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

Fig. 1.   Tecate Creek, downstream of Tecate, Baja California.

1.  INTRODUCTION [Background]    [Methodology]    [Data Collection]    [Results]    [Conclusions]    [References]    •    [Top]    [Introduction] Tecate Creek, in Tecate, Baja California, Mexico (Fig. 1), is being considered by local, state, and federal agencies for rehabilitation. The project encompasses 11.56 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 (Fig. 2). It is expected that the project will be executed in phases over the next twenty years, as resources become available. The rehabilitation project seeks to provide a host of natural and anthropogenic functions to restore Tecate Creek to productive stability. Several functions will be enhanced by the rehabilitation project. These are: (1) flood conveyance, (2) groundwater replenishment, (3) compliance with federal stream-zoning regulations, (4) preservation of the riparian corridor, (5) enhancement of water quality, and (6) establishment of open areas for parks, sports and recreation, including landscaping and aesthetics. The project is of strategic binational importance, since Tecate Creek forms part of the Tijuana river basin, which straddles the U.S.-Mexican border along the states of California and Baja California. The hydrologic system constituted by Campo-Tecate Creek has its headwaters near Live Oak Springs, in Eastern San Diego County, California, and flows past the town of Campo into Mexico. There it changes name, first to Cañada Joe Bill, and then to Arroyo Tecate (Tecate Creek). Thus, the hydrologic fate of Tecate Creek and its contributing watershed is intertwined with that of Campo Creek, on the U.S. side of the border. A companion study has determined flood discharges for return periods ranging from 2 years to 10,000 years (Ponce et al., 2005). The present study determines the hydraulics of the existing stream channel under a wide range of postulated flood discharges. Thus, this report focuses on the calculation of the water-surface profiles using the Hydrologic Engineering Center's River Analysis System (HEC-RAS) (U.S. Army Corps of Engineers, 2002). The use of this model is necessary to assess the existing stream channel's hydraulic competence to carry the regulatory and design floods. The 11.56-km study reach is currently in various stages of development. This includes: (a) reaches that have been disturbed but are as yet undeveloped, (b) reaches that are currently being planned for development, and (c) reaches where existing planned and/or unplanned development has encroached upon the stream's ability to convey the floods. On the basis of this analysis, several design choices would have to be made by the competent authorities, both federal and local, to guarantee a measure of flood protection to the population of Tecate. Fig. 2.   Tecate Creek project limits: Puente San Jose II (east), and Puente La Puerta (west) (Source: Huffman & Carpenter, Inc.).

2.  BACKGROUND [Methodology]    [Data Collection]    [Results]    [Conclusions]    [References]    •    [Top]    [Introduction]    [Background] The Comisión Nacional del Agua (CNA) [National Water Commission of Mexico], the Secretaría de Infraestructura y Desarrollo Urbano (SIDUE) [Department of Intrastructure and Urban Development of Baja California], and the Ayuntamiento de Tecate [Municipality of Tecate] are the federal, state, and local government agencies, respectively, with jurisdiction over Tecate Creek. Previous studies have been performed by Rhoda Arkhos Ingeniería S.C. (Rhoda Arkhos, undated), the California State Polytechnic University Studio 606 (2003), and the Centro de Estudios Sociales y Sustentables (2004). Other studies have been completed by Huffman & Carpenter, Inc. and the Institute of Regional Studies of the Californias (SDSU). A comprehensive model-based flood hydrology study has been completed for Tecate Creek (Ponce et al., 2005). The specific tool is event rainfall-runoff modeling featuring distributed catchment parameterization. This includes distributed formulations of the following hydrologic processes: (a) precipitation, (b) hydrologic abstraction, (c) rainfall-runoff transform, (d) channel routing, and (e) channel transmission losses. Based on the availability of depth-duration-frequency precipitation data, the catchment modeling (rainfall-runoff) was performed for 2-yr, 5-yr, 10-yr, 25-yr, 50-yr, and 100-yr return periods. Once these values were established, extensions up to the 10,000-yr return period were developed using the Gumbel extreme-value probability distribution (Ponce, 1989). In Mexico and other countries, the 10,000-yr return period is used as a surrogate to the Probable Maximum Precipitation (PMP). Table 1 shows the complete series of flood peak discharges for Tecate Creek. Table 1.   Flood peak discharges for Tecate Creek. Return period (yr) Flood peak discharge (m3s-1) 2 87 5 190 10 268 25 396 50 675 100 770 200 843 500 997 1000 1,113 2,000 1,230 5,000 1,383 10,000 1,499

