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Home My WebLink AboutW.O. 2239-01; Hadley Property-Hadley Trust; Hadley Prpoerty; 1998-09-16HUN SAKE R ^ASSOCIATES SAN DIEGO, INC. PLANNING ENGINEERING SURVEYING IRVINE LAS VEGAS RIVERSIDE SAN DIEGO HYDROLOGY STUDY for HADLEY PROPERTY in the City of Carlsbad Prepared for: Hadley Trust W.O. 2239-01 September 16, 1998 DAVE HAMMAR JACK HILL LEXWILLIMAN 10179 Huennekens St. Suite 200 San Diego, CA 92121 (619) 558-4500 PH (619)558-1414 FX www.hunsaker.com lnfo@HunsakerSD.com Hunsaker & Associates San Diego, Inc. David A. Hammar, R.C.E. President RA:kd k:\2239\1998\a03.doc w.o. 2239-1 TABLE OF CONTENTS References Introduction Executive Summary Vicinity Map Drainage Criteria and Methodology 100-year Post-Development Hydrology Study Reference Data Post-Development Hydrology Map SECTION I I I II III IV V (pocket) RA:msword\\\pcserveiMiydrology*aes92\2239M \hyd.doc W.0.2239-1 09/25/99 References 1) The County of San Diego Drainage Design & Procedure Manual, 1993 2) The County of San Diego Department of Public Works, Public Roads Standards, 1992 3) Master Drainage and Storm Water Quality Management Plan, City of Carlsbad, California, March 1994 4) P&D Technologies, Grading & Erosion Control Plans For Carlsbad Tract 92-3, Drawings Number 341-5A Introduction Hadley Property lies within the City of Carlsbad, California. Development is proposed east of Interstate 5, north of Batiquitos Lagoon, and south of Palomar Airport Road (see fig.1). The subject project consist of 8.8 acres, made up entirely of residential single family homes. Of the 8.8 acres, 7.4 acres are tributary to the existing 30" RCP within Fiona Place (per dwg 341- 5A), which has been constructed to convey a 100-year storm. The existing storm drain was designed to carry 49.6 cfs. Since the proposed runoff from this development is 47.1 cfs, downstream analysis is not required. Since post-development conditions prove to be less than existing conditions, the functionality of the existing storm drain will be adequate. Therefore, the scope of work includes: • Determination of 100-year peak discharge. RA:mswort\tl:\aes92\2239V1\hyd.doc W.0.2239-1 09/23/98 Executive Summary The following table compares existing and post-development flows as determined by the corresponding engineering company's hydrology report: Gbmparty Dwg 341-5A Hunsaker & Associates Existing Flow 49.6 cfs N/A Post-Development Flow N/A 47.1 cfs In summary, the table identifies post-development flows as being less than existing flows. Therefore, since the existing storm drain has been designed and constructed to accomodate a 100-year storm (see dwg 341-5A) and post-development flows are less than existing flows, the existing storm drain does not require upsizing or any other modifications. RA:msword\h:\aes92\2239\1 \tiyd.doc W.0.2239-1 09/28/98 HADLEY PROPERTY OF MARCOS VICINITY MAP N.T.S. FIG.l Ill Drainage Criteria and Methodology Design Storm 100-year storm Land Use Single-family Soil Type A hydrologic soil group "D" was used for this study. Runoff Coefficient "C" values were based on the County of San Diego Drainage Design & Procedure Manual. The site is single- family residential, therefore a "C" value of 0.55 was used. Rainfall Intensity The rainfall intensity values were based on the criteria