At least two Formby Ordnance Survey benchmarks still survive today, despite being obsolete and abandoned by the O.S.
Following the start of the controversy about the proposed building development in Formby I have been wondering about the height of the land for the proposed development. I looked for and found two O.S benchmarks. There are probably still more in Formby. They were significant because they were used to establish the height of building foundations against a known recorded data point.
The Ordnance Survey Bench marks (BMs) are survey marks made by Ordnance Survey to record height above Ordnance Datum. If the exact height of one BM is known then the exact height of the next can be found by measuring the difference in heights, through a process of spirit levelling.
Most commonly, the BMs are found on buildings or other semi-permanent features. Although the main network is no longer being updated, the record is still in existence and the markers will remain until they are eventually destroyed by redevelopment or erosion.
You can also find web based tools that do the same. For instance according to one web site the height of the proposed Housing Development off Liverpool Road varies between 5 and 6 metres above sea level.
The land is known to be prone to surface water flooding, it's called Fluvial Water Flooding by the Environment Agency. All their future plans assume that this type of flooding will increase with the advent of further Climate Change. The limited height above sea level will surely pose a significant challenge to any development of the site.
What do you think?