The use of ERDDAP in a self-monitoring and nowcast hazard alerting coastal flood system

<div> <p>In the UK, £150bn of assets and 4 million people are at risk from coastal flooding. With reductions in public funding, rising sea levels and changing storm conditions, cost-effective and accurate early warning flood forecasting systems are required. However, numerical tools currently used to estimate wave overtopping are based on tank experiments and very limited previous field measurements of total overtopping volumes only. Furthermore, the setting of tolerable hazard thresholds in flood forecasting models requires site-specific information of wave overtopping during storms of varying severity. </p> </div><div> <p>The National Oceanography Centre (NOC) are currently developing a new nowcast wave overtopping alert system that can be deployed in site-specific coastal settings to detect potentially dangerous flood conditions in near real-time (NRT) while validating operational forecasting services. At its core, it utilises a prototype overtopping sensor and an instance of the National Oceanic and Atmospheric Administration’s ERDDAP data server in a self-monitoring and alerting control system. In-situ detection will be performed by WireWall, a novel capacitance wire sensor that measures at the high (400 Hz) frequencies required to obtain the distribution of overtopping volume and horizontal velocity on a wave-by-wave basis. The sensor includes on-board data processing and 2-way telemetry to enable automation and control. The telemetry posts regular health summaries and high-resolution (1 sec) hazard data (produced by the on-board processing) using the standard internet protocol (https) to an open ERDDAP server so data are freely available via an application programming interface (API) alongside other NRT and delayed-mode global coastal ocean and weather information for further data exploration. ERDDAP allows NRT hazard data to be accessed by statistical algorithms and visual applications, as well as receiving alerts that are also fed to messaging queue points (RabbitMQ) that can be monitored by external systems. Combined, this will enable automated health monitoring and sensor operation as well as offer the potential for downstream hazard management tools (such as navigation systems and transport management systems) to ingest the nowcast wave overtopping hazard data. To integrate data with wider systems and different disciplines, ERDDAP data sets will be enriched with common and well-structured metadata. Data provenance, controlled vocabularies, Quality Control and attribution information embedded in the data workflow is fundamental to ensuring user trust in the data and any products generated, while enhancing FAIR data principles. </p> </div><div> <p>The new nowcast wave overtopping alert system will be tested in 2021 during field deployments of multiple WireWall systems at two high energy coastal sites in the UK. Such data are crucial for validating operational flood forecast services as well as protecting local communities and minimising transport service disruptions. The addition of SMART monitoring optimises sensor maintenance and operation, reducing the costs associated with teams travelling to the site. Using ERDDAP embedded with well-structured metadata enables machines to access multiple flood parameters through a single point that abstracts users from the complexities associated with the source data, offering the potential for further data exploration through modelling or techniques such as machine learning. </p> </div>