presented in the County of San Diego Drainage Design & Procedure Manual (see Reference Data). RA:msworflWpcserver*ydrologyiaes92\2239M \ftyd.doc W.O. 2239-1 09/25/98 HYDROLOGY METHOD OF ANALYSIS The computer generated analysis for this watershed is consistent with current engineering standards and requirements of the County of San Diego. This report also contains calculations for the proposed storm drain within the project limits. RATIONAL METHOD The most widely used hydrologic model for estimating watershed peak runoff rates is the rational method. The rational method is applied to small urban and semi-urban areas of less than 0.5 square miles. The rational method equation relates storm rainfall intensity, a selected runoff coefficient, and drainage area to peak runoff rate. This relationship is expressed by the equation: Q = CIA. Where: Q = The peak runoff rate in cubic feet per second at the point of analysis. C = A runoff coefficient representing the area - averaged ratio of runoff to rainfall intensity. I = The time-averaged rainfall intensity in inches per hour corresponding to the time of concentration. A = The drainage basin area in acres. NODE-LINK STUDY In performing a node-link study, the surface area of the basin is divided into basic areas which discharge into different designated drainage basins. These "sub-basins" depend upon locations of inlets and ridge lines. SUBAREA SUMMATION MODEL The rational method modeling approach is widely used due to its simplicity of application, and its capability for estimating peak runoff rates throughout the interior of a study watershed analogous to the subarea model. The procedure for the Subarea Summation Model is as follows: RA: msword\\\pcserver\hydrology\aes92\2239\1 Uiyd .doc W.0.2239-1 09/25/98 (1) Subdivide the watershed into subareas with the initial subarea being less than 10 acres in size (generally 1 lot will do), and the subsequent subareas gradually increasing in size. Assign upstream and downstream nodal point numbers to each subarea in order to correlate calculations to the watershed map. (2) Estimate a Tc by using a nomograph or overlaid flow velocity estimation. (3) Using T, determine the corresponding values of I. Then Q = C I A. (4) Using Q, estimate the travel time between this node and the next by Manning's equation as applied to the particular channel or conduit linking the two nodes. The nodes are joined together by links, which may be street gutter flows, drainage swales or drainage ditches. These links are characterized by length, area, runoff coefficient and cross-section. The Computer subarea menu is as follows: Enter Upstream node number Enter Downstream node number SUBAREA HYDROLOGIC PROCESS 1. Confluence analysis at node. 2. Initial subarea analysis. 3. Pipeflow travel time (computer estimated). 4. Pipeflow travel time (user specified). 5. Trapezoidal channel travel time. 6. Street flow analysis through subarea. 