A new mixed used subdivision will be developed in the city of McAllen, TX. Land

Question

A new mixed used subdivision will be developed in the city of McAllen, TX. Land use information and soil characterization is given in Table 1 below. You have been tasked to determine the design parameters (design peak flow and detention volume) for the stormwater detention infrastructure. According to the municipal drainage policy, the detention facility should be able to handle the runoff volume of 50-yr, 1- corresponding to a 10-yr, 1hr storm event under pre-development conditions. The design precipitation depth is distributed according to Table 2. 1. Use the Curve Number method and the NRCS synthetic Unit Hydrograph method to determine the detention volume. Which value of the two methods will govern the design? 2. Since entire land will be developed as described on Table 1 and considering that there is adjacent property available for sale, will the owner be required to purchase additional land for detention purposes? (Assume the city has an ordinance restricting the detention ponds depth to 5 ft). If so, how could you minimize the land needed to be purchased if the owner is old- fashioned and does not want to implement LID techniques? Additional information Determine CN value based on wet conditions (CN-III) Use the Qp values calculated using the CN to calculate the NRCS method hydrograph Use the same Delta t (Table 2) for both methods.

Explanation / Answer

Assuming P= Land use Area % Area CN CN(III) S=(1000/CN)-10 Ia= 0.2S Q= (P-Ia)^2/(P-Ia+S) 215 Residential 1 19% 40.85 75 87.34177215 1.449275362 0.289855 3.601876 Residential 2 17% 36.55 70 84.29319372 1.863354037 0.372671 3.298909 Park 14% 30.1 79 89.63986186 1.155751238 0.23115 3.838559 Commercial 21% 45.15 94 97.29972997 0.277520814 0.055504 4.681724 15% indutrial 19% 40.85 93 96.83114531 0.327255727 0.065451 4.627647 Roads with curbs and drains 10% 21.5 98 99.12049252 0.088731145 0.017746 4.895075 Total 24.94379 Time (min) tp =((tr/2)+tl)and (tl=0.6t) qp=(4.84 *A/t) 0 0 0 6 3.6 0.451649 12 7.2 0.225825 0 18 10.8 0.15055 24 14.4 0.112912 30 18 0.09033 36 21.6 0.075275 42 25.2 0.064521 48 28.8 0.056456 54 32.4 0.050183 60 36 0.045165

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.