A developer has recently purchased a 10 mi^2 area of land East of Houston near Winnie, Texas.
She is interested in determining the impact that development will have on the hydrological
response of the area. There is one main channel running through the area and the length along it
from outlet to divide is 8 miles. The average slope in this area is 10 feet per mile. To determine
the comparison of hydrographs, a storm with duration 3 hours will be utilized.
Pre-development, the area is 60% wooded (good condition), 20% good condition meadow, and
20% cultivated land with conservation treatment.
Post-development, the watershed will be 20% wooded (good condition), 60% residential with an
average lot size of 1/8 acre, and 20% commercial area. The area has 40% soil type A and 60%
soil type C.
Using the SCS method of unit hydrograph construction and Excel to aid in your calculations and
graphing, plot the resulting triangular hydrographs on the same graph for comparison and note
the differences. How does development affect the hydrograph? What does the resulting
hydrographs tell you about the effects of high or low curve numbers?
Steps in your analysis:
Using the provided SCS spreadsheet determine the hydrograph pre-development
Using the provided SCS spreadsheet determine the hydrograph post-development
Graph Q versus time for both (1) and (2)
Write this up as a technical memo with the following elements
Introduction
Background (Theory)
Method – What tools did you use?
Results – Summary of Appendices
Discussion/Conclusions – Summarize the Project
References – What resources need to be cited?
Appendix A – Pre/Development Run-Off Calculations
Appendix B – Post/Development Run-Off Calculations
Appendix C – Graphs of delta(Q) versus Time and delta(V) versus Time
