EVALUATING EROSION WIDENING AND HEADCUT MIGRATION RATES FOR EMBANKMENT OVERTOPPING TESTS

Abstract

There are a number of recognized technology advancement needs associatedwith watershed structure re-evaluation and rehabilitation. One of those needs, addressed byembankment breach research, is technology for predicting performance during extreme events.Preliminary evaluation of the headcut migration and erosion widening rates during overtoppingand breaching tests on large-scale models are described in this paper. Three large-scaleembankments, 2.3 m and 1.5 m high, have been tested. Two embankments had threehomogeneous test sections and one embankment had one wider test section. Theembankments had 3H:1V slopes on both the upstream and downstream sides. Three soilswere tested, two non-plastic SM silty sand materials and a CL lean clay. The primary erosionprocesses observed were headcut migration and erosion widening. The rates of the erosionprocesses were observed to vary by several orders of magnitude and were observed to bestrongly dependent on the soil material properties. Rates were strongly a function ofcompaction water content. The measured soil properties of erodibility and strength arepromising for the development of physical models to predict embankment overtopping erosionand breach.