Geoscience Reference
In-Depth Information
Application of a Videometric Measurement
System to Investigate Spatial Dike Breach
Lukas Schmocker
1
Introduction
1.1 Dike Erosion
The main causes of dike breaches are overtopping, internal erosion (piping) or loss
of stability, yet most earth dikes fail due to overtopping as they are not designed to
resist overflow and their resistance to failure caused by surface erosion is limited
(Singh 1996 ). Dike overtopping starts normally at the lowest crest elevation or at a
local dike discontinuity, e.g., at a bridge abutment. If water runs over the downstream
dike slope, excessive surface shear stresses initiate the erosion process. Erosion starts
if the induced shear stress exceeds the critical shear stress of the dike material. Once
the initial breach is formed, the erosion process may be either plane or spatial. The
latter case normally occurs in nature and includes both vertical and lateral erosion.
1.2 Research in the Past
Plane dike erosion has been investigated by, e.g., Powledge et al. ( 1989a , b ),
Chinnarasri et al. ( 2003 ), Dupont et al. ( 2007 ), Wu and Wang ( 2008 ), or Schmocker
and Hager ( 2009 ). This dike erosion process is comparatively simple, as no three-
dimensional (3D) flow patterns occur. Both the temporal water and sediment surfaces
during the erosion process can be recorded across a glass sidewall of the hydraulic
channel. Most past researches simply recorded the breach process using a standard
CCD camera. However, given the spatial breach topography, an observation of the
breach profiles across a channel sidewall is impossible, given the 3D erosion patterns.
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