aquaculture ponds, development of infrastructure and urbanization, and/or extraction of ground-water inducing land subsidence. The accompanied loss of ecosystem values, amongst which safety against flooding, has far reaching consequences for coastal communities, exacerbated by sea-level rise. To halt erosion various nature-based solutions have been implemented as an alternative to hard infrastructure sea defenses, including mangrove planting and erection of low-tech structures such as bamboo fences, permeable brushwood dams, etc. These structures have been designed on the basis of best-engineering practice, lacking sufficient scientific background. This paper investigates the use and success of permeable dams over a period of about 15 years, describing their application in Guyana, Indonesia, Suriname, Thailand and Vietnam, summarizing the lessons-learned, and analyzing their functioning in relation to the physical-biological coastal system. Also an overview of relevant costs is given.The basic philosophy behind the construction of permeable dams is the rehabilitation of mangrove habitat through re-establishment of the (fine) sediment dynamics - we refer to Building with Nature as the overarching principle of this approach. Our main conclusions are that a successful functioning of permeable dams requires (1) a thorough understanding of the physical-biological system and analysis of the relevant processes, (2) patience and persistence, including maintenance, as the natural time scales to rehabilitate mangrove green belts take years to decades, and (3) intensive stakeholder involvement. We give a list of conditions under which permeable dams may be successful, but in qualitative terms, as local site conditions largely govern their success or failure