3.  METHODOLOGY [Data Collection]    [Results]    [Conclusions]    [References]   •    [Top]    [Introduction]    [Background]    [Methodology] The HEC-RAS model calculates water-surface profiles when presented with the appropriate hydraulic and geometric data. The following data is required to run the model: (1) a set of digitized cross sections, (2) the friction coefficients for inbank and overbank flows, (3) the limits of inbank and overbank flows, (4) the lengths of inbank and overbank flows, (5) the design discharge, and (6) a suitable downstream boundary condition. The cross sections are chosen to approximately represent the spatial variability of the stream channel. The limits of inbank and overbank flows are determined based on the field and laboratory examination of the cross-sectional geometry (Fig. 3). The friction coefficients are estimated based on previous experience and established practice (Chow, 1959; Barnes, 1967). The design discharge is that corresponding to the chosen return period (Table 1). The downstream boundary condition is usually taken as a calculated normal stage/depth based on a specified channel slope. Fig. 3.   Upstream view of Tecate Creek at El Descanso.

4.  DATA COLLECTION [Results]    [Conclusions]    [References]   •    [Top]    [Introduction]    [Background]    [Methodology]    [Data Collection] The total length of the modeled reach of Tecate Creek is 11,560 m. To preserve accuracy, the distance between cross sections was chosen as 200 m. Accordingly, a total of 59 cross sections were obtained, based on the available topographic imagery. The topography and channel alignment are shown in Fig. 4. For display purposes, in this figure the total channel length is divided into three reaches: (a) downstream, (b) middle, and (c) upstream.

a. Downstream third

b. Middle third

c. Upstream third

Fig. 4.   Detail of the topography and horizontal alignment.

Table 2 shows the hydraulic and geometric characteristics of Tecate Creek. Column 1 shows sequential numbers for the cross sections. Column 2 shows the cumulative distance, measured from upstream to downstream, as needed for surveying purposes. Column 3 shows the relabeled station distances, from downstream to upstream, as needed for HEC-RAS modeling. Columns 4-6 show left overbank, center channel, and right overbank Manning friction coefficients, respectively. Columns 7 and 8 show left and right overbank station limits, respectively. Columns 9-11 show left overbank, center channel, and right overbank channel lengths, respectively.

