Figure 1.   Tecate Creek, in Tecate, Baja California, Mexico (km 8+800).

 

FLOOD HYDROLOGY OF TECATE CREEK,
TECATE, BAJA CALIFORNIA, MEXICO

Victor Miguel Ponce
Professor of Civil and Environmental Engineering
San Diego State University, San Diego, California

 


NARRATIVE SUMMARY

A hydrologic study has been performed with the objective of ascertaining flood peak discharges and related hydrographs for Tecate Creek at Tecate, Baja California, Mexico. The study underpins ongoing studies to restore Tecate Creek to productive stability. The aim is to assure adequate flood conveyance, while preserving and enhancing related hydroecological, socioeconomic, and aesthetic functions.

The hydrologic model RAINFLO, developed at San Diego State University, has been used for these studies. The model subdivides the basin into twentysix (26) subbasins and converts distributed event precipitation into flood runoff following established hydrologic practices. Flood peaks and discharges are calculated for the following return periods: 2, 5, 10, 25, 50 and 100 yr. In addition, the Gumbel method is used to extend the set of modeled peak discharges to the return periods of 200, 500, 1000, 2000, 5000, and 10,000 yr. The 10-yr flood peak, i.e., the regulatory flood, is 268 m3 s-1; the 500-yr flood peak, i.e., the design flood, is 997 m3 s-1; and the 10,000-yr flood peak, i.e., the probable maximum flood, is 1499 m3 s-1.


1.  INTRODUCTION

[Background]    [Methodology]    [Data Collection]    [Results]    [Conclusions]    [References]   •

Tecate Creek, in Tecate, Baja California, Mexico (Figure 1), is being considered by local, state, and federal agencies for rehabilitation. The project encompasses about 11.5 km of Tecate Creek, from the upstream end at Puente San Jose II, east of Tecate proper, to the downstream end at Puente La Puerta, west of Tecate (Figure 2). It is expected that the project will be executed in phases over the next twenty years, as resources become available.


 

Figure 2.   Arrows shows project limits: East at Puente San Jose II, and West at Puente La Puerta.

2.  BACKGROUND

[Methodology]    [Data Collection]    [Results]    [Conclusions]    [References]   •    [Introduction]

The Comisión Nacional del Agua (CNA) [Mexico's National Water Commission], the Secretaría de Infraestructura y Desarrollo Urbano (SIDUE) [Baja California's Department of Intrastructure and Urban Development], and the Ayuntamiento de Tecate [Municipality of Tecate] are three federal, state, and local government agencies, respectively, with jurisdiction over Tecate Creek. Major studies have been performed by Rhoda Arkhos Ingeniería S.C. [the "Rhoda Arkhos" study], the California State Polytechnic University Pomona Studio 606 (the "Pomona" study), and the Centro de Estudios Sociales y Sustentables, in Tijuana (the "CEUSS" study) (Rhoda Arkhos Ingenieria S.C. no date; Centro de Estudios Sociales y Sustentables 2004). Other relevant studies have been completed by Huffman & Carpenter Inc. and San Diego State University's Institute of Regional Studies of the Californias.

 

Figure 3.   Cañada Joe Bill (km 0+200), immediately upstream of its confluence
with Arroyo San Pablo, to form Tecate Creek.

3.  METHODOLOGY

[Data Collection]    [Results]    [Conclusions]    [References]   •    [Introduction]    [Background]

The study will perform event distributed rainfall-runoff modeling on Tecate Creek and its contributing watershed/basin [Campo-Tecate Creek watershed]. The aim is to ascertain flood peaks and related discharge hydrographs for 2-yr to 100-yr return periods. The methodology centers on the choice of model, including its description and data needs.

 

Figure 4.   Upstream view of Tecate Creek at El Descanso (km 1+200), where substantial
channel trasmission losses are likely to take place during floods.


 

Figure 5.   Map of the headwaters of Campo-Tecate Creek, near Live Oak Springs,
San Diego County, California.

4.  DATA COLLECTION

[Results]    [Conclusions]    [References]   •    [Introduction]    [Background]    [Methodology]

The data collection is divided into six phases:

  1. Basin topology

  2. Precipitation

  3. Hydrologic abstractions

  4. Rainfall-runoff transform

  5. Stream channel routing

  6. Channel transmission losses.

The chosen topology for the Campo-Tecate Creek watershed is shown in Figure 6. The U.S.-Mexican border is the straight line that divides the watershed/basin from east to west. The basin is divided into nine (9) upland subbasins (Example:  Miller Creek, upland subbasin 4) and seventeen (17) reach subbasins (Example:  Tecate Creek, reach subbasin 30106). Using computer software tools, the subbasins are delineated following the peaks and saddles in the topography.

 

Figure 6.   Basin topology and subbasin delineation for the Campo-Tecate watershed.

The precipitation value (in or cm) for 2- to 100-yr frequencies was obtained from NOAA Precipitation Atlas 2 (California) (NOAA National Weather Service 1973). The isopluvial curves were extended to cover the portion of the subbasins lying on the Mexican side of the border. An average precipitation value was expressed at the centroid of each subbasin. The results are shown in Figure 7.

