1. Nathan Lowe, Shawn Stanley and Jeffery Crump
Runoff Analysis of the Watersheds “El Arroyo El Chilito” and “La Presa Bernardez” Guadalupe, Zacatecas, Mexico
Nathan Lowe, Shawn Stanley and Jeffery Crump

2. The Problem
Between the city of Zacatecas and a nearby town called Guadalupe, a significant amount of urbanization is taking place, which is altering the runoff of two small watersheds, “Arroyo El Chilito” and “la Presa Bernardez”.
Due to the recent development, flooding has increased in frequency and magnitude. The pavement has caused the ground surface to become less permeable, so that precipitation accumulates on the surface rather than absorbing into the soil.
As urbanization continues, this hazard is expected to escalate, a concern to those who are aware of the problem.

3. Data Needed Digital Elevation Model (DEM) Land use distribution
Soil type distribution
Precipitation
Aerial photos and maps

4. Delineation of the Sub-basins
Import the DEM
Run TOPAZ (flow accumulation software)
Choose the outlet point for the basin
Run “Delineate Basins Wizard”

5. DEM Data 30-meter resolution UTM NAD 27 coordinate system
Digital basin delineation by flow accumulation
La Presa Bernardez
El Arroyo El Chilito

6. Land Use and Soil Type Data
Digital images from INEGI (National Institute of Statistics, Geography and Informatics)
Superposition of land use and soil type polygons
Association of permeability with polygons for infiltration calculations
Land Use
Soil Type

7. Precipitation Data
Intensity-Duration-Frequency (IDF) curves from historical data
Design storm:
SCS Type II 2- or 24-hour distribution

8. Projected Flows
By modeling a hypothetical expansion of urbanized areas, the average permeability of the watersheds further decreases.
An additional analysis in HEC-1 and HMS was performed to reflect this change.
Comparing the two scenarios, further development will increase peak flows by approximately 1.5 to 2 times the current flows.

9. HEC-HMS vs HEC-1 Problems with computations
Differences in calculations

10. Hy-8 Culvert Analysis

11. Recommendations La Presa Bernardez El Arroyo El Chilito
Reinstate the existing detention basin by controlling the outflow with an adjustable gate.
Determine the basin volume necessary to effectively delay and attenuate the peak flow through the outlet.
This will reduce the risk of flooding downstream for design storm events.
El Arroyo El Chilito
Clear the debris from the channel downstream of the highway.
Determine if the channel is capable of conveying design storm flows.
Use the abandoned area upstream of the highway as a retention basin.

12. Further Analysis Needed
HEC-RAS models of channels below outlets
Topographical surveys of detention basins above outlets
Basin outlet analyses to size detention basins based on headwater requirements

13. Special thanks to Dr. Jim aka “Mascarita Divina”
Questions?
Special thanks to Dr. Jim aka “Mascarita Divina”