Managed Realignment (MR) schemes are considered by many coastal managers and engineers to be a preferable method of coastal flood defence and compensating for habitat loss, by creating new areas of intertidal saltmarsh and mudflat habitat. Monitoring of MR sites has tended to focus on short term ecological factors, resulting in a shortage of high frequency, high resolution long term measurements of the evolution of the sediment erosion, transportation, deposition and consolidation cycle (ETDC) in newly breached sites. This is particularly true of analysis of the formation and preservation of sedimentary rhythmites and evaluations of sedimentation rates (and their variability) in newly inundated intertidal environments. This study provides an evaluation of sedimentation rhythms and hydrodynamics from two contrasting sites within the Medmerry Managed Realignment scheme, the largest open coast realignment in Europe (at the time of site inundation). Bed sediment altimeter data highlighted different sedimentation patterns at the two sites; near constant deposition of sediment occurred near the breach resulting in 15.2 cm of sediment being accreted over the one year monitoring period, whereas periodic accretion and erosion of sediment occurred inland leading to 2.7 cm of net accretion. Differences in the relationship between suspended sediment concentrations and site hydrodynamics were observed on a semi-diurnal to annual scale. This study highlights the need for further consideration of the sedimentation processes in MR schemes in order to enhance the design and construction of these sites. Advancements in the understanding of these processes will increase the success of MR schemes in terms of the evolution of the sediment regime and the ecosystem services provided, particularly as they are more widely accepted as a form of coastal flood defence and intertidal habitat creation method.

Coastal and estuarine wetlands provide a range of important ecosystem services, but are currently being damaged and degraded due to human activities, reduced sediment supply and sea level rise. Managed realignment (MR) is one approach used to compensate for the loss of intertidal habitat, however saltmarshes in MR sites have been recognised to have lower biodiversity than natural environments. This has been associated with differences in the physical functioning including the sediment structure, reduced hydraulic connectivity, and lower topographic variability such as the abundance of intertidal creek networks. Intertidal morphology, including creek networks, play an important role in supporting and regulating saltmarsh environments through the supply of sediment, nutrients and water, and in draining intertidal marshes. However, there is a lack of empirical data on the formation and evolution of topographic features and variability in saltmarsh environments. This is likely to be due to creek networks in natural marshes already being in a state of quasi-equilibrium, making MR sites an ideal environment to investigate creek development. However, traditional remote sensing techniques (such as LiDAR) tend to be relatively expensive, infrequent and at a coarse resolution meaning small, but important (cm-scale), changes are often missed. This study advances the ability to detect these small scale changes by demonstrating the suitability and potential applications of using the emerging photogrammetric method Structure-from-Motion (SfM) on images taken using a small-Unmanned Aerial System (sUAS). Three surveys from a rapidly changing, near-breach site were taken at the Medmerry Managed Realignment Site in July 2016, September 2017 and July 2018. A suitable degree of confidence was found between the modelled surface and independent check points (vertical root-mean-square-errors of 0.0245, 0.0704 and 0.1571 for 2016, 2017 and 2018 respectively). DSMs of Difference (DoD) analysis was performed to evaluate elevation change, with areas experiencing up to 85 cm of accretion between 2016 and 2018. However, when considering the error associated with both surveys, between 2016 and 2017, only 34.39 % of the survey area experienced change above the level of detection (LoD). In contrast, 76.97 % experienced change greater than the LoD between 2017 and 2018. Stream order analysis classified the creek networks into five orders in 2016 and four orders in 2017 and 2018, with 2016 having a higher abundance (291 in 2016 compared to 117 (2017) and 112 (2018)) and density (0.44 m/m 2 in 2016 compared to 0.27 m/m 2 in both 2017 and 2018) of creek networks. These results provide an innovative high resolution insight into the evolution of restored intertidal wetlands, and suggest that SfM analysis of images taken using a sUAS can be a useful tool with the potential to be incorporated into studies of MR and natural saltmarsh sites. sUAS analysis can, therefore, advance the management of these environments to ensure the provision of ecosystem se...

Accelerated low water corrosion is a form of marine steel corrosion caused by bacterial activity. It has a global spread and is potentially responsible for billions of pounds of damage. We have determined in detail both the chemistry of corrosion products and the associated microbiology at a UK site. The corrosion products form a layered structure with iron sulfides at the steel surface and iron oxides and sulfates in contact with water. The iron sulfides are formed by reaction of steel with hydrogen sulfide formed by sulfate-reducing bacteria and are oxidised through a series of sulfur oxidation states by sulfide-oxidising bacteria, forming acid at all stages and encompassing the whole of the bacterial sulfur cycle. The bacteria involved are endemic in anoxic bed sediment, and the process is a response to the presence of steel as an electron donor, and the generation of anoxic microenvironments within corrosion products.

Managed realignment (MR) schemes are being implemented to compensate for the degradation of coastal habitats. However, evidence suggests that MR sites have lower biodiversity than anticipated, which has been linked to poor drainage. Despite creek networks playing an important role in enhancing site drainage in natural intertidal environments, there remains a shortage of data on the formation and evolution of creeks within MR sites. This study evaluates creek development at the Medmerry Managed Realignment Site, UK. Creek development is investigated using differential global positioning system (dGPS) data, supported by sedimentological analyses and a high-resolution digital surface model (DSM) derived from images taken using a small unmanned aerial vehicle. Measurements indicated that creeks will develop relatively quickly, but are influenced by differences in the sub-surface sedimentological conditions. A suitable level of agreement was found between the DSM and dGPS measurements, demonstrating the appropriateness of this method to study creek development within intertidal environments at a higher resolution than traditional surveying techniques. These results are used to propose the collapse of sub-surface piping as the primary creek formation mechanism. Findings are discussed in terms of increasing the success of MR schemes and enhancing site design to maximise the ecosystem services provided.

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