Engineering Geomorphological Mapping
“Whilst engineering geological mapping is concerned with the properties of materials and their immediate or short term engineering implications, geomorphological mapping takes in a greater sweep of time, combining the recent geological past with present geomorphology and its foreseeable future. Integration of the two approaches combines the short term static with the longer dynamism of the landscape”
Hearn, G. 2002. Engineering geomorphological mapping for road design in unstable mountainous areas: lessons learnt after 25 years in Nepal. Quarterly Journal of Engineering Geology Vol 35 pp143-154.
An understanding of landscape evolution is fundamental to most engineering geological assessments, but in particular to landslide hazard assessments. Some basic geomorphological concepts which underpin this are:
- A given set environmental conditions and constant processes over time produce a set of characteristic landforms
- The landscape rarely reflects any one climate or period of change, they are palimpsests of superimposed histories i.e. a mosaic of landscape features of different age and origins
- The pattern of historical and future landsliding will reflect one or more modes of landscape change
- Landslides features have a finite lifetime within the landscape
- Landslide activity can be characterised by 2 contradictory factors (a complex and uncertain sequence of events, often with variable time periods; and the establishment and maintenance of a characteristic set of landforms which persist through time) which form a fundamental problem for prediction.
Hazard assessments need to consider all timescales to develop a reliable assessment of risk. Many however only focus only on high frequency low magnitude events, hence an understanding of engineering geomorphology is fundamental to appropriate hazard and risk assessments.
Sewell, R. J., Parry S, Millis S. W., Wang N., U. Rieser U. &. DeWitt R. (2015) Dating of debris flow fan complexes from Lantau Island, Hong Kong, China: The potential relationship between landslide activity and climate change. Geomorphology 248 205 –227.
Parry, S. & Hart, J. R. (2012). Engineering geomorphological mapping for landslide hazard assessments in Hong Kong. Proceedings of the 11th International Symposium on Landslides (ISL) and the 2nd North American Symposium on Landslides.
Parry, S. (2011). The Application of Geomorphological Mapping in the Assessment of Landslide Hazards in Hong Kong. Chapter 15 in Developments in Earth Surface Processes, Volume 15, Geomorphological Mapping; Methods and Applications, Edited by M. J. Smith, P. Paron & J. S. Griffiths. Elsiver.