一九七六年七月卅一日大汤姆逊河峡谷处下了10英吋(250mm)的暴雨。根据美国地质调查部门间接测量结果,大汤姆逊河在哥罗里达州特拉克附近的峡谷口处的流量为31200cfs(870m~3/s),历史上记载的最大流量为8000cfs(220m~3/s)。河床卵石起初系从小到大排列。作者西门斯沿着洪水在河道流动的观察中,证实了确实存在在洪水之前所没有的逆行沙丘。这可引入结论:被洪水带进河道的沙和沙砾石经过多次洪水后复盖了形成河床的块石,使块石河床如同沙质河床一样。 On July 1, 1976, a 10-inch (250mm) rainstorm occurred at the greater Thomson River Valley. According to the indirect results of the US Geological Survey, the greater Thompson flow at the mouth of the canyon near Trak, Fla., Is 31200 cfs (870 m 3 s -1). The historical maximum flow recorded is 8000 cfs (220 m 3 / s). River bed pebbles initially arranged from small to large. In the observation that Simmons was flowing along the river in a flood, he confirmed the existence of retrograde sand dunes that did not exist before the flood. This leads to the conclusion that sand and gravel, which were brought into the river by floods, covered the bedrock-forming rocks after repeated floods, making the block-stone bed the same as a sandy river bed.