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HomeMy WebLinkAbout3338; AGUA HEDIONDA CREEK CHANNEL MAINTENANCE PROJECT; HYDROLOGY AND HYDRAULICS REPORT; 2019-01-21Chang Civil Engineering◦Hydrology◦Hydraulics◦Sedimentation P.O. Box 9496 Rancho Santa Fe, CA 92067-4496 T: 858.692.0760 F: 858.832.1402 wayne@changconsultants.com January 21, 2019 Danny Zimny City of Carlsbad Public Works -Transportation and Engineering 1635 Faraday Avenue Carlsbad, CA 92008 Subject: Agua Hedionda Creek Maintenance Hydraulic Assessment Dear Danny: This letter provides hydraulic analyses to assess benefits resulting from the city of Carlsbad’s Agua Hedionda Creek maintenance activities between Cannon Road and El Camino Real. This creek segment is an engineered trapezoidal channel subject to dense vegetation growth, which significantly reduces its flow capacity. City maintenance has occurred annually in the fall since 2014 and involves removal of select trees and vegetation. The maintenance is performed prior to each rainy season in order to maximize conveyance during subsequent flow periods. The vegetation grows back quickly, so ongoing annual maintenance is needed to maintain capacity. The following three hydraulic modeling scenarios have been assessed for this letter: 1. Existing conditions model prior to maintenance activities, i.e., historic conditions 2. Current conditions without maintenance activities 3. Current conditions with maintenance activities The following describes each scenario. The discussion and results are focused on the study reach between Cannon Road and El Camino Real (Reach) unless otherwise noted. An existing condition HEC-RAS model was prepared by Brown and Caldwell as part of a 2011 Conditional Letter of Map Revision (CLOMR). The CLOMR’s topographic mapping is from 2005 and the vertical datum is NGVD 29. The HEC-RAS cross-section locations are attached. This model was updated downstream of Cannon Road with 2013 field surveyed cross-sections. The updated geometry simulates historic conditions prior to maintenance activities. The historic conditions model was analyzed assuming mature vegetation associated with no maintenance. The associated roughness coefficient is n=0.10. The results are attached and show that the Reach can convey approximately 7,700 cubic feet per second (cfs) before overtopping. The overtopping initiates at cross-section 1488.443. For comparison, the 100-year flow rate is 8,247 cfs. In order to assess current conditions without maintenance, a field survey was performed in October 2018 from Cannon Road to El Camino Real. Cross-sections 1275.89, 1351.03, and 1408.67 were revised based on the field survey to create the current conditions HEC-RAS model. The roughness coefficients are similar to the historic conditions in order to reflect no maintenance. The attached results show that the channel capacity with no maintenance is approximately 5,500 cfs. Overtopping initiates at cross-section 1408.665. This capacity is less than historic conditions by 2,200 cfs. A comparison of the current and historic cross-sections reveals that sediment has naturally deposited by over 2 to over 4 feet in portions of the Reach. The deposition has reduced channel capacity over time. The final HEC-RAS model reflects current conditions immediately after maintenance. The channel roughness coefficient was lowered to n=0.040. The attached results show that the Reach can convey the 100-year flow rate of 8,247 cfs without overtopping. Therefore, maintenance increases the Reach capacity significantly. This provides flood protection for adjacent areas including Cannon Road and El Camino Real. Maintenance also lowers water surface elevations upstream of El Camino Real, which benefits the Rancho Carlsbad Mobile Home Park. In summary, the hydraulic analyses show that the Reach could not convey the 100-year flow rate in the decade prior to maintenance activities. The Reach capacity has lessened over time due to deposition on the channel bed. Ongoing maintenance will increase the capacity significantly and provide flood protection for adjacent roads and residences. Sincerely, Wayne W. Chang, M.S., P.E. Enclosures 14665.7514574.8984527.41533749.9163674.9183574.9233474.9273299.932999.932899.1642499.931488.4431408.6651351.031275.8861238.54824.9947700Aqua Hedionda HEC-RAS Plan: Exist Survey Capacity River: Aqua Hedionda Reach: 1 Profile: BaseFloodReach 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) 1 1870.68 BaseFlood 7700.00 30.85 45.64 38.69 45.94 0.000390 4.85 2731.36 1084.24 0.251 1819.12 BaseFlood 7700.00 30.00 45.63 37.97 45.92 0.000364 4.68 2348.58 1796.46 0.241 1774.959 BaseFlood 7700.00 30.00 45.59 37.16 45.90 0.000336 4.76 2260.12 1814.40 0.231 1724.961 BaseFlood 7700.00 30.00 45.52 37.08 45.88 0.000386 5.03 2699.74 1727.61 0.251 1674.963 BaseFlood 7700.00 31.60 45.49 38.19 45.86 0.000440 5.06 1980.72 1544.01 0.271 1638.348 BaseFlood 7700.00 31.60 45.28 38.44 45.82 0.001111 6.03 1789.09 1588.82 0.301 1599.81 BaseFlood 7700.00 31.60 45.57 38.35 45.66 0.000273 2.55 3182.75 1480.11 0.141 1569.522 Bridge1 1488.443 BaseFlood 7700.00 31.60 44.71 38.35 45.25 0.004528 5.87 1324.76 357.97 0.331 1408.665 BaseFlood 7700.00 31.60 44.30 44.77 0.007509 5.50 1399.73 905.70 0.321 1351.03 BaseFlood 7700.00 31.60 43.86 44.33 0.007843 5.49 1403.19 772.12 0.331 1275.886 BaseFlood 7700.00 31.60 43.04 43.64 0.010186 6.22 1237.44 156.37 0.371 1238.54 BaseFlood 7700.00 31.60 42.78 37.97 43.36 0.005633 6.11 1259.67 146.55 0.371 1200.003 Bridge1 1142.497 BaseFlood 7700.00 32.50 40.15 41.83 0.025732 10.39 741.36 121.31 0.741 1024.058 BaseFlood 7700.00 