Monitoring mixed sand and gravel beaches using unmanned aerial systems

Mixed sand-gravel beaches act as an efficient natural sea defence and are increasingly managed by beach recharge, which can alter the sediment size composition of such beaches and their profile response. This creates an urgent need for better information about the behaviour of mixed sand and gravel beaches after recharge. UAS promise to be a promising novel tool in this context. To test their suitability for routine surveying, we aligned an experimental UAS survey along the standard monitoring schedule that was in operation for a mixed beach in East Sussex, UK. High wind speeds at the time of deployment significantly affected the data collection, but it was possible to generate (i) a surface model using Structure-from-Motion-based photogrammetry and (ii) an image mosaic that clearly identifies the spatial patterns of the sand-gravel mix of the beach. This indicates that UAS offer substantial potential for beach monitoring. However, an unclear legal framework acts and the sensitivity of platforms to high winds sets clear limits for UAS to serve as a stand-alone monitoring tool for beach environments at the present time

Chalk cliff retreat in East Sussex and Kent 1870s to 2001

The retreat of chalk cliffs fringing the eastern English Channel contributes shingle to the beaches which helps to protect the cliffs and slow down erosion. Conversely, cliff retreat endangers settlements and infrastructure on the clifftop. Rates of retreat have been calculated by a variety of methods over the past century, but no attempt has been made to provide a complete coverage that allows for a true comparison of retreat rates over the entire coastline. Using historic maps and recent orthophotos, cliff retreat rates have been calculated for consecutive 50 m sections of chalk cliff along the English side of the entire eastern English Channel for a period of 125 years. The chalk cliffs of East Sussex erode at an average rate of 0.25 - 0.3 m y−1 while those in Kent at a rate of 0.1 m y−1

Comparative beach surveys using an unmanned aerial system, ground-based GPS, terrestrial laser scanning, and airborne laser scanning

Profiles and sediment size distribution on mixed sand and gravel beaches are highly variable, both spatially and temporally, and cost-effective high-resolution monitoring schemes are needed to capture this variability. The potential for the use of UAS for coastal monitoring remains relatively untested in comparison to established remote sensing techniques. This paper reports on a field experiment in Pevensey Bay, East Sussex, England, in which simultaneous measurements were carried out using UAV-based photogrammetry, RTK-GPS, and both terrestrial and airborne laser scanning. The central objective of this research was to compare the accuracy of the TLS, ALS, and UAV-based surface modelling to draw conclusions for operational beach monitoring. The analysis was carried out through point cloud inter-comparison, comparison of point cloud performance against RTK-GPS transect data, and evaluation of differences between elevation models that were generated based on the point clouds. The point cloud comparison focused on the vertical differences between respective data sets, and showed that the UAV-based point cloud had positive offsets of 9cm (RMS 10cm) and 6cm (RMS 8cm) compared to the TLS and ALS point clouds, respectively. Analysis was also carried out to evaluate the extent to which surface sediment characteristics affected measurement accuracy of the different methods. Data comparison on beach gravel, beach sand, cobble, foreshore dry sand, foreshore wet sand and soft mud showed the best agreement between UAV, TLS and ALS data on gravel beach sections. For nearly all surface types UAV and ALS data showed better agreement than UAV to TLS data

Multivariate extreme value modelling of sea conditions around the coast of England

It is widely recognised that coastal flood events can arise from combinations of extreme waves and sea levels. For flood risk analysis and the design of coastal structures it is therefore necessary to assess the joint probability of the occurrence of these variables. Traditional methods have involved the application of joint probability contours, defined in terms of extremes of sea conditions that can, if applied without correction factors, lead to the underestimation of flood risk and under-design of coastal structures. This paper describes the application of a robust multivariate statistical model to analyse extreme offshore waves, wind and sea levels around the coast of England. The approach described here is risk based in that it seeks to define extremes of response variables directly, rather than the joint extremes of sea conditions. The output of the statistical model comprises a Monte Carlo simulation of extreme events. These distributions of extreme events have been transformed from offshore to nearshore using a statistical emulator of a wave transformation model. The resulting nearshore extreme sea condition distributions have the potential to be applied for a range of purposes. The application is demonstrated using two structures located on the south coast of England