7. User - specified information at node. 8. Addition of sub area runoff to main line. 9. V-gutter flow through area. Select subarea hydrologic process The engineer enters in the pertinent nodes, and then the hydrologic process. Where two or more links join together, the node is analyzed by the confluence method described as follows: RA:mswordWpcserver\hyc!rology\aes92\2239\1 \hyd.doc W.0.2239-1 09/25/98 At the confluence point of two or more basins, the following procedure is used to adjust the total summation of peak flow rates to allow for differences in basin times of concentration. This adjustment is based on the assumption that each basin's hydrographs are triangular in shape. (1). If the collection streams have the same times of concentration, then the Q values are directly summed, Qp = Qa + Qb; Tp = Ta = Tb (2). If the collection streams have different times of concentration, the smaller of the tributary Q values may be adjusted as follows: (i). The most frequent case is where the collection stream with the longer time of concentration has the larger Q. The smaller Q value is adjusted by the ratio of rainfall intensities. QP = Qa + Qb (I A); Tp = Ta (ii). In some cases, the collection stream with the shorter time of concentration has the larger Q. Then the smaller Q is adjusted by a ratio of the T values. Qp = Qb+Qa (VTa); Tp = Tb In a similar way, the underground storm drains are analyzed. The data obtained from the surface model for the flow rates present at the inlets and collection points are input into the nodes representing those structures. The design grades and lengths are used to compute the capacity of the storm drains and to model the travel time into the adjustment of the times of concentration for downstream inlets. REFERENCE 1. Hydrology Manual, County of San Diego, January 1985. 2. Hromadka, Theodore: COMPUTER METHODS IN URBAN HYDROLOGY: Lighthouse Publications, 1983. RA: mswori\\\pcserveiMiydrologyVaes92\2239\1Uiyd.doc W.O. 2239-1 09/25/98 IV **************************************************************************** RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM PACKAGE Reference: SAN DIEGO COUNTY FLOOD CONTROL DISTRICT 1985,1981 HYDROLOGY MANUAL (c) Copyright 1982-93 Advanced Engineering Software (aes) Ver. 1.5A Release Date: 7/10/93 License ID 1239 Analysis prepared by: HUNSAKER & ASSOCIATES Irvine, Inc. Planning * Engineering * Surveying Three Hughes * Irvine , California 92718 * (714) 538-1010 ************************** DESCRIPTION OF STUDY ************************** * HADLEY PROPERTY * * POST-DEVELOPMENT 100-YEAR STORM ANALYSIS * * W.O. #2239-1 SEPTEMBER 24, 1998 * ************************************************************************** FILE NAME: 2239\1\DEV100.RAT TIME/DATE OF STUDY: 15: 7 9/24/1998 USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION: 1985 SAN DIEGO MANUAL CRITERIA USER SPECIFIED STORM EVENT(YEAR) = 100.00 6-HOUR DURATION PRECIPITATION (INCHES) = 2.700 SPECIFIED MINIMUM PIPE SIZE(INCH) = 18.00 SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE = .90 SAN DIEGO HYDROLOGY MANUAL "C"-VALUES USED NOTE: ONLY PEAK CONFLUENCE VALUES CONSIDERED **************************************************************************** FLOW PROCESS FROM NODE 10.00 TO NODE 11.00 IS CODE = 21 >»»RATIONAL METHOD INITIAL SUBAREA ANALYSIS<«« SOIL CLASSIFICATION IS "D" SINGLE FAMILY DEVELOPMENT RUNOFF COEFFICIENT = .5500 INITIAL SUBAREA FLOW-LENGTH = 500.00 UPSTREAM ELEVATION = 366.00 DOWNSTREAM ELEVATION = 350.20 ELEVATION DIFFERENCE = 15.80 URBAN SUBAREA OVERLAND TIME OF FLOW(MINUTES) = 15.086 *CAUTION: SUBAREA SLOPE EXCEEDS COUNTY NOMOGRAPH DEFINITION. EXTRAPOLATION OF NOMOGRAPH USED. 