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Home My WebLink About6618; AGUA HEDIONDA STREAMBANK RESTORATION; Hydraulic Analysis for Agua Hedionda Streambank; 2015-11-02FOR REVIEW ONLY HYDRAULIC ANALYSIS FOR THE AGUA HEDIONDA STREAMBANK RESTORATION – COMAN November 2, 2015 Chang Civil Engineering ◦ Hydrology ◦ Hydraulics ◦ Sedimentation P.O. Box 9496 Rancho Santa Fe, CA 92067 (858) 692-0760 FOR REVIEW ONLY TABLE OF CONTENTS Introduction ........................................................................................................................................1 Hydraulic Analysis.............................................................................................................................1 Conclusion .........................................................................................................................................2 Restoration Exhibit ............................................................................................................................3 APPENDICES A. HEC-RAS Analysis 1 INTRODUCTION The lower reach of Agua Hedionda Creek is located within the city of Carlsbad. The creek is a natural watercourse where it enters the eastern city limits and remains natural until it reaches the Rancho Carlsbad Mobile Home Park just upstream of Agua Hedionda Lagoon. During flow events, natural watercourses can experience physical changes associated with scour (erosion) or deposition. The southerly bank of Agua Hedionda Creek has recently undergone erosion along the Coman residence at 5855 Sunny Creek Road (see Figure 1), which is approximately 4,500 feet upstream of the Rancho Carlsbad Mobile Home Park. This location is along a bend in the creek, so is subject to additional forces due to the channel curvature. The City is proposing to restore the eroded streambank using a bioengineered solution. This report contains hydraulic analyses of the project area, which are used to assist in the bioengineering design. Figure 1. Erosion Along South Bank of Agua Hedionda Creek HYDRAULIC ANALYSIS An existing condition hydraulic analysis has been performed to determine the flow velocities and shear forces along the project site. The analysis was performed using the US Army Corps of Engineers’ HEC-RAS model. The HEC-RAS input parameters are as follows. HEC-RAS models the physical channel shape with cross-sections spaced along the study reach. The cross-sections are shown on the HEC-RAS Work Map in Appendix A. The cross-sections were created using 1-foot contour interval topographic mapping from the City along the study reach. This mapping was supplemented with 2-foot contour interval mapping from the City’s GIS coverage, where needed. 2 The roughness coefficients of the channel bed and banks were assigned a value of 0.050 to reflect a moderately vegetated channel, which is generally representative of the overall study reach. The 10-, 50-, and 100-year flow rates are included in the model. FEMA only provides the 100- year flow rate near the site, which is 7,810 cubic feet per second. In addition, they provide the 10- and 50-year flow rates at a downstream location in Agua Hedionda Creek, i.e., at the confluence with Buena Creek within the Rancho Carlsbad Mobile Home Park. The 10- and 50- year flow rates at the site were estimated by adjusting the downstream flow rates by the ratio of 100-year flows (see the FEMA peak discharges in Appendix A). The 10-, 50-, and 100-year existing condition HEC-RAS results for the study reach are included in Appendix A. The eroded channel bank is between cross-sections 5 and 7. The results show that the flow velocity between these cross-sections can reach over 7 feet per second, which is considered an erosive flow velocity. The HEC-RAS results along with the channel curvature verify that the natural stream hydraulics have contributed to the bank erosion. CONCLUSION The hydraulic analysis has verified that the eroded slope is naturally subject to velocities (and shear forces) that can cause lateral erosion. The fact that the eroded slope is along a bend in the creek channel indicates that the slope is subject to an increased potential for erosion. The City of Carlsbad proposes to restore the Agua Hedionda Creek streambank using a bioengineered solution developed by Balance Hydrologics, Inc. and Dudek. The solution consists of crib walls along the eroded slope consisting of natural materials such as logs, backfill, boulders, and revegetation (see the exhibit contained after this report text). Balance Hydrologics and Dudek have designed the crib walls to withstand the flow velocities and shear forces determined in this report to a level acceptable to the City. A -- 0+300+200+100+00 90 80 75 85 95 100 105 90 80 75 85 95 100 105 Bank and Channel Stabilization, Agua Hedionda Creek, Coman property, City of Carlsbad, California 215127 Coman Grading.dwg %DODQFH+\GURORJLFV,QF PLAN 1" = 10' SECTION 1" = 5' 10'0'20' SCALE: 1" = 10' 5' REVEGETATION LEGEND CUTTINGS CONTAINER PLANTS & SEEDING NOTE:REFER TO REVEGETATION PLANT LIST, SEED MIX, AND NOTES ON SHEET 2 SHEET 1PRELIMINARY CONCEPT ONLY - NOT FOR CONSTRUCTION THESE PLANS ARE PREPARED TO COMMUNICATE PRELIMINARY CONCEPTS FOR BIOTECHNICAL TREATMENTS FOR