The dam breach characteristics, specifically the breach geometry and formation time, were estimated by Yochum et al. 2008. The breach width was measured to be 230 ft (70 m), with a top width of 315 ft (96 m), right side slope of 0.61 and a left side slope of 1.3 (horizontal/vertical). In regard to the breach timing, increased discharge from a pre-existing seep was first noticed on Thursday, March 11.Burge, T.R. (2004) Big Bay Dam: Evaluation of Failure Land Partners Limited Partnership, Hattiesburg, MS. The seep gradually increased its discharge, with the flow carrying material by the next morning. At mid-morning on March 12 the seep was inspected and was noticed that it had about a ½ inch of head height. By 12:15 water “shot up out of the hole”. Shortly after this the seep was observed to be “spouting approximately 2 to 3 ft in height, with a diameter of about 18 inches”. The area around the boil then collapsed and the embankment began to rapidly erode. This is the point where the breach is assumed to start, at about 12:20. The final breach dimensions occurred from about 13:10. Full formation is assumed to occur at 13:15—the breach formation time is estimated to be 55 minutes.Report from National Oceanographic and Atmospheric Administration (NOAA) in Jackson, MS
