Scour hole development in river beds with mixed sand-clay-peat stratigraphy

Huismans, Y. and van Velzen, G. and O’Mahoney, T. and Hoffmans, G. and Wiersma, A. (2016) Scour hole development in river beds with mixed sand-clay-peat stratigraphy. In: ICSE 2016 (8th International Conference on Scour and Erosion), 12-15 September 2016, Oxford, UK.

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Abstract

River deltas are often characterized by a heterogeneous subsoil stratigraphy, composed of layers of sand, clay and peat. This has important consequences for the riverbed morphology and in particular the formation of scour holes. When the riverbed is composed of poorly erodible clay or peat, erosion processes are retarded. However, when thinner parts of clay or peat layers erode; underlying sand patches are incised and large scour holes may develop within in a short amount of time. The unpredictability and fast development makes these scour holes difficult to manage while stability of dikes and infrastructure may be at stake. In this paper we study the scour hole formation and development in heterogeneous subsoil. The Rhine-Meuse estuary forms the ideal system for this analysis as it has been intensively measured and contains about 100 scour holes. Based on nearly 60 years of river bed topography data and data on the subsurface lithography and hydrodynamics, we present a system analysis of scour hole formation in heterogeneous subsoil stratigraphy. In addition the detailed growth of a recently formed scour hole is studied and compared to scale model tests.

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