Breach Morphology Observations of Embankment Overtopping Tests

Dam and embankment breaching from overtopping events is important to both engineers and planners alike, who must predict impacts on local communities and surrounding areas affected by flooding. Models such as DAMBRK, BREACH, and FLDWAV have sought to deal with this problem. Most models, however, have assumed much more simplistic breach morphologies than those observed during actual breach events. Oversimplification resulted partly from a lack of understanding of breach dynamics, and partly from the fact that static erosion processes with symmetric breach geometries were easier to model than continuous erosion dynamics, which form complex geometries. Recent research on overtopping events from both an outdoor flume and full-scale models, with soils ranging from non-plastic SM silty sand to CL lean clay, showed that the erosion process of embankments has a significant impact on timing and rate of breach. This finding shows that the often-used tractive stress procedure may be inconsistent with the process actually occurring.