Table 2.   Cross-section hydraulic and geometric characteristics for HEC-RAS model.1 No. Distance from u/s (m) HEC-RAS station (m) L. O. n C. Ch. n R. O. n L. O. limit (m) R. O. limit (m) L. O. length (m) Channel length (m) R. O. length (m) (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) 1 0+000 11+560 0.055 0.030 0.055 2.607 28.0871 188.137 200.000 211.863 2 0+200 11+360 0.065 0.035 0.050 53.764 124.326 217.602 200.000 182.398 3 0+400 11+160 0.050 0.030 0.070 19.022 67.456 266.274 200.000 133.726 4 0+600 10+960 0.070 0.035 0.060 166.924 226.002 176.349 200.000 221.998 5 0+800 10+760 0.070 0.035 0.050 87.55 115.806 200.000 200.000 200.000 6 1+000 10+560 0.070 0.035 0.050 5.94 78.873 219.815 200.000 179.794 7 1+200 10+360 0.050 0.030 0.060 43.767 106.121 196.989 200.000 203.009 8 1+400 10+160 0.070 0.040 0.060 44.552 119.128 230.232 200.000 169.768 9 1+600 9+960 0.050 0.035 0.060 50.905 194.257 214.160 200.000 185.840 10 1+800 9+760 0.050 0.035 0.070 7.561 99.223 173.018 200.000 226.982 11 2+000 9+560 0.050 0.030 0.060 12.510 181.616 200.000 200.000 200.000 12 2+200 9+360 0.050 0.030 0.060 110.179 301.564 184.419 200.000 215.581 13 2+400 9+160 0.060 0.035 0.070 253.533 382.722 216.138 200.000 183.862 14 2+600 8+960 0.050 0.035 0.050 157.525 219.931 211.267 200.000 188.733 15 2+800 8+760 0.070 0.035 0.060 198.68 300.81 202.953 200.000 197.047 16 3+000 8+560 0.070 0.050 0.070 45.447 127.35 200.000 200.000 200.000 17 3+200 8+360 0.050 0.030 0.070 30.325 166.778 219.561 200.000 180.066 18 3+400 8+160 0.050 0.030 0.070 9.461 86.307 200.000 200.000 200.000 19 3+600 7+960 0.050 0.030 0.050 79.077 134.986 171.760 200.000 230.516 20 3+800 7+760 0.050 0.035 0.050 95.231 192.080 214.988 200.000 185.012 21 4+000 7+560 0.050 0.030 0.050 71.057 144.537 200.000 200.000 200.000 22 4+200 7+360 0.050 0.030 0.050 109.224 180.096 230.531 200.000 169.470 23 4+400 7+160 0.070 0.035 0.060 162.003 189.080 175.330 200.000 224.670 24 4+600 6+960 0.050 0.030 0.050 361.058 386.521 163.821 200.000 236.180 25 4+800 6+760 0.055 0.035 0.055 116.874 142.036 193.663 200.000 206.337 26 5+000 6+560 0.070 0.040 0.060 193.097 217.756 197.175 200.000 202.825 27 5+200 6+360 0.050 0.045 0.050 300.665 336.592 172.943 200.000 227.057 28 5+400 6+160 0.065 0.050 0.060 259.310 281.740 206.455 200.000 193.545 29 5+600 5+960 0.060 0.045 0.06 214.170 237.200 206.927 200.000 193.073 30 5+800 5+760 0.060 0.040 0.060 162.210 193.060 228.103 200.000 171.897 31 6+000 5+560 0.050 0.030 0.060 79.800 108.100 181.311 200.000 218.689 32 6+200 5+360 0.050 0.035 0.065 321.260 347.500 175.000 200.000 225.000 33 6+400 5+160 0.075 0.050 0.075 319.050 346.000 193.432 200.000 206.568 34 6+600 4+960 0.090 0.070 0.090 334.500 354.400 225.792 200.000 174.208 35 6+800 4+760 0.090 0.070 0.080 214.100 242.400 200.000 200.000 200.000 36 7+000 4+560 0.050 0.050 0.070 110.700 154.200 239.257 200.000 165.657 37 7+200 4+360 0.070 0.050 0.070 40.107 97.658 165.676 200.000 234.335 38 7+400 4+160 0.050 0.035 0.050 91.900 112.141 171.208 200.000 228.792 39 7+600 3+960 0.070 0.055 0.065 141.600 200.500 159.216 200.000 240.784 40 7+800 3+760 0.070 0.040 0.070 162.500 211.600 275.354 200.000 134.774 41 8+000 3+560 0.070 0.050 0.070 146.500 201.300 111.113 200.000 288.887 42 8+200 3+360 0.070 0.035 0.070 161.700 225.000 218.780 200.000 181.703 43 8+400 3+160 0.070 0.035 0.070 30.800 111.300 200.000 200.000 200.000 44 8+600 2+960 0.090 0.070 0.090 93.900 194.600 200.000 200.000 200.000 45 8+800 2+760 0.080 0.040 0.070 73.200 261.600 256.107 200.000 143.893 46 9+000 2+560 0.070 0.040 0.070 56.404 143.345 164.710 200.000 235.290 47 9+200 2+360 0.070 0.035 0.060 220.400 301.800 236.660 200.000 163.340 48 9+400 2+160 0.070 0.040 0.070 39.300 85.600 202.127 200.000 197.872 49 9+600 1+960 0.070 0.035 0.080 50.500 169.500 225.485 200.000 174.515 50 9+800 1+760 0.070 0.040 0.080 85.700 170.100 209.202 200.000 190.614 51 10+000 1+560 0.090 0.050 0.090 161.900 199.629 169.232 200.000 230.768 52 10+200 1+360 0.070 0.035 0.070 133.776 168.146 185.556 200.000 214.444 53 10+400 1+160 0.070 0.035 0.070 93.933 160.866 219.768 200.000 180.232 54 10+600 0+960 0.060 0.035 0.060 4.731 142.056 229.139 200.000 170.861 55 10+800 0+760 0.060 0.035 0.060 79.252 187.027 168.413 200.000 229.121 56 11+000 0+560 0.060 0.035 0.060 96.192 175.461 171.274 200.000 228.726 57 11+200 0+360 0.060 0.035 0.060 26.364 142.680 257.403 200.000 142.597 58 11+400 0+160 0.060 0.035 0.060 28.674 172.544 132.376 160.000 188.749 59 11+560 0+000 0.060 0.035 0.060 58.666 132.860 0.000 0.000 0.000 1 L. O. = left overbank; n = Manning n; C. Ch. = center channel, R. O. = right overbank.

