It's not clear to me that velocity necessarily increases as you go from headwaters to mouth. Shouldn't that be discharge, not velocity? On the other hand, this is about the best explanation of Hjulstrom diagram I have seen.
Seems logical that velocity would decrease downstream as slope decreases, right? However likely this seems, the data tells a different story for most rivers. Check out this publication from the USGS: pubs.er.usgs.gov/publication/70184457
Your discussion following that claim of higher velocity downstream is all about discharge, not velocity. You compare Minneapolis, St. Louis, Memphis, and New Orleans. The discussion of sediment grain size at about 2:00, which states big stuff at the headwaters and little stuff at the mouth, implies slower velocity downstream. Again, the discussion of the Hjulstrom diagram is great, better than I have been doing. I know the dynamics are more complicated for a system like the lower Mississippi River, but I want to keep it to the basics for my first-year geology students.
Velocity of the water is determined by a number of factors. Maybe the most obvious is gradient; higher gradient = faster velocity. That would suggest that headwaters should have faster velocity than downstream areas where the gradient is lower. But there are other factors also: 1) roughness of the channel; 2) total water in the channel; 3) shape of the channel, and more. As you move downstream, these factors all change in ways that increase water velocity - channel gets smoother, more water in the channel, for example. The cumulative effects of these all outweigh the gradient as you go downstream, so in the end, average water velocity is faster downstream than it is upstream.
Nice teaching sir and madam. Tomorrow is my test and it made me understand. I have liked too
You guys rock. Thank you so much for making these videos.
It's not clear to me that velocity necessarily increases as you go from headwaters to mouth. Shouldn't that be discharge, not velocity? On the other hand, this is about the best explanation of Hjulstrom diagram I have seen.
Seems logical that velocity would decrease downstream as slope decreases, right? However likely this seems, the data tells a different story for most rivers. Check out this publication from the USGS: pubs.er.usgs.gov/publication/70184457
Your discussion following that claim of higher velocity downstream is all about discharge, not velocity. You compare Minneapolis, St. Louis, Memphis, and New Orleans. The discussion of sediment grain size at about 2:00, which states big stuff at the headwaters and little stuff at the mouth, implies slower velocity downstream. Again, the discussion of the Hjulstrom diagram is great, better than I have been doing. I know the dynamics are more complicated for a system like the lower Mississippi River, but I want to keep it to the basics for my first-year geology students.
Velocity of the water is determined by a number of factors. Maybe the most obvious is gradient; higher gradient = faster velocity. That would suggest that headwaters should have faster velocity than downstream areas where the gradient is lower. But there are other factors also: 1) roughness of the channel; 2) total water in the channel; 3) shape of the channel, and more. As you move downstream, these factors all change in ways that increase water velocity - channel gets smoother, more water in the channel, for example. The cumulative effects of these all outweigh the gradient as you go downstream, so in the end, average water velocity is faster downstream than it is upstream.
Thank you so much
A large % of the erois does occure in the downstrean regions -cutbanks etc
GEOL 101L anyone?