Coastal monitoring and historical change : techniques and technologies report

A common and urgent challenge facing coastal communities in England and Wales is the risk of coastal erosion and flooding. To help coastal communities adapt and become more resilient to these risks, and to better inform future change, there is a need to understand historical coastal change. Coastal change is understood here as change affecting three main realms: the natural environment, the built environment and coastal communities.
For each realm, the concept of coastal change is different and therefore the techniques and technologies used to monitor historical change will also differ. Change to the natural environment due to coastal erosion and flooding is described as any permanent physical change to the shoreline caused by erosion, landslide, permanent inundation (flooding) or coastal accretion. These physical changes also represent change to natural capital, the natural resources that provide ecosystem services. Changes to the built environment are understood as any modification to the number and footprint of residential properties, non-residential properties, community services, public spaces, utilities, infrastructure (e.g. septic tanks, caravans, rail, road, runways) and cultural heritage sites. Finally, changes in coastal communities are understood here as changes in the characteristics of the at-risk population and their resilience and access to resources which could offset the effects of coastal erosion and flooding hazards.
With a few exceptions, like the Coastal Zone Mapping Project (CZM) sponsored by the UK Geospatial Commission, previous research and evidence of techniques and technologies to monitor historical coastal change in England and Wales exists in different places, often as grey literature that is scattered and not synthesised. A better understanding of what techniques and technologies have been used in the past and could be used in the future to monitor coastal change in all three realms (natural environment, built environment and coastal communities) is relevant to several initiatives related to policy and ongoing monitoring efforts. The aim of this project was to review and summarise the various coastal monitoring techniques and technologies that are available to document historical coastal change and outline the most appropriate data collection methodologies that can systematically and routinely assess both historical and contemporaneous coastal change of the natural environment, built environment and coastal communities.
The minimum list of techniques and technologies included in this process were defined at the outset of the project as listed below:
• Historic maps and charts
• LiDAR and other 3D surveys
• Aerial photography and 2D surveys
• Satellite imagery
• Topographic surveys
• Bathymetric surveys
• Terrestrial ecological mapping
• Hydrodynamics
Local Authority Reports
The results presented here were obtained mostly by a process of workshop consultations and synthesis with relevant coastal change data users (end-users) and coastal change data providers (service providers) and supported by the Defra “FD2724 Coastal Monitoring and Historical Coastal change: Rapid Evidence Assessment” report.
A clear outcome of this project is the body of implications of the inevitable methodological differences and changes over time in the way that shoreline position, land use and community awareness are measured. These differences have important implications for analyses of historic data in all three realms (natural environment, built environment and community awareness) for retrospective analyses of old data or for quantifying changes over time. Any such analyses need to consider how to overcome observer variations, changes in recording methods or technologies and their impacts on what the reported indicator means in their widest sense.
◼ For Shoreline Change Analysis, the definition of shoreline varies considerably depending on the scale and purpose of the study, but it is a term that generally refers to the interface between land and sea. Despite the apparent simplicity of this, in practice it is a challenge to apply consistently.
◼ When measuring changes on land use, (Comber et al., 2016) suggested adopting the mind-set of the original mapper and accept the original boundaries between thematic classes where possible, to consider the concepts underneath the class labels driven by measurement and changes in survey objectives and to flag any inconsistences or errors in the original data when they are suspected.
◼ Creating awareness of historical coastal change will trigger different emotions from different people based on their own memories and experiences.