Figure 5 shows the horizontal alignment of the upstream half reach. Figure 6 shows details of the horizontal alignment for this reach. Figure 7 shows the geometric data for the horizontal alignment for this reach.

Fig. 5.   Horizontal alignment of the upstream half reach.

Fig. 6.   Detail of the horizontal alignment of the upstream half reach.

Fig. 7.   Geometric data for the horizontal alignment of the upstream half reach.

Figure 8 shows the horizontal alignment of the downstream half reach. Figure 9 shows details of the horizontal alignment for this reach. Figure 10 shows the geometric data for the horizontal alignment for this reach.

Fig. 8.   Horizontal alignment of the downstream half reach.

Fig. 9.   Detail of the horizontal alignment of the downstream half reach.

Fig. 10.   Geometric data for the horizontal alignment of the downstream half reach.

Three levels of flood discharge are adopted for HEC-RAS modeling. The first level is used in Mexican practice to establish the limits of the regulatory or federal zone (the "Zona Federal"). This level is commonly taken as the 10-yr flood. The second level is used for flood control projects in mid-size cities such as Tecate. This level is established by CNA practice as the 500-yr flood. The third level is the frequency-based flood equivalent to the Probable Maximum Flood. This is the 10,000-yr flood, used to size the freeboard (Natural Resources Conservation Service, 1960; Ponce, 1989). Table 3 shows the design discharges adopted for this study: (1) regulatory, with 10-yr return period; (2) design, with 500-yr return period; and (3) probable maximum, with 10,000-yr return period. Lastly, the downstream boundary condition was specified as a channel slope. This value was determined to be So = 0.00692. Table 3.   Design flood peak discharges for Tecate Creek. Level Level of protection Return period (yr) Flood peak discharge (m3s-1) 1 Regulatory 10 268 2 Design 500 997 3 Maximum 10,000 1,499

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5.  RESULTS [Conclusions]    [References]   •    [Top]    [Introduction]    [Background]    [Methodology]    [Data Collection]    [Results] The results of the HEC-RAS simulation using the existing cross sections are shown in Figs. 11 to 20. Figures 11 to 15 show the results for the 10-yr frequency, and Figs. 16 to 20 show the results for the 500-yr frequency. Figure 11 shows the water-surface profile for the peak discharge corresponding to the 10-yr frequency. Figure 12 shows the 59 calculated cross sections, from 11+560 to 0+000, every 200 m. Figures 13 and 14 show the calculated channel velocities and Froude numbers, respectively. Figure 15 shows the HEC-RAS summary table, including the water-surface elevations for all the cross sections.

