Observed Erosion Processes During Embankment Overtopping Tests

Abstract

The timing and formation process of a dam embankment breach due to floodovertopping can dramatically impact the rate that water is released from a reservoir. This rate ofwater released directly impacts the hazard to life and property downstream of a breached dam.Therefore, dam embankment erosion and breaching from overtopping events is important to bothengineers and planners alike, who must predict impacts on local communities and surrounding areasaffected by flooding. There is a distinct difference between the erosion processes of a non-cohesiveand cohesive embankment during overtopping. The USDA-ARS has conducted 7 overtopping failuretests on embankments constructed of cohesive materials. The objectives of this paper are to 1)summarize the observed breach erosion processes from the 7 tests into a 4 stage processdescription, 2) provide a detailed description of the erosion processes, breach initiation, breachformation and lateral widening and 3) compare results with dimensionless parameters from historicaldata. The headcut migration rate and widening rates are observed to vary by orders of magnitudedepending on soil materials, yet the migration rate and widening rate are on the same order ofmagnitude for the same soil material.