The current valley upsidence and closure prediction methods were first published in 2002, following completion of ACARP Research Projects C8005 and C9067. These methods use conservative empirical prediction curves, which were drawn above all of the observed upsidence and closure data. The data was extracted from subsidence surveys that had been carried out in valleys at most of the collieries in the Southern Coalfield. Little site-specific surface geological data was available at that time for the monitored valley sites and the considerable scatter that existed under the prediction curves indicated that many factors probably influenced the extent of the upsidence and closure movements.
Extensive monitoring has been carried out in valleys since 2002 and the observed upsidence and closure movements have shown that the current methods for predicting upsidence and closure movements are predominantly conservative. Reviews of the few exceedance cases have indicated that various local geology and landform factors at these monitored sites may have also influenced the magnitude of the observed upsidence or closure movements.