Modelling Hazards to the Historic Environment: Ex-Hurricane Ophelia and Mellor

StormAdmin News

As the STORM project is now well into its second year the design of the experimental hardware and software systems that will be used to predict hazards to Cultural Heritage sites and co-ordinate the response to any damage from these hazard events has progressed to the detailed design and individual element testing stages. Broadly, these threats fall into long term and acute hazards, whilst the responses to these are roughly split between rapid emergency reactions and long-term avoidance strategies. A variety of hazard scenarios are currently being tested at the project pilot sites.

At the UK pilot site in Mellor, Stockport, one part of the experimental warning systems is already being tested in real time. This aspect of the project is the gathering and use of weather data from the three weather stations located in the Mellor landscape and the observation of the impact of weather events on the Cultural Heritage of this particular pilot site. Each of the five pilots’ sites have their own unique hazards. Mellor in the UK is the only pilot site, for instance, where there are multi-period below-ground archaeological remains in an upland context at three separate locations: Oldknows Mill in a valley location at c. 90m AOD; the Iron Age hillfort at Mellor Old Vicarage at c. 220m AOD; and the Bronze Age cairn on Mellor Moor at c. 324m AOD.

The approach of ex-hurricane Ophelia in mid-October provided an opportunity to track its real-time impact on these three archaeological sites and then to observe any damage immediately afterwards with a view to helping refine both the hardware and software elements of this part of the STORM project. Ophelia is notable as being the most-easterly recorded Category 3 Hurricane in the Atlantic. It made landfall in the Irish Republic and the UK as an area of stormy low pressure on October 16th. The Mellor pilot site lay on the eastern edge of the storm’s course, but even so our three weather stations record steadily increasing wind speeds and gusts from around 3am to a peak in intensity around 8pm.

Two forms of interfaces were used. The first, courtesy of the WeatherLink Network, provided a timed snapshot of the weather conditions noting the daily accumulation of rain, temperature highs and the highest wind speeds (Fig 1). The second, using the Weather Underground platform (Fig 2), provided both a timed snapshot of data as well as graphs showing trends through a 24 hour period. For non-weather specialists seeking to understand how a weather event was developing at a specific location the Weather Underground platform was the easiest to read, also allowing some more detailed interrogation of the data. Thus, one notable feature of the storm was the lack of any significant rainfall, whilst wind speeds peaked at around 60km/h with gusts above 100 km/h. This kind of user-friendly approach might be considered for the final STORM hazard-warning platform.

A visual inspection of all three sites on the morning of the 18th October revealed no significant damage at either Oldknows Mill, the hillfort at the Mellor Vicarage, nor at Shaw Cairn on Mellor Moor. Although there was debris on the floor (branches, leaves, and twigs) none of the sites had any visible damage. Significantly, the weather stations remained intact and functional (Fig 3). Furthermore, the active management of the woodland around the Oldknows Mill site since 2012 was probably a significant factor in reducing the danger of falling branches and trees during the storm.

The STORM project continues to develop and test a variety of climate- and human-related hazard scenarios, which is why a real-time weather scenario such as ex-hurricane Ophelia is important in testing both the robustness of the hardware on site and the usability of the software in hazard mapping. No doubt there will be an opportunity to track a severe rain event over the winter at Mellor and then add that experience to the scenarios we are modelling.

[Text Box: Fig 1: The WeatherLink Network interface showing data for Mellor Mill at 16.45 BST, October 16, 2017.]