Purpose
A new subdivision requires protection from flooding. The hydrologic analysis is complete and now it is time to design diversion channels around the site, analyze the existing channel and then design and analyze culverts at the project entrance. These computations are best completed in a spreadsheet. A sample calculation is attached to the assignment to demonstrate how you may organize your spreadsheet.
Learning Outcomes
At the end of this assignment you will be able to:
- Analyze subcritical, supercritical, critical flow, and uniform flow.
- Design gravity flow pipelines and channels based on design criteria (including hydraulic structure).
- Demonstrate ability to develop hydraulic and hydrologic design report.
Given
- Map Flows
Actions– Contains the Hydrologic Map with the flows. It also contains the elevations to determine the slopes of the proposed system. - Map Design Actions– Shows where you need to design the channels and culverts. It provides data on the existing channel.
- Sample CalculationsActions – A sample calculator is provided as a pdf so that you can set up the project.
- Project TemplateActions – Use the following memorandum template.
Tasks
- In the existing concrete channel find the critical depth, normal depth, channel type and flow velocity then calculate the required Freeboard using the flowrate computed at CP3 shown on Map_Flow.
Freeboard for supercritical flow: 〖〗F_b=1.0+0.025 v〖(y_n)〗^(1/3)
Freeboard for subcritical flow: F_b=0.5+ v^2⁄2g
NOTE: Add the flow depth and the Freeboard depth together to obtain the total channel depth and total channel width.
- Along the north and east boundary lines of the project there is a 20-foot wide utility easement (a strip of land that is dedicated for utilities). You must design channels to divert the flow around the project site by picking the shape, slope, and material for each channel. The design flowrates for the north and east channels are CP1 and CP4 respectively.
- Calculate the critical depth
- Calculate the normal depth
- Calculate the flow velocity
- Determine if the channel is mild or steep.
- Calculate the Freeboard for the north and east channels.
- Size the proposed culverts No. 1 and No. 2 as shown on the proposed conditions drainage map using the flowrates at CP2 and CP3 respectively. Size the culverts such that the pond depth does not exceed 1.5 x the culvert diameter or box height. Provide separate calculation sheets analyzing both culverts.
Submission – Upload to Canvas by Dec 3rd
Develop a design memorandum explain the process you took to complete the tasks. Within the memo should provide text describing what was done and summary tables of your calculations which including columns for Geometry, (bottom width [b], length [l], slope [S], and design flowrate [Q], and velocity [V]). Also include your values for normal depth and velocity in each of the channels. Finally, include three (3) sketches (one for each channel), each showing the channel cross section with the geometry dimensions, normal depth, critical depth and freeboard labeled for the west, north, and east channels.
