Historical constraints on slope movement age: a case study at Broadway, United Kingdom

The Broadway area of the Cotswolds has been extensively investigated in an attempt to delineate areas of slope instability, including 'relict' landsli des, which may have been initiated under periglacial climatic conditions. I t is, therefore, useful both in terms of the geomorphology and of the under standing of the evolution of the area, to investigate the rates and timing of any reactivation and subsequent movements of landslides in this area. Th e remains of ridge and furrow cultivation can be seen extensively throughou t the Cotswolds. This particular agricultural practice, which documentary e vidence suggests dates back to Anglo-Saxon times (approximately 10th centur y AD), has been disturbed in many places by slope movements. A detailed stu dy of Parish Records and other local historical sources has revealed that r idge and furrow cultivation ceased on Parliamentary Enclosure, which in thi s area, occurred in 1771. Therefore, it is possible to identify patterns of slope movement between these dates. Landslides have been identified by gro und mapping and aerial photography, and can be divided into three categorie s. Firstly, active landslides which are those which have shown evidence of movement during the study period. Secondly, suspended landslides, which sho w evidence of movement, but have not been observed to move during the study period. In this context, this has been taken to mean landslides, which hav e shown evidence of movement since 1771. Thirdly, relict landslides which h ave shown no evidence of movement since 1771 and thus were probably active under a different climatic regime. By incorporating historical data with th e geomorphological survey it has been possible to identify areas of potenti ally difficult ground for engineering geomorphological purposes.