LAR 512 – Fall 2002

 

PROBLEM #22 – EROSION PROCESSES IN REGIONAL LANDSCAPES


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Go to Snakeden_Branch_Sediment_Data.xl and download the data sets for Snakeden Branch at Reston, Virginia.  This is a data set for USGS Station 1645784 and contains daily stream discharge Q (cfs) and Q (cms), and sediment concentration C (mg/l), sediment load L (tons/day), and load L (Mg/day).

 

The Snakeden Watershed has the following soils, land use, and watershed characteristics:

 

·        Watershed Area = 505.6 acres

·        Soil Mapping Units – Glenelg 55C, Manor 21, and Meadowville 20 (Soil Survey of Fairfax County, Virginia)

·        Zoning – Residential 8, Residential 20, and Planned Residential Community

 

Analyze the data set and prepare calculations to answer the following questions:

 

  1. What is the average daily sediment concentration for the period of record for the Snakeden Branch Watershed?  __________ mg/l

 

  1. What is the average annual sedimentation rate for the period of record for the Snakeden Branch Watershed?  __________ tons/year

 

  1. What is the average yearly sedimentation rate for the period of record for the Snakeden Branch Watershed?  __________ tons/acre/year

 

  1. Use the excel spread sheet and create a scatter plot with X-Axis being Discharge Rate, cfs and Y-Axis being Sediment Concentration, mg/l.  Plot the chart, add linear trendline, and calculate equation and R square for the trendline.

  2. Use the following data for first three watersheds to evaluate a fourth nearby Lake Martin Watershed. All have similar soils, similar density of residential development, similar topography.

 

    1. Snakeden Branch Watershed                505.6 acres      ______ tons/acre/year
    2. Simalix Branch Watershed                    204.8 acres      1.544 tons/acre/year
    3. Stave Run Watershed                             51.2 acres      9.661 tons/acre/year
    4. Lake Martin Watershed                        324.0 acres      ______ tons/acre/year

 

Predict the sedimentation rate for the Lake Martin Watershed in tons/acre/year by creating a scatter plot with X-Axis being Sedimentation Rate, tons/acre/year and Y-Axis being Watershed Size, acres.  Create a linear trendline, equation and R square for the trendline.  What is the predicted Lake Martin Watershed sedimentation rate?  ___________ tons/acre/year