In recent years, there has been a trend towards using the behavioural properties of materials, especially soils, to explain geomorphological features. Good examples can be found in Carson and Kirkby (1972), Carson (1971a), Whalley (1976) and Statham (1977). In this section, various ways of investigation of these strength parameters will be examined. The techniques discussed here relate directly to Part Four, especially to slope processes. The methods are primarily for use in the laboratory but some are suitable for field use and require inexpensive equipment. For further reading, the books by Akroyd (1969), Bishop and Henkel (1962), Smith (1978), British Standards Institution (1975c) (BS 1377) and Vickers (1978) should be consulted.