This small modern river system is located on a retativety flat （about 1°-2°）, unconsotidated sandy pediment surface in the Uinta Basin of Utah, USA, and it is with a scare of about 30 m tong and 0.4-0.8 m ...This small modern river system is located on a retativety flat （about 1°-2°）, unconsotidated sandy pediment surface in the Uinta Basin of Utah, USA, and it is with a scare of about 30 m tong and 0.4-0.8 m wide, simitar as a natural flume experiment modet. The smart stream is informatty divided into upstream, midstream and downstream. The anatysis shows that flood discharge influences channet sinuosity and morphology to produce an initiat meandering pattern which is tater changed to a braided and then a straisht pattern in the downflow direction. The upstream segment has a hish sinuous geometry dominated by both erosion （cutbanks） and deposition （point bars）. In the resistance of sporadic vegetation rooting in banks, the upstream flood deviates its original direction, which resutts in the powerful flood intensively eroding the cutbank and accreting clastics to build point bars, and thus producing a high sinuous channet. The midstream is dominated by deposits （many smart bars） with a moderate to tow sinuosity. Due to the bad drainage of the high sinuous channel in the upstream, the strong flood can cut off the point bar comptetely or even surmount the tevee in the fast meandering upstream, which widens the channel suddenty with a quick decreasing current power. Then, the ctastics from the upstream are untoaded in the midstream and form many smart bars. Untoaded sediments protect the bank, and the tow-power current brings a moderate erosion to the bank, which forms a moderate to tow sinuous channel in the midstream. The downstream shows multistage erosionat terraces in its retativety straight channets. After the midstream water drops its toad, it becomes ＂dear＂ and reaches downstream, the tower current power is hetptess to reform channet 8eometry. Thus, the downstream channel sesment keeps a tower sinuous geometry, evenstraight partially. Small amounts of fine clastics are deposited, and simultaneously multistage terraces are formed due to regressive flood erosion. This stream example demonstrates the subtleties of stream flow and the importance of flood discharge in shaping the channel geometry. Although it is difficult to scale up this example to a large river system that carves geomorphic landscape, this case shows how river geometries vary from the traditional patterns due to different gradient.展开更多
基金supported by National Natural Science Foundation of China(No.41472097 and No.41372125)the Foundation of State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing(No.PRP/open-1608)Guangdong Natural Science Foundation(No.2015A030313193)
文摘This small modern river system is located on a retativety flat （about 1°-2°）, unconsotidated sandy pediment surface in the Uinta Basin of Utah, USA, and it is with a scare of about 30 m tong and 0.4-0.8 m wide, simitar as a natural flume experiment modet. The smart stream is informatty divided into upstream, midstream and downstream. The anatysis shows that flood discharge influences channet sinuosity and morphology to produce an initiat meandering pattern which is tater changed to a braided and then a straisht pattern in the downflow direction. The upstream segment has a hish sinuous geometry dominated by both erosion （cutbanks） and deposition （point bars）. In the resistance of sporadic vegetation rooting in banks, the upstream flood deviates its original direction, which resutts in the powerful flood intensively eroding the cutbank and accreting clastics to build point bars, and thus producing a high sinuous channet. The midstream is dominated by deposits （many smart bars） with a moderate to tow sinuosity. Due to the bad drainage of the high sinuous channel in the upstream, the strong flood can cut off the point bar comptetely or even surmount the tevee in the fast meandering upstream, which widens the channel suddenty with a quick decreasing current power. Then, the ctastics from the upstream are untoaded in the midstream and form many smart bars. Untoaded sediments protect the bank, and the tow-power current brings a moderate erosion to the bank, which forms a moderate to tow sinuous channel in the midstream. The downstream shows multistage erosionat terraces in its retativety straight channets. After the midstream water drops its toad, it becomes ＂dear＂ and reaches downstream, the tower current power is hetptess to reform channet 8eometry. Thus, the downstream channel sesment keeps a tower sinuous geometry, evenstraight partially. Small amounts of fine clastics are deposited, and simultaneously multistage terraces are formed due to regressive flood erosion. This stream example demonstrates the subtleties of stream flow and the importance of flood discharge in shaping the channel geometry. Although it is difficult to scale up this example to a large river system that carves geomorphic landscape, this case shows how river geometries vary from the traditional patterns due to different gradient.
