THE USE OF GIS IN THE DESIGN OF MANAGED REALIGNMENT SCHEMES

Abstract This paper describes a range of GIS techniques, which have been developed over the last 5 years and successfully employed in the design of over 15 realignment schemes in a range of UK estuaries. A proposed scheme in the Humber Estuary is used to illustrate the applicability of the methods. GIS is seen to be fundamental at all stages of the design process. This starts with establishing the historical site evolution, the current site elevations/gradients, the existing habitats and the nature conservation designations. The paper describes how topographic survey data can be combined with remotely sensed information to create a digital terrain model for the managed realignment scheme, which can then be adapted to create a new 'design' surface for the proposed scheme. Further explanation is given various aspects of scheme design, including (i) the prediction of the habitats which are likely to colonise the scheme, (ii) the need to maintain a sediment balance within the scheme, (iii) the calculation of tidal prisms, and; (iv) the mapping of sampling locations. The GIS analysis provides valuable information for the design, consultation and environmental assessment process. The ability to overlay various layers of information and to create 2 or 3D representations of the scheme, are seen to be particularly powerful GIS features

Sandy coastlines under threat of erosion

Sandy beaches occupy more than one-third of the global coastline(1) and have high socioeconomic value related to recreation, tourism and ecosystem services(2). Beaches are the interface between land and ocean, providing coastal protection from marine storms and cyclones(3). However the presence of sandy beaches cannot be taken for granted, as they are under constant change, driven by meteorological(4,5), geological(6) and anthropogenic factors(1,7). A substantial proportion of the world's sandy coastline is already eroding(1,7), a situation that could be exacerbated by climate change(8,9). Here, we show that ambient trends in shoreline dynamics, combined with coastal recession driven by sea level rise, could result in the near extinction of almost half of the world's sandy beaches by the end of the century. Moderate GHG emission mitigation could prevent 40% of shoreline retreat. Projected shoreline dynamics are dominated by sea level rise for the majority of sandy beaches, but in certain regions the erosive trend is counteracted by accretive ambient shoreline changes; for example, in the Amazon, East and Southeast Asia and the north tropical Pacific. A substantial proportion of the threatened sandy shorelines are in densely populated areas, underlining the need for the design and implementation of effective adaptive measures. Erosion is a major problem facing sandy beaches that will probably worsen with climate change and sea-level rise. Half the world's beaches, many of which are in densely populated areas, could disappear by the end of the century under current trends; mitigation could lessen retreat by 40%.info:eu-repo/semantics/publishedVersio

Uniendo ingeniería y ecología: la protección costera basada en ecosistemas

En un contexto de crecientes impactos y riesgos socio-económicos en las costas del planeta, la protección costera basada en ecosistemas surge como un nuevo paradigma que une los principios de protección, sostenibilidad y resiliencia, a la vez que proporciona múltiples beneficios. Este artículo ofrece una perspectiva sobre qué son y cómo se pueden utilizar las defensas naturales en el diseño, planificación y gestión de costas. La política pública muestra un creciente interés por su implementación general y el cuerpo de conocimiento y experiencia alrededor de la también denominada infraestructura ?verde? es creciente, pero aún existen importantes barreras que salvar. Una de ellas es estandarizar su diseño en términos ingenieriles, así como reconocer los aspectos que los diferencian respecto a enfoques tradicionales. La adaptación climática y la reducción de riesgos son áreas en las que su utilización puede ser más significativa, debido a la variedad de servicios que ofrecen. Tanto desde el punto de vista técnico como económico, existen argumentos sólidos para evitar la degradación de los ecosistemas, avanzando su restauración y conservación, como también desde la perspectiva de la defensa de las costas.In a context of increasing socio-economic impacts and risks in the coastal areas of the planet, coastal protection based on ecosystem features becomes a new paradigm that combines the principles of conservation, sustainability and resilience, while providing multiple benefits. This paper provides a perspective on what these are and how they can be used in the design, planning and management of the coastal zones. Policy-makers are calling for further uptake and implementation across the board and the body of knowledge and experience around the socalled ?green? infrastructure is growing, but there are still major barriers for a widespread uptake. One of them is to standardize designs in engineering terms, recognizing the different characteristics compared to traditional engineering solutions. Climate adaptation and risk reduction are areas where its use may be more significant, for the variety of services they offer. Both technically and economically, there are strong arguments to prevent degradation of ecosystems and to advance in their restoration and conservation, as well as from a coastal defense perspective

