Engineering geomorphological input to ground models: an approach based on Earth systems

Abstract

The engineering geomorphological input to ground (‘geo’) models as part of standard site investigations tends to lack a systematic approach and is often restricted only to morphological mapping, the naming of landform features and usage of outdated morphoclimatic concepts. Ground models require more sophisticated geomorphological approaches and this is particularly apparent in regions such as Europe and North America where ground conditions can be strongly influenced by geomorphological processes linked to Quaternary or older environmental changes. Within this paper it is proposed that an ‘Earth system science’ approach underpinned by the ‘rock cycle’ can provide a framework for a systematic and more detailed geomorphological input into ground models. Such a framework lends itself to recognizing the fact that landscapes comprise multiple ‘fragments’ of process–response landforms, which, under contemporary conditions, may be: relict and inactive; relict but reactivated; subject to change once certain threshold events occur; or fully active. Using the rock cycle, a simple basis for landform categorization is outlined starting with a four-fold subdivision into structural, weathering, erosional and depositional landforms that allows the user to focus initially on the historical development of the landscape. Each category comprises a system of landforms that occur over standard geomorphological scales (pico-, nano-, micro-, meso-, macro- and mega-scale) as part of a process–response system. Macro-scale landforms are readily identifiable within a landscape, typically occurring as six principal terrain types: hills, ridges, mountains, plains, valleys and basins. These in turn comprise a series of meso-scale features that, once identified, can inform about the geomorphological processes that have resulted in their formation. The geomorphological input into ground models benefits primarily from recognition of these meso-scale landforms and the processes responsible for their formation, although smaller-scale landforms may have importance for specific engineering structures.