Determining character and geometry of the stream channel.

Researchers feel that bankfull ows are the critical ows in determining character and geometry of the stream channel. Others have argued (perhaps less
convincingly) that due to their relatively high magnitude and frequency, bankfull ows may be responsible for accomplishing the largest amount of
geomorphic work (bank erosion, sediment transport, etc.). The size of the bankfull channel of a river is important because it scales the balance of reachscale erosion and deposition with the longer-term ow regime and sediment ux. Rivers will tend to adjust towards an equilibrium condition, wherein the
scale of the channel topography and the size of bed sediments are able to convey recurrent bankfull-level oods.
What data would we need to collect in the eld to determine the bankfull discharge of a river using the Manning equation?
How could we determine the Manning roughness coecient for modern stream ow? What data would we need to collect to do this?
From an environmental standpoint, why are some streams more sensitive to environmental impact than others? If you worked for a consulting rm and were
asked by a client to evaluate the impact of real estate development on a local drainage basin, what would you look for? How would you design your study?
Describe how urbanization (constructing cities with buildings, parking lots, etc.) affects the frequency of large ooding events.
Explain in your own words, how a stream transport and deposits sediments. Make sure that you include all appropriate equations and terms.
State Darcy’s law and explain the core sample method. (Hint: A drawing may be a useful way to present the variables used in Darcy’s law.)
In this exercise you will analyze discharge data from the U.S. Geologic Service (USGS). Data for all USGS gages in the state of New York can be found at:
https://waterwatch.usgs.gov/?m=real&r=ny
Select a gage station by clicking on the circle and then the name of the station (in blue).
From the “Available data for this site” window on the main page for the Missoula gage, go to “Field measurements.” Download “eld measurements” to a tab
separated le, open in Excel. These are data collected over the years at this gaging station by USGS personnel. These data provide a nice record of channel
changes at this site over time. Spend some time looking at the data and understanding what each column represents. All of the analyses below should be
done in metric, so you’ll need to create some new columns with the appropriate unit conversions.
Plot inside gage height versus Q, rst for the data set as a whole, then for the most recent rating set (9). What you’ve plotted here is a stage-discharge rating
curve, which describes the relationship between ow depth (stage) and discharge, for a specic cross-section. The discharges used to develop rating curves
are developed from eld measurements of crosssectional ow area and velocity (Q=UA); then, once a rating curve has been established at a site, discharge
can be determined based on measurements of depth only. So when you see daily/hourly USGS discharge data, these data are based on continuous
automated measurements of depth (stage). Changes in cross-sectional morphology produce changes in stage-discharge relationships, which is why stable
reaches are desirable as gage locations.
Your rating curve probably isn’t a straight line. Would you expect it to be linear or not? Explain your reasoning.
Plot channel width vs time. Is any trend in channel width (i.e., narrowing or widening) evident? Is this plot an accurate way of assessing changes in width?
How would you explain the obvious outliers?
Calculate the width-depth ratio for each measurement. Plot Q vs w:h. What can you infer about cross-section shape and connement from this curve?
Show less