Impact case study database

The importance of rock lighthouses for safe marine navigation grows with world trade. The most recent World Bank data show this growth as Twenty-foot Equivalent (container) Unit (TEU) traffic rising from 560 million in 2010 to over 790 million in 2018 ( https://data.worldbank.org/indicator/IS.SHP.GOOD.TU), much of it accommodated by an increased merchant fleet. As an island trading nation experiencing some of the world’s strongest storms, the UK is particularly vulnerable to maritime navigation failure; the loss of one strategic lighthouse will have incalculable effects on safety and trade. The GLA maintenance programmes for rock lighthouses have previously been limited to visual inspections, repairs of obvious damage and weatherproofing. UoP research has provided a more systematic approach to long-term survivability, which was beyond the capability of the GLAs.

Guidelines on storm waves for international navigation authorities

The UoP STORMLAMP project has resulted in the development of guidance documents for the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) which includes authorities in the US China, Russia, Brazil, India, South Africa, and Australia. The national members of the IALA are legally responsible for aids to navigation (AtoNs), e.g. lighthouses and buoys. Raby’s findings on environmental loading of heritage structures [ 5.1] led to an invitation to contribute to the IALA Engineering Committee Working Group 2 (Technical Knowledge and Sustainability). This committee prepares and reviews guidance on technical matters and monitors specific developments of issues relating to navigation aids, working in cooperation with International Organization for Standardization (ISO).  Following the October 2020 meeting, approaches developed in the STORMLAMP project are cited in the draft IALA Guideline: Extreme Environmental Conditions that identifies appropriate standards for AtoN equipment. Although available for day-to-day use already, as per standard IALA working practices this draft guideline will be formally adopted, after the consultation period, as a full guideline focusing particularly on wave loading and structural response, using the STORMLAMP project as its base; the next committee session will start in 2022. Other key contributors will include the Australian organisation AMS Group, the Korea Institute of Aids to Navigation, and Armada de Chile Directemar. These guidelines ensure that mariners have aids to navigation which meet their needs, both now and in the future, thus, contributing to a reduction of marine accidents and increased safety of life and property at sea [5.2].   The report of the 12^th session of the IALA ATON Engineering and sustainability committee 30/9-16/10 2020 noted that “Alison Raby made a significant contribution on wave impact on rock lighthouses” and in his testimonial IALA’s Deputy Secretary-General & Dean comments that: “The outcome of the study has now been incorporated into a revised Guideline titled “AtoN equipment and structures exposed to extreme environmental conditions”… the Guideline describes the approaches developed in the STORMLAMP project and the project outcomes.  [This]… will be part of the many guidelines available internationally for reference by AtoN maintainers and Authorities.” And goes on to say “The unique and ground breaking research of Professor Raby and her team has increased our understanding of the behaviour of lighthouses in the stress of the sea, our understanding of their long term viability and enabled the organisation to revise guidelines which will inform practice in the sector. This is a specialised field and we are grateful for the knowledge gained and shared by this study which will be used by International AtoN authorities and maintainers in order to keep their AtoN estate in good and safe order for the future.”

Guidelines on rock lighthouse monitoring and modelling

The STORMLAMP findings have also been incorporated into a Guidance Note for the UK & Irish GLAs: Wave Loading on Rock Lighthouses - STORMLAMP project techniques and findings [5.3]. This includes more comprehensive information than is included in the current IALA guidelines. It was developed iteratively with the GLAs to ensure an appropriate form for utilisation by their engineers.  In his comments to the final workshop of the STORMLAMP project Trinity House’s Director of Operations stated [5.4]: “…it [STORMLAMP] has proven to be of great value. As a result there is now far greater understanding of the behavior of our structures especially in the sort of extreme wave loading conditions which may be more prevalent in the future with the impact of climate change.”

