FLOOD08628

• County: Costilla
• Community: San Luis
• Stream Name: San Luis area drainageway
• Basin: Rio Grande
• Title: Master Drainage Study Town of San Luis
• Date: 12/1/1988
• Prepared For: San Luis
• Prepared By: WRC Engineering, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

I
I
I
I
.
I
.
.
.
.
I
I
I
I
I
'.
I
I
.

CHAPTER III
HYDROLOGY AND HYDRAULIC ANALYSIS

A. HYDROLOGY ANALYSIS
The hydrologic values and computations for the Rito Seco were obtained from
the USDA SCS close-out report. Discharges for the North Basin (4.5 sq. mi.)
were as follows:

Frequency Flood Di scharge (cfs)
10 year 118
50 yea r 168
100 year 189
500 year 245

For the East Drainage Basin (38.0 sq. mi.) the 100 year flood discharge used
was 680 cfs.

WRC estimated the 100 year flood discharge of Culebra Creek at its confluence
with the Rito Seco from a regional analysis of similar stream basins. The 100
year flood discharge was computed to be 1200 cfs. Background information and
data are presented in the Technical Addendum.

B. HYDRAULIC ANALYSIS
The 100 year water surface profil es and fl oodpl ai n for Cul ebra Creek, Rito
Seco east of the levee, and Rito Seco through the Town were estimated using
the U. S. Army Corps of Engineers HEC-2 Water Surface Profiles computer
program.

For both Culebra Creek and Rito Seco east of the levee, cross sections were
taken by field surveying. Cross section from the SCS closeout report as well
as selected ground shot sections were used for the Rito Seco through Town.

Computer output and a diskette are located in the Technical Addendum.

-11-