 

Figure 7.   Campo-Tecate Creek subbasin precipitation data.

 

Figure 8.   Campo-Tecate Creek subbasin curve numbers (AMC II).

The results of the Campo-Tecate subbasin hydrologic characteristics are shown in Figure 9. The total basin drainage area is 42082.1 ha, or 420.821 km2. The aerial-weighted runoff curve number (AMC II) is CN = 70.

 

Figure 9.   Campo-Tecate Creek subbasin hydrologic characteristics.

The stream-channel routing component of the modeling was performed with the Muskingum-Cunge method (Ponce 1989). The channel reaches (Example: Tecate Creek, reach 30106) were divided into a suitable number of subreaches, depending on the cross-sectional variability. Representative cross sections were measured in the field, and fed to the computer model (Figure 10). With mean channel slope (Figure 9), estimates of Manning's n for center channel, left overbank, and right overbank, and the pertinent cross-sectional data, the model computed the rating curves on which to base the calculation of the routing parameters (Ponce 1989).

The Muskingum-Cunge method requires that the Courant number, defined as the ratio of physical celerity (the "Seddon" celerity) to numerical celerity (the ratio of space step Δx to time step Δt), be kept as close to 1 as practicable. This is for the purpose of assuring good stability and convergence properties (Cunge 1969).

 

Figure 10.   Tecate Creek at Tecate (km 5+000).

5.  RESULTS

[Conclusions]    [References]   •    [Introduction]    [Background]    [Methodology]    [Data Collection]

The Tecate Creek rehabilitation project reach is reach No. 16 in the basin topology, labeled Arroyo Tecate 1, which drains locally reach subbasin 30106 (Figure 6). Accordingly, the results of computer simulations are expressed at two points:

  1. At the upstream point of reach 16 (subbasin 30106), including the contribution of reach 9 (reach subbasin 20503 and its contributing subbasins: 20502, 20501, 10201, 10101, 7, 2, and 1).

  2. At the upstream point of reach 17 (subbasin 30107), including the contribution of reach 10 (reach subbasin 20601 and its contributing subbasin: 8).


Table 1. Simulated peak discharges for Tecate Creek, 2-yr to 100-yr return periods.
Return period
(yr) 		Peak discharge,
upstream of reach 16
(m3 s-1) 		Peak discharge,
upstream of reach 17
(m3 s-1) 		Adopted
peak discharge
(m3 s-1)
2 58 87 87
5 141 190 190
10 206 268 268
25 322 396 396
50 672 675 675
100 770 753 770

 

Figure 11.   10-yr frequency flood hydrograph upstream of reach 16.

 

Figure 12.   10-yr frequency flood hydrograph upstream of reach 17.

 

Figure 13.   100-yr frequency flood hydrograph upstream of reach 16.

 

Figure 14.   10-yr frequency flood hydrograph upstream of reach 17.


The results shown in Table 1 were obtained by distributed conceptual-deterministic event-driven rainfall-runoff modeling. The modeling is distributed because its hydrologic and other relevant data were varied for each one of twenty-six (26) subbasins. The modeling is conceptual because the hydrologic abstraction and rainfall-runoff transform were performed with the NRCS runoff curve number and unit hydrograph methods, respectively.

Q' = 167.574 y - 44.059

Table 2 shows the complete set of peak discharges for Tecate Creek, from 2-yr to 10,000-yr return period.


Table 2. Flood peak discharges for Tecate Creek.
Return period
(yr) 		Flood peak discharge
(m3 s-1)
2 87
5 190
10 268
25 396
50 675
100 770
200 843
500 997
1000 1113
2,000 1230
5,000 1383
10,000 1499

 

6.  CONCLUSIONS

[References]   •    [Introduction]    [Background]    [Methodology]    [Data Collection]    [Results]

A flood hydrology study has been performed for Tecate Creek at Tecate, in northern Baja California, Mexico. The contributing drainage basin straddles the U.S.-Mexican border, with its headwaters in Eastern San Diego County, California (Figure 6). About 60% of the basin lies in the United States.

 

Figure 15.   Tecate Creek near El Descanso, Tecate, showing extent of channel degradation.

 

7.  REFERENCES

•    [Introduction]    [Background]    [Methodology]    [Data Collection]    [Results]    [Conclusions]

California State Polytechnic University Studio 606. 2003. A framework for an urban river environment: Tecate, Mexico.

Centro de Estudios Sociales y Sustentables. 2004. Programa parcial de mejoramiento de la zona Río Tecate. Tijuana, Baja California, Mexico.

Chow, V. T. 1959. Open-channel hydraulics. McGraw-Hill, New York.

 

Fig. 16  Tecate Creek, in Tecate, Baja California, Mexico (km 8+800).

http://ponce.sdsu.edu/tecate_creek_flood_hydrology_report.html 050627