29.08 38.68 39.08 0.010641 5.20 1516.99 376.20 0.44 05001000150020003040506070Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1870.68Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.0405001000150020002500304050607080Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1819.12Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.04050010001500200025003035404550556065Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1774.959Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.04 0500100015002000303540455055606570Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1724.961Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.040500100015002000304050607080Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1674.963Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.040500100015002000303540455055606570Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1638.348Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.04.075.03.04 0500100015002000304050607080Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1599.81Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.045.0130500100015002000304050607080Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1569.522 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.045.01302004006008001000120030323436384042444648Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1569.522 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.075.1 02004006008001000120030323436384042444648Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1488.443Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.075.1020040060080010001200304050607080Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1408.665Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.1.0302004006008001000120030405060708090Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1351.03Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.1.03 02004006008001000304050607080Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1275.886Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.1.03010020030040050060030323436384042444648Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1238.54Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.075.013010020030040050060030323436384042444648Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1200.003 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.075.013 010020030040050060030323436384042444648Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1200.003 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.045.08.0450100200300400500600323436384042444648Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1142.497Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.075.075.075010020030040050060028303234363840424446Agua Hediona Existing Conditions Plan: AH Exist Cond Survey Capacity RS = 1024.058Station (ft)Elevation (ft)LegendWS BaseFloodGroundBank Sta.075.075.075 HEC-RAS Plan: Current Cond High n Capacity River: Aqua Hedionda Reach: 1 Profile: BaseFloodReach 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(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)1 1870.68 BaseFlood 5500.00 30.85 45.17 37.34 45.35 0.000246 3.75 2324.39 959.371 1819.12 BaseFlood 5500.00 30.00 45.17 36.63 45.33 0.000216 3.52 2072.56 1643.821 1774.959 BaseFlood 5500.00 30.00 45.15 35.79 45.32 0.000196 3.55 1994.64 1701.801 1724.961 BaseFlood 5500.00 30.00 45.07 35.70 45.31 0.000252 3.97 1931.07 1645.421 1674.963 BaseFlood 5500.00 31.60 45.08 36.91 45.28 0.000257 3.77 1727.92 1486.781 1638.348 BaseFlood 5500.00 31.60 44.96 45.26 0.000635 4.48 1375.13 1214.041 1599.81 BaseFlood 5500.00 31.60 45.10 37.06 45.18 0.000272 2.47 2486.47 1472.881 1569.522 Bridge1 1488.443 BaseFlood 5500.00 31.60 44.53 37.06 44.81 0.002464 4.28 1294.00 295.971 1408.665 BaseFlood 5500.00 36.00 43.99 40.48 44.44 0.011080 5.35 1028.07 204.931 1351.03 BaseFlood 5500.00 35.00 43.25 40.10 43.74 0.013156 5.62 978.76174.711 1275.886 BaseFlood 5500.00 34.00 41.22 39.76 42.18 0.034081 7.89 697.19140.801 1238.54 BaseFlood 5500.00 31.60 41.18 36.86 41.62 0.005209 5.33 1031.72 139.521 1200.003 Bridge1 1142.497 BaseFlood 5500.00 32.50 39.42 40.52 0.018849 8.40 655.05 117.081 1024.058 BaseFlood 5500.00 29.08 38.01 38.30 0.009758 4.45 1265.36 371.16 05001000150020003040506070Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1870.68Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.0405001000150020002500304050607080Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1819.12Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.04050010001500200025003035404550556065Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1774.959Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.04 0500100015002000303540455055606570Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1724.961Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.040500100015002000304050607080Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1674.963Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.040500100015002000303540455055606570Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1638.348Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.04.075.03.04 0500100015002000304050607080Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1599.81Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.045.0130500100015002000304050607080Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1569.522 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.045.01302004006008001000120030323436384042444648Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1569.522 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.075.1 