Mississippi River velocity structure and sediment transport. We are given a set of measurements of the flow velocity within a profile of the Mississippi River, at the time flowing with an approximate flow depth of 8.5 m. The measurements are as follows:

a) Recalling the law of the wall: U=(u_*/k)ln(z/z_o), where k = 0.4, what is your best estimate of the shear velocity, u_*? And what do you find for the roughness length of the flow, z_o? (Recall that von Karman’s constant k = 0.4) Plot your results in both linear-linear and log-linear fashion (linear in U as the x axis and log of z on the y axis), showing both the data and your predicted velocity structure, using your best estimate of u_* and z_o. your predicted velocity structure, using your best estimates for u* and z_o.

b) Given this, what is the slope of the river in this reach? (Note that this is actually a very difficult measurement to make in these cases!) You will have to use the definition of the shear velocity for this calculation: u_* = √gHS.

c) Would coarse quartz silt of diameter 0.125 mm be in suspension here? (The criterion for suspension is that the Rouse number p

Transcribed Image Text:

z (m above bed) 7.7 5.2 3.2 1.8 0.9 0.6 U (m/s) 1.25 1.20 1.05 1.00 0.90 0.80