Runoff Analysis of the Watersheds “El Arroyo El Chilito” and “La Presa Bernardez” Guadalupe, Zacatecas, Mexico 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
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.
Data Needed
• Digital Elevation Model (DEM)
• Land use distribution
• Soil type distribution
• Precipitation
• Aerial photos and maps
Delineation of the Sub-basins
1. Import the DEM
2. Run TOPAZ (flow accumulation software)
3. Choose the outlet point for the basin
4. Run “Delineate Basins Wizard”
DEM Data
• 30-meter resolution
• UTM NAD 27 coordinate system
• Digital basin delineation by flow accumulation
La Presa Bernardez
El Arroyo El Chilito
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
Precipitation Data
• Intensity-Duration-Frequency (IDF) curves from historical data
• Design storm:
• SCS Type II 2- or 24-hour distribution
SCS Type II 24-hour Temporal Distribution
0
10
20
30
40
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60
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90
100
0 200 400 600 800 1000 1200 1400
Time (min)
Cu
mu
lati
ve p
erce
nta
ge
of
rain
fall
(%)
Duration Intensity Depth2 hours 21.3 42.624 hours 3.9 93.6
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.
Present Condition Future Condition% Urban Area 2.97% 61.53%Peak Flow (cms) 7.3 13.9Runoff Volume (1000 m^3) 26.7 54.0
5-Year, 2-Hour Storm Runoff for La Presa Bernardez (HMS)
Bernardez RunoffPresent vs. Future
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2
4
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14
16
0 50 100 150 200 250 300
Time (min)
Ou
tflo
w (
cms)
Present Outflow
Future Outflow
HEC-HMS vs HEC-1
• Problems with computations
• Differences in calculations
Future Bernardez Runoff HydrographsHEC-1 vs. HEC-HMS
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2
4
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18
0 50 100 150 200 250 300
Time (min)
Flo
w (
cms)
HEC-1
HMS
Hy-8 Culvert Analysis
Recommendations
• La Presa Bernardez– 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.
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
Questions?
Special thanks to Dr. Jim aka “Mascarita Divina”