International guidance on use of natural and nature-based features in flood and coastal management

Natural and Nature-Based Features (NNBF) have been used for decades to support a variety of objectives in coastal and riverine systems. Some types of NNBF, such as river restoration, use of bio-engineering, wetlands and beach and dune projects, have been a longstanding part of flood risk reduction strategies in Europe, the United States and elsewhere. However, stimulated by the outcomes of recent major storm events, there has been a growing interest in developing a more technically sound engineering approach to support the ‘mainstreaming’ of all types of NNBF into more comprehensive and sustainable flood defense systems (in conjunction with conventional flood defense systems). The U.S. Army Corps of Engineers is leading a collaborative project to develop international guidelines to inform the planning, design, construction, and operation or NNBF projects. Participants in the international team come from several countries and organizations including the United Kingdom and the Netherlands and include representatives from government, academia, and the private sector. This paper will describe the emerging issues and likely content of the guidelines including aspects such as guiding principles, design rules for more novel forms of NNBF, spatial upscaling of flow-slowing measures across catchments and adaptive management of NNBF measures

Creek systems in restored coastal wetlands: morphological evolution and design implications

Saltmarsh restoration such as managed realignment (MR) projects often include excavation of simplified tidal creek networks to improve drainage and marsh functioning, but their design is based on limited evidence. This paper compares the morphological evolution of creek networks in current MR projects in the UK with creek networks in natural saltmarshes, in order to provide improved guidance.The evolution of creek networks was monitored for 2–20 years post-breach at 10 MR sites across the UK by semi-automatically extracting 12 morphological creek parameters from lidar. The rates of creek evolution in MR sites are linked to the initial tidal, morphological and sedimentological conditions using principal component analysis, then compared with power law relationships of morphological equilibrium defined from 13 mature natural saltmarshes.MR creeks evolved into larger, more complex, better distributed systems, with a total creek length and volume statistically similar to their natural counterparts. However, the creek volume remains poorly distributed, with a mean distance between creeks ranging from 33 to 101 m versus 5–15 m for natural mature saltmarshes. MR creeks are also clustered around the breach area, leaving the marsh interior poorly drained. MR creek network morphologies remain strongly influenced by the initial creek template, as evidenced by unnaturally straight creeks inherited from former drainage ditches.A combination of external conditions (i.e., tidal range, sediment concentration in the wider estuary) and local conditions (i.e., site elevation, topographical heterogeneity, soil compaction) controls how easily creeks can form within MR sites. This in turn determines the amount of engineering effort required to help achieve reference site conditions. The end goal of creek design is to create MR sites that closely resemble reference site conditions, however the final design is also likely to be affected by a range of practical factors (e.g. engineering/cost) unique to each site and project

Appraising spit dynamics and estary responses: a coastal management study from the Exe Estuary, UK

The paper describes geomorphological analysis and morphodynamic modelling of the double spit enclosed Exe Estuary, UK. The long-term morphodynamic behaviour of the Exe Estuary system and the surrounding shoreline is studied. The geomorphological analysis was based on available historic data on the estuary. The morphodynamic modelling methodology is two-fold: A systems model based on a Boolean approach is used to predict and investigate future morphodynamic response of the estuary to changes in external forcing. A 1-line shoreline model is used to investigate morphodynamics of Dawlish Warren spit (the only active spit at the mouth of the estuary) and its future morphologies. It was found that over long term time scales, the estuary will reach a stable morphological state or evolve cyclically between two morphological states, depending on future changes to environmental forcing such as waves and tides. It was also found that littoral transport control has a significant effect on the long term sustainability of the Dawlish Warren sand spit and the estuary as a whole