MatLab

College of Engineering and Computing

Department of Civil and Environmental Engineering

CGN 2420 - Computer Tools for Civil Engineers

MATLAB Final Assignment

Selecting the right diameter for storm water drain pipelines Part 1: An intensity-duration-frequency (IDF) curve is a mathematical function that relates the rainfall intensity with its duration and frequency of occurrence. These curves are commonly used in engineering for urban drainage design. The IDF curves for Florida Zone 10 (Miami Dade County) are posted for your usage in Canvas.

Write a script in MATLAB that receives as input parameter a specific storm duration in the range of 0 to 24 hours, and a return period in the range of 2 to 100 years. The code will perform the appropriate calculations and return as an output the rainfall intensity I (in/hr) for Zone 10 in Florida.

Test your program using the following data. Determine the rainfall intensity for each case.

duration (min)

return period (yr)

25 min 5 60 min 20

7 hours 60

Part 2: When selecting the pipe diameter for storm drain pipes two important conditions need to be satisfied, the design velocity must be greater than 3 ft/s to avoid sediment deposits in the pipe, but no more than 15 ft/s to ensure uniform flow. In addition to that, the pipe must be able to move the water only using the gravitational force, for that the Manning equation must be satisfied.

Then, the design procedure is as follows: 1. Select a pipe diameter that satisfies the velocity criteria:

4𝑄

15𝜋 < 𝐷 <

4𝑄

3𝜋

where 𝑄 is the flow rate in cfs (cubic feet per second) and the diameter D is in ft.

2. Select a pipe diameter that also satisfy the Manning equation:

𝐷 > 0.263 𝑄 .

𝑆 .

where 𝑄 is the flow rate in cfs, S is the slope of the pipe (nondimensional) and the diameter D is in ft.

Also, for urban catchments that are not complex and are generally 90 acres or less in size, it is acceptable to use the Rational Method for the calculation of the flow rate. The Rational Method is based on the Rational Formula:

𝑄 = 𝐶𝐼𝐴

where: 𝑄 is the flow rate in cfs, 𝐶 = Runoff coefficient–a non-dimensional coefficient related with the surface of the tributary area. 𝐼 = rainfall intensity (in/hr) for a design return period and storm duration. 𝐴 = tributary area (acres).

Write a script file in MATLAB, that receives as input parameters runoff coefficient, rainfall intensity (in/hr), tributary area (acres), and the drain pipe slope S, and returns as an output only the diameters that satisfy the design criteria from the following list of commercial pipes. Your program should return a vector with the pipe diameters in inches.

Diameter (in) 15 18 21 24 27 30 33 36 42 48 54 60

Test your program with the following input parameters:

Tributary area 𝐴 = 10 acres Runoff coefficient 𝐶 = 0.9 Rainfall intensity 𝐼 = 6.8 in/hr Drainpipe slope 𝑆 = 0.01

Part 3: Create a neat design worksheet in MATLAB, using script from part 1 and script from part 2, to select the diameter for storm water drain pipelines. Determine the less expensive pipe that satisfy each of the following design criteria using your design worksheet:

Storm duration

(min)

Return period (years)

Catchment area

(acres)

Runoff coefficient

Pipe slope

Pipe diameter

(in) Criteria 1 20 10 8.5 0.9 0.005 ? Criteria 2 50 20 8.5 0.85 0.001 ? Criteria 3 150 60 10 0.85 0.010 ?

Project will be discussed in class on Thursday April 15th.