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ES-13

Copyright © 2022 Theodore G. Cleveland

Purpose:

Demonstrate conduit sizing using Rational equation method for eventual application of SWMM for analysis of a storm drainage system.

Objectives:

  • Determine drainage areas to each inlet
  • Determine inlet times and pipe travel times, to size conduits for a storm drain system.
  • Prepare data for hydraulic model testing in SWMM

Problem Statement

Figure 1 is an older (circa 1993) aerial image of a portion of Houston, Texas. The red polygon is the drainage boundary for a storm sewer system that drains North from the part of the area near Westheimer Road to a tributary of Buffalo Bayou and East from the area. The drainage ditch is shown as the “blue” fuzzy line on the figure.

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Figure 1. Tanglewilde Drive Study Area

Drainage in the ditch is from West to East. The two main streets in the study area are highlighted in magenta.

Figure 2 is a map showing storm drainage alignments and inlets location.

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Figure 2. Tanglewilde Drive Storm Drain Inlet and Pipe Alignments.

The figure shows land surface elevations in feet at the indicated locations. A linear scale is shown in the legend. Use the map(s) and:

  1. Construct a land surface elevation contour map using the provided elevation and locations. Get the file from Here
  2. Using your contour map determine the drainage areas to each inlet node. Indicate which nodes you do not assign drainage (junction nodes for connecting pipes).
  3. Use the rational design method to size the conduits for a 5-year storm, for Harris County, Texas.
  4. Specify the invert (flow line) elevations of the nodes (inlets and junction boxes).
  5. Specify the soffit (crown) elevations for the pipes at each node. Submit a memorandum with screen captures of the relevant components above.

Deliverables

A brief report with your solution, showing the requested simulations, tables discharge and depth calculations.

References

  1. Rossman, L. (2009). Storm Water Management Model user’s manual version 5.0. Technical Report
    EPA/600/R-05/040, U.S. Environmental Protection Agency, National Risk Management Research Laboratory Cincinnati, OH 45268

EZ Button Link to ES-5 sample solution

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