Ensuring safe operating conditions for maintenance teams

Our research has informed procedures for monitoring lighthouse behaviour and periodic onsite surveys for the Trinity House rock lighthouses [5.5].  These lighthouses are no longer manned but remain an important part of safe navigation with automated lights and remote monitoring. This modern approach to usage of legacy structures has introduced several new challenges. STORMLAMP data has been used to assure maintenance teams of safe operating conditions and helps inform planning for safe maintenance schedules. In addition, STORMLAMP modelling work has provided crucial details for how to undertake more focused inspections of the existing helidecks; how to retrofit and redesign helidecks which are now at the end of their design life and how to design the next generation of helideck structures. We have also provided a break-through in minimal monitoring of inaccessible structures. Systems have been developed for low cost, low-power (hence low-carbon), long-lived instrumentation for structural vibrations and to potentially provide video evidence of damage to helideck structures, solar photovoltaic panels, and lantern glazing following storms. This will reduce helicopter visual checks with associated economic (£3,000 / hour for helicopter flights) and CO₂ savings (~0.2 tonnes per 20 minute flight with required 1 hour positioning¹). In his testimonial, the Northern Lighthouse Board’s Asset Manager stated: “…provision of equations to enable us to conduct limit state analysis of all our rock stations. This tool effectively allows us to do an overall structural stability calculation for all of our assets, potentially savings thousands of pounds in consultancy surveys and services. Having this information allows us to operate safely into the future, with our team’s confidence in the lighthouse conditions and mariners assured of an everlasting navigational beacon” [5.6].

Reassurance on structural safety

As climate change causes rises in sea level, the impact of wave loading on the Fastnet lighthouse was causing concern about its survivability in an increasingly hostile environment. Our research reassured the Commissioners of Irish Lights that Fastnet is in no danger from rising sea levels for at least the next 50 years.  This reassurance enabled savings, both in terms of cost (helicopter and staff) and CO₂ output (numerical indicators given in the above example) accrued from reductions in detailed assessments or far more costly intervention if the structure was thought to be at risk. This insight could not have been delivered by a commercial engineering consultancy company due to the comprehensive nature of the investigation and the use of sophisticated analysis methods. In his testimonial the Operations and Property Manager, of the Commissioners of Irish Lights [5.7] stated: “The overall assessment from the STORMLAMP project is that the stability of the Fastnet lighthouse, in its current condition, gives no cause for concern with the sheer mass of the lighthouse and its interconnected masonry construction capable of withstanding the worst of the Atlantic storms and the predicted increases in sea levels and wave impacts arising from climate change effects. We are also very pleased to be associated with results that will be disseminated via the International Association of Lighthouse Authorities (IALA) and be used as guidance for other light authorities facing similar challenges. We have a role in global aids to navigation best practice and are pleased that this work has demonstrated for the first time anywhere in the world how modern science can help us mange heritage structures.”

Our baseline data from the modal testing of Dubh Artach, one of the Northern Lighthouse Board (NLB)’s rock lighthouses situated off the west coast of Scotland, is of great value to that authority. Source 5.7 states: “…particular aspects that will inform our operations now and into the future… [the] concept of a simple, low-cost monitoring system for our lighthouses that will enable us to remotely monitor their structural behaviour, and compare with baseline data to see if the structural response changes, indicating damage not discernible to the naked eye allowing appropriate early intervention”. Future sea level rise associated with climate change could cause breakage to the interlocking blocks in the tower. The NLB will be able to compare the baseline data with data obtained from simple (user friendly) equipment for long-term monitoring of the lighthouse during winter months. Any change will indicate that damage has occurred; this may not have been apparent otherwise [5.8].

STORMLAMP also resulted in assurance and economic savings for the EA [5.9]. The EA has £5.2 Billion to spend on Flood and Coastal Erosion defences for the period 2021 - 2027; much of this will involve repair and rehabilitation of existing masonry structures subject to chronic and acute wave loading. Through their engagement with the project they have gained insight into the modelling response of masonry structures to wave loading, specifically, the Portreath harbour wall which underwent repair work following storm damage in 2018. Finite Element modelling as part of our project verified that the new structure will not fail under the same wave loading that caused the recent damage: “…the techniques considered and applied and the learning and guidance provided will undoubtedly help us better understand the management of maritime masonry assets and plan for the maintenance and their management going forward.” The Environment Agency’s National Coastal Manager.