Fig. 11.   HEC-RAS water-surface profile, 10-yr frequency (click to enlarge). 11+560 11+360 11+160 10+960 10+760 10+560 10+360 10+160 9+960 9+760 9+560 9+360 9+160 8+960 8+760 8+560 8+360 8+160 7+960 7+760 7+560 7+360 7+160 6+960 6+760 6+560 6+360 6+160 5+960 5+760 5+560 5+360 5+160 4+960 4+760 4+560 4+360 4+160 3+960 3+760 3+560 3+360 3+160 2+960 2+760 2+560 2+360 2+160 1+960 1+760 1+560 1+360 1+160 0+960 0+760 0+560 0+360 0+160 0+000 Fig. 12.   Calculated cross sections for Tecate Creek, 10-yr frequency. Fig. 13.   HEC-RAS channel velocities, 10-yr frequency. Fig. 14.   HEC-RAS Froude numbers, 10-yr frequency. Fig. 15.   HEC-RAS summary table, 10-yr frequency. Figure 16 shows the water-surface profile for the peak discharge corresponding to the 500-yr frequency. Figure 17 shows the 59 calculated cross sections, from 11+560 to 0+000, every 200 m. Figures 18 and 19 show the calculated channel velocities and Froude numbers, respectively. Figure 20 shows the HEC-RAS summary table, including the water-surface elevations for all the cross sections. Fig. 16.   HEC-RAS water-surface profile, 500-yr frequency (click to enlarge).

11+560 11+360 11+160 10+960 10+760 10+560 10+360 10+160 9+960 9+760 9+560 9+360 9+160 8+960 8+760 8+560 8+360 8+160 7+960 7+760 7+560 7+360 7+160 6+960 6+760 6+560 6+360 6+160 5+960 5+760 5+560 5+360 5+160 4+960 4+760 4+560 4+360 4+160 3+960 3+760 3+560 3+360 3+160 2+960 2+760 2+560 2+360 2+160 1+960 1+760 1+560 1+360 1+160 0+960 0+760 0+560 0+360 0+160 0+000 Fig. 17.   Calculated cross sections for Tecate Creek, 500-yr frequency. Fig. 18.   HEC-RAS channel velocities, 500-yr frequency. Fig. 19.   HEC-RAS Froude numbers, 500-yr frequency. Fig. 20.   HEC-RAS summary table, 500-yr frequency.

A second series of HEC-RAS runs was accomplished by designing a prismatic six-point flood channel, to convey the 10-yr flood inbank and the 500-yr flood out-of-bank, including an engineered flood plain. The design cross section was dimensioned to convey the 500-yr flood with a suitable freeboard. Accordingly, the inbank channel was set at 25-m width and 2.5-m depth, with side slopes 2:1 (H:V). The flood plain (out-of-bank channel) was set at 30-m width and 3.5-m depth, with side slopes 2:1 (H:V). Figure 21 shows the water-surface profile for the peak discharge corresponding to the 10-yr, 500-yr, and 10,000-yr frequencies. Figures 22 and 23 shows two typical cross sections: (1) upstream, at 11+560 m, and (2) downstream, at 0+000 m. Figure 24 shows the HEC-RAS summary table, including the water-surface elevations for all seven (7) cross sections. From Fig. 24, it is seen that the freeboard in the inbank channel (10-yr frequency) is: 474.50 - 474.39 = 0.11 m. Likewise, the freeboard for the flood-plain channel for the 500-yr frequency is: 478.00- 476.61 = 1.39 m. Also, the freeboard for the flood-plain channel for the probable maximum flood (10,000-yr) is: 478.00- 477.65 = 0.35 m. Channel velocities are 3.77, 5.74, and 6.50 m/s for the 10-yr, 500-yr, and 10,000-yr floods, respectively. Froude numbers are 0.84, 0.93, and 0.95, respectively. The results are summarized in Table 4. Fig. 21.   HEC-RAS water-surface profile, design cross section (click to enlarge). Fig. 22.   HEC-RAS design cross section at 11+560 (click to enlarge). Fig. 23.   HEC-RAS design cross section at 0+000 (click to enlarge). Fig. 24.   HEC-RAS design cross section summary table.

