Slope instability within a residential area in Cleveland, UK

Abstract

Purpose of survey An integrated geomorphological survey involving detailed geomorphological field mapping and associated desk studies is a powerful tool in identifying the locations and nature of slope instability within built-up areas. When supplemented with existing or specifically designed ground investigation, initial instability processes and mechanism models can be re-evaluated and refined. This paper provides an example of a geomorphological survey at Yarm, County Cleveland, which aimed to delineate unstable areas and address the potential causes of ground movements within a residential area. The site Valley Drive and Denevale are situated at the far eastern end of Yarm, on the south side of the River Tees, near its confluence with the River Leven. The natural valley side slopes are about 10–15° in this area and rise up towards a plateau surface at 30 m A.O.D., some 20–25 m above the Tees Valley. In order to facilitate development on the valley side slopes, extensive cut and fill operations have been carried out. Artificial slopes steepened up to 37° and vertical walls to 3 m high were also evident. The published 1:10 560 scale British Geological Survey map (1976) and the 1:50 000 scale British Geological Survey map (1987) indicate Triassic Sherwood Standstone formation (formerly ‘Bunter– Sandstone) as outcropping within the river channel. The valley side slopes have been developed in thick superficial deposits which comprise Upper and Lower Glacial Till units, separated by Glacial Sands and Gravels overlying Laminated Clay. These materials are believed to have been deposited during the