EROSION CONTROL. October 7, 2015 APPENDIX A HEC-RAS ANALYSIS 68 TABLE 8: SUMMARY OF PEAK DISCHARGES Peak Discharges (cubic feet per second) Flooding Source and Location Drainage Area (sq. miles) 10% Annual- Chance 2% Annual- Chance 1% Annual- Chance 0.2% Annual- Chance Adobe Creek 2,200 Feet Upstream of Peet Lane 0.67 375 485 560 710 Agua Hedionda Creek At Confluence with Buena Creek 6.3 1,600 4,800 7,000 15,500 2,200 Feet Upstream of Rancho Carlsbad Drive 16.5 --6 -- 7,810 -- Upstream of Calavera Creek 17.3 -- -- 8,080 -- At El Camino Real 23.8 -- -- 9,850 -- Alvarado Creek At Lake Shore Drive 4.6 1,200 2,000 2,300 3,000 At Interstate 8, Near Trailer Park 5.3 1,300 2,200 2,500 3,200 At Interstate 8, Near Murray Boulevard 5.7 1,400 2,400 2,700 3,500 Upstream of Murray Creek 6.3 1,600 2,600 3,000 3,800 Downstream of Murray Creek 10.1 1,700 2,900 3,300 4,200 At Downstream Side of College Avenue 11.4 2,100 3,400 3,900 5,000 Upstream of Tributary Channel 12.1 2,300 3,700 4,300 5,400 Downstream of Tributary Channel 13.4 2,600 4,300 4,800 6,100 -- Data Not Available 1,785 5,355 Interpolated 10- and 50-year flow rates at site in red. FEMA FLOW RATES HEC-RAS Plan: EC FEMA River: RIVER-1 Reach: Reach-1Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Reach-1 1 Approx. 10-Year 1785.00 80.27 87.68 86.4 88.77 0.0114 8.35 214 46.74 0.69Reach-1 1 Approx. 50-Year 5355.00 80.27 90.71 90.6 92.29 0.0114 11.21 620 184.07 0.74Reach-1 1 100-Year 7810.00 80.27 91.85 91.7 93.63 0.0114 12.37 847 215.18 0.76Reach-1 2 Approx. 10-Year 1785.00 78.00 88.08 89.34 0.0095 9.11 207 50.88 0.61Reach-1 2 Approx. 50-Year 5355.00 78.00 91.53 91.5 93.29 0.0118 12.29 594 179.30 0.71Reach-1 2 100-Year 7810.00 78.00 93.13 93.1 94.61 0.0098 12.27 1004 309.37 0.67Reach-1 3 Approx. 10-Year 1785.00 77.60 89.14 84.7 89.67 0.0032 5.99 325 67.81 0.37Reach-1 3 Approx. 50-Year 5355.00 77.60 92.38 90.9 93.76 0.0066 10.37 672 152.24 0.55Reach-1 3 100-Year 7810.00 77.60 93.23 92.9 95.25 0.0093 12.92 808 181.90 0.66Reach-1 4 Approx. 10-Year 1785.00 79.80 89.09 90.05 0.0081 8.32 241 54.82 0.58Reach-1 4 Approx. 50-Year 5355.00 79.80 92.45 92.0 94.36 0.0118 12.60 540 117.14 0.74Reach-1 4 100-Year 7810.00 79.80 93.43 93.4 96.15 0.0153 15.33 665 137.23 0.85Reach-1 5 Approx. 10-Year 1785.00 79.50 89.93 90.33 0.0026 5.25 385 88.01 0.34Reach-1 5 Approx. 50-Year 5355.00 79.50 93.92 94.78 0.0037 8.25 806 136.06 0.43Reach-1 5 100-Year 7810.00 79.50 95.45 96.70 0.0049 10.33 1121 275.49 0.51Reach-1 6 Approx. 10-Year 1785.00 81.00 89.91 90.44 0.0040 6.29 331 85.46 0.43Reach-1 6 Approx. 50-Year 5355.00 81.00 93.95 94.90 0.0046 9.17 775 137.72 0.49Reach-1 6 100-Year 7810.00 81.00 95.51 96.85 0.0058 11.36 1105 284.12 0.57Reach-1 7 Approx. 10-Year 1785.00 81.00 89.72 90.81 0.0095 8.90 240 78.41 0.63Reach-1 7 Approx. 50-Year 5355.00 81.00 93.92 95.15 0.0069 10.69 700 156.48 0.58Reach-1 7 100-Year 7810.00 81.00 95.82 97.04 0.0065 11.56 1174 336.77 0.58Reach-1 8 Approx. 10-Year 1785.00 81.50 90.23 91.24 0.0074 8.85 252 64.58 0.56Reach-1 8 Approx. 50-Year 5355.00 81.50 94.24 95.52 0.0071 11.49 704 157.03 0.59Reach-1 8 100-Year 7810.00 81.50 96.07 97.41 0.0069 12.45 1035 232.63 0.60Reach-1 9 Approx. 10-Year 1785.00 83.77 90.88 91.62 0.0069 7.47 277 74.40 0.56Reach-1 9 Approx. 50-Year 5355.00 83.77 94.64 95.87 0.0066 10.36 678 139.14 0.60Reach-1 9 100-Year 7810.00 83.77 96.07 94.8 97.99 0.0094 13.55 917 256.05 0.73Reach-1 10 Approx. 10-Year 1785.00 83.77 91.33 91.92 0.0046 6.57 327 99.27 0.47Reach-1 10 Approx. 50-Year 5355.00 83.77 95.37 96.17 0.0038 8.35 830 141.99 0.46Reach-1 10 100-Year 7810.00 83.77 97.44 98.38 0.0038 9.42 1205 235.15 0.48 010020030040050080859095100105Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 10Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundBank Sta.05.05.05010020030040050080859095100105Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 9Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundBank Sta.05.05.05 010020030040050080859095100105Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 8Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundBank Sta.05.05.05010020030040050080859095100105Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 7Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundBank Sta.05.05.05 010020030040050080859095100105Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 6Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundBank Sta.05.05.0501002003004005007580859095100Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 5Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundBank Sta.05.05.05 01002003004005007580859095100105Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 4Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundBank Sta.05.05.0501002003004005007580859095100Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 3Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundIneffBank Sta.05.05.05 01002003004007580859095100Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 2Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundBank Sta.05.05.0505010015020025030080859095100Agua Hedionda Creek at Coman Residence Plan: EC FEMA Flows RS = 1Station (ft)Elevation (ft)LegendWS 100-YearWS Approx. 50-YearWS Approx. 10-YearGroundBank Sta.05.05.05