Table 4.   Hydraulic characteristics of flood-conveyance channel for Tecate Creek. Level Level of protection Return period (yr) Flood peak discharge (m3s-1) Channel depth (m) Channel velocity (m/s) Froude number Freeboard (m) 1 Regulatory 10 268 2.39 3.77 0.84 0.11 1 2 Design 500 997 4.61 5.74 0.93 1.39 2 3 Maximum 10,000 1,499 5.65 6.50 0.95 0.35 2 1 inbank channel.   2 flood-plain channel.

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6.  CONCLUSIONS [References]   •    [Top]    [Introduction]    [Background]    [Methodology]    [Data Collection]    [Results]    [Conclusions] A hydraulic asessment has been made of the ability of the present Tecate Creek to convey regulatory (10-yr) and design (500-yr) flood discharges. It is shown that the current flood channel is limited in some cross sections in its ability to convey the 10-yr and 500-yr floods. An expanded cross section is suggested, together with a vision for a flood-plain channel that can readily double as recreational space. The following conclusions are derived from this study: The 10-yr flood (268 m3/sec) overflows the current low-flow channel in many of the existing cross sections (see cross sections of Fig. 12). The 500-yr flood (997 m3/sec) overflows the current high-flow channel in most of the existing cross sections (see cross sections of Fig. 17). A 25-m width, 2.5-m depth, and size slopes 2H:1V low-flow channel is able to convey the regulatory 10-yr flood. A 30-m width, 3.5-m depth, and size slopes 2H:1V high-flow flood plain is able, when taken together with the low-flow channel, to convey the design 500-yr flood with an adequate freeboard (1.39 m). A 30-m width, 3.5-m depth, and size slopes 2H:1V high-flow flood-plain channel is able to convey the maximum 10,000-yr flood by using most of the available freeboard. Right-of-way and related studies are required to guarantee that the entire reach of Tecate Creek (11.56 km) is in compliance with existing flood control regulations. The proposed 30-m wide flood-plain channel could be used to provide recreational space for the benefit of the local population. A long-term plan for a Tecate river park that reconciles hydrological, ecological, and economic objectives is envisioned.

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REFERENCES •    [Top]    [Introduction]    [Background]    [Methodology]    [Data Collection]    [Results]    [Conclusions]    [References] Barnes, H. A. 1967. Roughness characteristics of natural channels. U.S. Geological Survey Water-Supply Paper 1849, Washington, D.C. http://manningsn.sdsu.edu California State Polytechnic University. 2003. A framework for an urban river environment: Tecate, Mexico. Studio 606, Pomona, California. 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. Natural Resources Conservation Service, 1990. TR-60: Earth dams and reservoirs. Washington, D.C. Ponce, V. M. 1989. Engineering Hydrology, Principles and Practices. Prentice-Hall, Englewood Cliffs, New Jersey. http://ponce.sdsu.edu/330textbook_hydrology_chapters.html Ponce, V. M., H. A. Castro, A. E. Espinoza, R. Celis, and F. Perez. 2005. Flood hydrology of Tecate Creek, Tecate, Baja California, Mexico. http://ponce.sdsu.edu/tecate_creek_flood_hydrology_report.html Rhoda Arkhos Ingeniería S.C., undated. Estudio hidrólogico del Río Tecate. U.S. Army Corps of Engineers. 2002. River Analysis System (HEC-RAS), Hydrologic Engineering Center, Davis, California, Version 3.1, November. http://www.hec.usace.army.mil/software/hec-ras/hecras-hecras.html   Fig. 16  Tecate Creek, in Tecate, Baja California. http://ponce.sdsu.edu/tecate_creek_flood_hydraulics_report.html 060710