Between a rock and a hard place: Environmental and engineering considerations when designing coastal defence structures

Abstract

Firth, L. B., Thompson, R. C., Bohn, K., Abbiati, M., Airoldi, L., Bouma, T. J., Bozzeda, F., Ceccherelli, V. U., Colangelo, M. A., Evans, A., Ferrario, F., Hanely, M. E., Hinz, H., Hoggart, S. P. G., Jackson, J. E., Moore, P., Morgan, E. H., Perkol-Finkel, S., Skov, M. W., Strain, E. M., van Belzen, J., Hawkins, S. J. (2014). Between a rock and a hard place: Environmental and engineering considerations when designing coastal defence structures. Coastal Engineering, 87, 122-135Coastal defence structures are proliferating as a result of rising sea levels and stormier seas. With the realisation that most coastal infrastructure cannot be lost or removed, research is required into ways that coastal defence structures can be built to meet engineering requirements, whilst also providing relevant ecosystem services so-called ecological engineering. This approach requires an understanding of the types of assemblages and their functional roles that are desirable and feasible in these novel ecosystems. We review the major impacts coastal defence structures have on surrounding environments and recent experiments informing building coastal defences in a more ecologically sustainable manner. We summarise research carried out during the THESEUS project (2009-2014) which optimised the design of coastal defence structures with the aim to conserve or restore native species diversity. Native biodiversity could be manipulated on defence structures through various interventions: we created artificial rock pools, pits and crevices on breakwaters; we deployed a precast habitat enhancement unit in a coastal defence scheme; we tested the use of a mixture of stone sizes in gabion baskets; and we gardened native habitat-forming species, such as threatened canopy-forming algae on coastal defence structures. Finally, we outline guidelines and recommendations to provide multiple ecosystem services while maintaining engineering efficacy. This work demonstrated that simple enhancement methods can be cost-effective measures to manage local biodiversity. Care is required, however, in the wholesale implementation of these recommendations without full consideration of the desired effects and overall management goals. (C) 2013 Elsevier B.V. All rights reserved.authorsversionPeer reviewe

Cool barnacles: Do common biogenic structures enhance or retard rates of deterioration of intertidal rocks and concrete?

“…At the same time, a recognition that artificial structures are often poor ecological surrogates for the natural rocky shores they may replace (e.g., Bulleri and Chapman, 2004;Gacia et al, 2007;Firth et al 2013;Firth et al 2016) is fuelling considerable international effort to develop and test ways of encouraging their colonisation. This includes structural design interventions and retrofit solutions aimed at facilitating settlement and recruitment of benthic species, to support biodiversity and maintain ecological function (e.g., Chapman and Blockley, 2009;Evans et al, 2015;Firth et al, 2014, Firth et al 2016Sella and Perkol-Finkel, 2015).…”

Artificial structures in sediment-dominated estuaries and their possible influences on the ecosystem

“…Despite extensive studies of artificial substrates in Australian estuaries and in European and American coastal waters (see papers on seawalls, pilings and pontoons by Chapman, 2006;Dafforn et al, 2012;Firth et al, 2014;Glasby et al, 2007;Perkol-Finkel et al, 2012;Pister, 2009;Wasson et al, 2005;etc. ), studies on fouling communities on artificial substrates in the Wadden Sea estuaries are still lacking.…”

Rock armour for birds and their prey: ecological enhancement of coastal engineering

“…5.2.1 Key design parameters Previous research indicates that ecological enhancements can be designed to support the assemblages of marine invertebrates on which waterbirds might feed (Coombes et al, 2015;Evans et al, 2016;Firth et al, 2014Firth et al, , 2015. These can be quite simple and inexpensive 'passive' techniques (e.g.…”

“…The rocky intertidal prey species listed in Table 2 respond to passive and active ecological enhancements elsewhere in the UK (including Elmer, West Sussex and Lyme Regis, Dorset (Moschella et al, 2005); Colwyn Bay and Penthyn Bay (Firth et al, 2014); Porthleven and Zennor (Coombes et al, 2015)). Baseline ecological surveys were undertaken to identify key species and their location relative to the proposed footprint of the scheme.…”

“…Coombes et al, 2015;EA, 2008;Firth et al, 2014;Strain et al, 2017). These 'ecological enhancements' improve structural engineering through the selection of ecologically favourable materials and/or niche habitat designs, yet also satisfy engineering performance requirements.…”