02004006008001000120030323436384042444648Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1488.443Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.075.1050100150200250300363840424446Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1408.665Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.1.0305010015020025030035034363840424446Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1351.03Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.1.03 05010015020025030035034363840424446Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1275.886Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.1.03010020030040050060030323436384042444648Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1238.54Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.075.013010020030040050060030323436384042444648Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1200.003 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.075.013 010020030040050060030323436384042444648Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1200.003 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.045.08.0450100200300400500600323436384042444648Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1142.497Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.075.075.075010020030040050060028303234363840424446Agua Hediona Existing Conditions Plan: AH Curr Cond 2018 Survey, Hi n Capacity RS = 1024.058Station (ft)Elevation (ft)LegendWS BaseFloodGroundBank Sta.075.075.075 HEC-RAS Plan: Current Cond Low n River: Aqua Hedionda Reach: 1 Profile: BaseFloodReach 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(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft)1 1870.68 BaseFlood 8092.00 30.85 45.30 38.90 45.68 0.000501 5.39 2432.29 988.991 1819.12 BaseFlood 8092.00 30.00 45.30 38.20 45.65 0.000449 5.10 2148.17 1742.051 1774.959 BaseFlood 8092.00 30.00 45.26 37.39 45.63 0.000411 5.17 2058.68 1776.351 1724.961 BaseFlood 8092.00 30.00 45.08 37.30 45.59 0.000543 5.83 1944.21 1646.141 1674.963 BaseFlood 8092.00 31.60 45.10 38.39 45.54 0.000553 5.54 1739.20 1508.581 1638.348 BaseFlood 8092.00 31.60 44.82 38.67 45.49 0.001437 6.68 1337.48 1146.821 1599.81 BaseFlood 8092.00 31.60 45.14 38.55 45.31 0.000557 3.54 2544.50 1473.471 1569.522 Bridge1 1488.443 BaseFlood 8092.00 31.60 43.98 38.56 44.67 0.001857 6.69 1209.77 136.641 1408.665 BaseFlood 8092.00 36.00 43.05 41.61 44.36 0.006117 9.20 879.56156.321 1351.03 BaseFlood 8092.00 35.00 42.73 41.23 44.00 0.005921 9.02 896.88157.771 1275.886 BaseFlood 8092.00 34.00 41.46 40.93 43.36 0.010174 11.05 732.15 142.281 1238.54 BaseFlood 8092.00 31.60 42.11 38.14 42.86 0.002230 6.96 1162.89 142.901 1200.003 Bridge1 1142.497 BaseFlood 8092.00 32.50 40.26 42.05 0.026994 10.72 754.65 122.001 1024.058 BaseFlood 8092.00 29.08 38.79 39.21 0.010786 5.33 1557.89 377.01 05001000150020003040506070Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1870.68Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.0405001000150020002500304050607080Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1819.12Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.04050010001500200025003035404550556065Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1774.959Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.04 0500100015002000303540455055606570Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1724.961Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.040500100015002000304050607080Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1674.963Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.2.03.040500100015002000303540455055606570Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1638.348Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.04.075.03.04 0500100015002000304050607080Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1599.81Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.045.0130500100015002000304050607080Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1569.522 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.045.01302004006008001000120030323436384042444648Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1569.522 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.04.1 02004006008001000120030323436384042444648Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1488.443Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.04.1050100150200250300363840424446Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1408.665Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.04.0305010015020025030035034363840424446Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1351.03Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.04.03 05010015020025030035034363840424446Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1275.886Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.1.04.03010020030040050060030323436384042444648Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1238.54Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.04.013010020030040050060030323436384042444648Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1200.003 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.013.04.013 010020030040050060030323436384042444648Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1200.003 BRStation (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.045.08.0450100200300400500600323436384042444648Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1142.497Station (ft)Elevation (ft)LegendWS BaseFloodGroundIneffBank Sta.075.075.075010020030040050060028303234363840424446Agua Hediona Existing Conditions Plan: AH Current Cond 2018 Survey Low n RS = 1024.058Station (ft)Elevation (ft)LegendWS BaseFloodGroundBank Sta.075.075.075