The validation analysis of the INSHORE system: a precise and efficient coastal survey system

Government and environmental entities are becoming increasingly concerned with qualifying and quantifying the erosion effects that are observed in sandy shores. Correspondingly, survey methodologies that gather data for such erosion studies are increasingly being demanded. The responsible entities are continually broadening their areas of interest, are concerned in the establishment of regular monitoring programmes and are demanding high accuracy from the geo-spatial data that is collected. The budget available for such monitoring activities, however, does not parallel the trend in the increasing demand for quality specifications. Survey methodologies need improvement to meet these requirements. We have developed a new land-based survey system-the INSHORE system-that is ideal for low cost, highly efficient and highly precise coastal surveys. The INSHORE system uses hi-tech hardware that is based on high-grade global positioning system (GPS) receivers and a laser distance sensor combined with advanced software algorithms. This system enables the determination of the ground coordinates of the surveyed areas with a precision of 1 to 2 cm, without having a sensor in contact with the ground surface. The absence of physical contact with the ground makes this system suitable for high-efficiency surveys. The accuracy of the positioning, which is based on advanced differential GPS processing, is enhanced by considering the estimated attitude of the GPS receiver holding structure and eliminates undesirable offsets. This paper describes the INSHORE survey system and presents the results of validation tests that were performed in a sandy shore environment

The association between family and community social capital and health risk behaviours in young people: an integrative review

Background: Health risk behaviours known to result in poorer outcomes in adulthood are generally established in late childhood and adolescence. These ‘risky’ behaviours include smoking, alcohol and illicit drug use and sexual risk taking. While the role of social capital in the establishment of health risk behaviours in young people has been explored, to date, no attempt has been made to consolidate the evidence in the form of a review. Thus, this integrative review was undertaken to identify and synthesise research findings on the role and impact of family and community social capital on health risk behaviours in young people and provide a consolidated evidence base to inform multi-sectorial policy and practice.<p></p> Methods: Key electronic databases were searched (i.e. ASSIA, CINAHL, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Database of Abstracts of Reviews of Effects, Embase, Medline, PsycINFO, Sociological Abstracts) for relevant studies and this was complemented by hand searching. Inclusion/exclusion criteria were applied and data was extracted from the included studies. Heterogeneity in study design and the outcomes assessed precluded meta-analysis/meta-synthesis; the results are therefore presented in narrative form.<p></p> Results: Thirty-four papers satisfied the review inclusion criteria; most were cross-sectional surveys. The majority of the studies were conducted in North America (n=25), with three being conducted in the UK. Sample sizes ranged from 61 to 98,340. The synthesised evidence demonstrates that social capital is an important construct for understanding the establishment of health risk behaviours in young people. The different elements of family and community social capital varied in terms of their saliency within each behavioural domain, with positive parent–child relations, parental monitoring, religiosity and school quality being particularly important in reducing risk.<p></p> Conclusions: This review is the first to systematically synthesise research findings about the association between social capital and health risk behaviours in young people. While providing evidence that may inform the development of interventions framed around social capital, the review also highlights key areas where further research is required to provide a fuller account of the nature and role of social capital in influencing the uptake of health risk behaviours.<p></p&gt

Shared Agency with Parents for Educational Goals: Ethnic Differences and Implications for College Adjustment

This study proposed and confirmed three ways in which college students can perceive shared agency and two ways in which they can perceive non-shared agency with parents when pursuing educational goals in college. Differences and similarities were examined among participants from four ethnic backgrounds (N = 515; 67% female): East Asian American, Southeast Asian American, Filipino/Pacific Islander American, and European American. Results indicated that Asian American youth reported higher levels of non-shared agency with parents (i.e., parental directing and noninvolvement), lower levels of shared agency (i.e., parental accommodation, support, or collaboration), and poorer college adjustment compared to European Americans. However, ethnic similarities were found whereby perceived shared agency in education with parents was associated with college adjustment. Multiple mediation analyses also indicated that our model of shared and non-shared agency with parents explained differences in college adjustment between Asian and European Americans, though more strongly for comparisons between European and East Asian Americans. Our results suggest that parents continue to be important in the education of older youth but that continued directing of youth’s education in college can be maladaptive