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.

Morphological evolution of creek networks in 10 restored coastal wetlands in the UK.

Coastal wetlands provide crucial ecosystem services including flood protection and carbon storage, but are being lost rapidly worldwide to the combined effects of sea-level rise, erosion and coastal urbanisation. Managed Realignment (MR) aims to mitigate for these losses by restoring reclaimed land to tidal influence. Data of creek evolution is critical to assess the performance of design strategies and improve design and implementation practices. This data descriptor provides a dataset of the horizontal morphological evolution of creek systems from various initial conditions in 10 MR schemes across the UK. Using a semi-automated workflow, morphological creek parameters were extracted from 52 lidar datasets at 1 m horizontal resolution spanning 2 to 20 years post-breach. This constitutes the most comprehensive systematic monitoring of MR creek morphology to date. The dataset will assist future MR design and provide baseline morphological information for ecological and biogeochemical surveying.

Operationalising coastal resilience to flood and erosion hazard: A demonstration for England.

Resilience is widely seen as an important attribute of coastal systems and, as a concept, is increasingly prominent in policy documents. However, there are conflicting ideas on what constitutes resilience and its operationalisation as an overarching principle of coastal management remains limited. In this paper, we show how resilience to coastal flood and erosion hazard could be measured and applied within policy processes, using England as a case study. We define resilience pragmatically, integrating what is presently a disparate set of policy objectives for coastal areas. Our definition uses the concepts of resistance, recovery and adaptation, to consider how the economic, social and environmental dimensions of coastal systems respond to change. We develop a set of composite indicators for each dimension, grounded empirically with reference to national geospatial datasets. A prototype Coastal Resilience Model (CRM) has been developed, which combines the dimensions and generates a quantitative resilience index. We apply it to England's coastal hazard zone, capturing a range of different stakeholder perspectives using relative indicator weightings. The illustrative results demonstrate the practicality of formalising and quantifying resilience. To re-focus national policy around the stated desire of enhancing resilience to coastal flooding and erosion would require firm commitment from government to monitor progress towards resilience, requiring extension of the present risk-based approach, and a consensus methodology in which multiple (and sometimes conflicting) stakeholder values are explicitly considered. Such a transition may also challenge existing governance arrangements at national and local levels, requiring incentives for coastal managers to engage with and apply this new approach, more departmental integration and inter-agency cooperation. The proposed Coastal Resilience Model, with the tools to support planning and measure progress, has the potential to help enable this transition.

An approach for the identification of exemplar sites for scaling up targeted field observations of benthic biogeochemistry in heterogeneous environments.

Continental shelf sediments are globally important for biogeochemical activity. Quantification of shelf-scale stocks and fluxes of carbon and nutrients requires the extrapolation of observations made at limited points in space and time. The procedure for selecting exemplar sites to form the basis of this up-scaling is discussed in relation to a UK-funded research programme investigating biogeochemistry in shelf seas. A three-step selection process is proposed in which (1) a target area representative of UK shelf sediment heterogeneity is selected, (2) the target area is assessed for spatial heterogeneity in sediment and habitat type, bed and water column structure and hydrodynamic forcing, and (3) study sites are selected within this target area encompassing the range of spatial heterogeneity required to address key scientific questions regarding shelf scale biogeochemistry, and minimise confounding variables. This led to the selection of four sites within the Celtic Sea that are significantly different in terms of their sediment, bed structure, and macrofaunal, meiofaunal and microbial community structures and diversity, but have minimal variations in water depth, tidal and wave magnitudes and directions, temperature and salinity. They form the basis of a research cruise programme of observation, sampling and experimentation encompassing the spring bloom cycle. Typical variation in key biogeochemical, sediment, biological and hydrodynamic parameters over a pre to post bloom period are presented, with a discussion of anthropogenic influences in the region. This methodology ensures the best likelihood of site-specific work being useful for up-scaling activities, increasing our understanding of benthic biogeochemistry at the UK-shelf scale.

A comparison of surface features on submerged and non-submerged bone using scanning electron microscopy.

Skeletal remains are excellent sources of information regarding the deceased individual and the taphonomic history of their body. However, the accuracy of this information is governed by our ability to interpret features on the surface of a bone. Little research in this respect has been carried out on remains found in aquatic environments. This study compares damage features created on the surface of modern and archaeological bone found in a seawater environment, to surface features present on unmodified bone, archaeological bone, pathological bone and burned bone. Results show that no similarities with regard to surface pores were identified between submerged modern bone and archaeological, pathological and burned bone. Similarities were seen between submerged and dry archaeological bones. Thus it is argued that the misinterpretation of the taphonomic history of isolated bones recovered from bodies of water should be avoidable in the forensic context.