University of Central Florida Civil and Environmental Engineering CWR4101 Hydrology Lab 8A - Inventory Routing/Pond Design

PURPOSE

The purpose of this lab is to demonstrate the principles of inventory routing and their applicability to the design of stormwater control structures.

EQUIPMENT

• Hydrology and Water Quality Control textbook.
• SMADA Computer Program

PROCEDURE

A watershed is to undergo the following changes in watershed characteristics due to development;

                Before Development      After Development
Total Area          85 acres                85 acres
Impervious Area      0 acres                25 acres
% DCIA               0                      35

Time of Conc.       65 minutes              42 minutes

The pre-development watershed contains a small pond which can store 2 ac-ft feet of water. This pond will be filled in the post condition. The pre-condition watershed is primarily pasture in fair condition, the soils are well drained, and roughly a 50/50 mix over the area of type A and B soils. The pervious areas in the post condition retain these soil characteristics.

You will need to generate hydrographs for this watershed for both the pre and post development conditions. Generate a hydrograph using the SCS Type II distribution for both the 25 and 100 year return periods (24 hour storm). The development is in Orange County, Florida.

Regulations state the peak flow in the post condition must be less than or equal to the pre-condition peak flow. To achieve this a detention pond must be designed. The site which is chosen for this pond is just outside the boundaries of the watershed. The ground is fairly flat at this location at an elevation of 112 feet. The groundwater table is at 108 feet at this location (no temporary storage will be provided by digging the pond deeper than the difference between the ground and groundwater elevations).

Determine a stage-storage-discharge relationship for this pond so that it meets the design requirements. Draw both a plan and x-section view of your pond. Show all elevations on your cross-section. You must select and place an outlet control device (weir) on your pond. Route both the 25 year and 100 year hydrographs through your pond.

A report must be provided which includes the following;

• Watershed characteristics (program input) for both the pre and post conditions with both correctly labeled.
• Peak flow and total volume of flow for watershed hydrographs in both the pre and post condition, both 25 and 100 year storms.
• Plot of pre and post hydrographs for both storms, with peak flow (in cfs) and total volume (in ac-ft) noted on the plot.
• Printout of pond stage-storage-discharge relationship, include information about weir selection and placement.
• X-Section (from side) plot of pond (with weir placement, GW Elevation, ...)
• Plan (from above) plot of pond with contours and elevations labeled. This may be done by hand. The X-Section and Plan drawing should be on the same sheet.
• Routing analysis of Pond for both post-conditions storms, this analysis should have volumes, peak flows, and peak stages. All units and pages should be labeled.
• Plot of pond inflow and outflow for both storms, the plot should have peak flows written on the plot for both the watershed hydrograph and the pond outflow hydrograph.