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.489 SUBAREA RUNOFF(CFS) = 4.99 TOTAL AREA(ACRES) = 2.60 TOTAL RUNOFF(CFS) = 4.99 **************************************************************************** FLOW PROCESS FROM NODE 11.00 TO NODE 12.00 IS CODE = 6 >»»COMPUTE STREETFLOW TRAVELTIME THRU SUBAREA<«« UPSTREAM ELEVATION = 350.20 DOWNSTREAM ELEVATION = 339.80 STREET LENGTH(FEET) = 300.00 CURB HEIGHT(INCHES) = 6. STREET HALFWIDTK(FEET) = 28.00 DISTANCE FROM CROWN TO CROSSFALL GRADEBREAK = 14.00 INTERIOR STREET CROSSFALL(DECIMAL) = .020 OUTSIDE STREET CROSSFALL(DECIMAL) = .020 SPECIFIED NUMBER OF HALFSTREETS CARRYING RUNOFF = 2 **TRAVELTIME COMPUTED USING MEAN FLOW(CFS) = 7.00 STREETFLOW MODEL RESULTS: STREET FLOWDEPTH(FEET) = .30 HALFSTREET FLOODWIDTK(FEET) = 8.54 AVERAGE FLOW VELOCITY(FEET/SEC.) = 4.13 PRODUCT OF DEPTH&VELOCITY = 1.23 STREETFLOW TRAVELTIME(MIN) = 1.21 TC(MIN) = 16.30 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.320 SOIL CLASSIFICATION IS "D" SINGLE FAMILY DEVELOPMENT RUNOFF COEFFICIENT = .5500 SUBAREA AREA(ACRES) = 2.20 SUBAREA RUNOFF(CFS) = 4.02 SUMMED AREA(ACRES) = 4.80 TOTAL RUNOFF(CFS) = 9.01 END OF SUBAREA STREETFLOW HYDRAULICS: DEPTH(FEET) = .33 HALFSTREET FLOODWIDTH(FEET) = 10.20 FLOW VELOCITY(FEET/SEC.) = 3.89 DEPTH*VELOCITY = 1.28 c***************************************************************** FLOW PROCESS FROM NODE 12.00 TO NODE 13.00 IS CODE = 6 >»»COMPUTE STREETFLOW TRAVELTIME THRU SUBAREA<«« UPSTREAM ELEVATION = 339.80 DOWNSTREAM ELEVATION = 334.60 STREET LENGTH(FEET) = 368.00 CURB HEIGHT(INCHES) = 6. STREET HALFWIDTH(FEET) = 28.00 DISTANCE FROM CROWN TO CROSSFALL GRADEBREAK = 14.00 INTERIOR STREET CROSSFALL(DECIMAL) = .020 OUTSIDE STREET CROSSFALL(DECIMAL) = .020 SPECIFIED NUMBER OF HALFSTREETS CARRYING RUNOFF = 2 **TRAVELTIME COMPUTED USING MEAN FLOW(CFS) = 11.20 STREETFLOW MODEL RESULTS: STREET FLOWDEPTH(FEET) = .38 HALFSTREET FLOODWIDTH(FEET) = 12.68 AVERAGE FLOW VELOCITY(FEET/SEC.) = 3.25 PRODUCT OF DEPTH&VELOCITY = 1.23 STREETFLOW TRAVELTIME(MIN) = 1.89 TC(MIN) = 18.19 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.093 SOIL CLASSIFICATION IS "D" SINGLE FAMILY DEVELOPMENT RUNOFF COEFFICIENT = .5500 SUBAREA AREA(ACRES) = 2.60 SUBAREA RUNOFF(CFS) = 4.42 SUMMED AREA(ACRES) = 7.40 TOTAL RUNOFF(CFS) = 13.43 END OF SUBAREA STREETFLOW HYDRAULICS: DEPTH(FEET) = .41 HALFSTREET FLOODWIDTH(FEET) = 14.34 FLOW VELOCITY(FEET/SEC.) = 3.09 DEPTH*VELOCITY = 1.28 ************************************************** ****************************** FLOW PROCESS FROM NODE 13.00 TO NODE 14.00 IS CODE = 3 >»»COMPUTE PIPEFLOW TRAVELTIME THRU SUBAREA<«« »»>USING COMPUTER-ESTIMATED PIPESIZE (NON-PRESSURE FLOW)<«« ESTIMATED PIPE DIAMETER(INCH) INCREASED TO 18.000 DEPTH OF FLOW IN 18.0 INCH PIPE IS 6.8 INCHES PIPEFLOW VELOCITY(FEET/SEC.) = 21.9 UPSTREAM NODE ELEVATION = 325.00 DOWNSTREAM NODE ELEVATION = 310.00 FLOWLENGTH(FEET) = 90.00 MANNING'S N = .012 ESTIMATED PIPE DIAMETER(INCH) = 18.00 NUMBER OF PIPES = PIPEFLOW THRU SUBAREA(CFS) = 13.43 TRAVEL TIME(MIN.) = .07 TC(MIN.) = 18.25 *********************************•*•******************************, FLOW PROCESS FROM NODE 14.00 TO NODE 22.00 IS CODE = 51 >»»COMPUTE TRAPEZOIDAL CHANNEL FLOW<«« >»»TRAVELTIME THRU SUBAREA<«« UPSTREAM NODE ELEVATION = 310.00 DOWNSTREAM NODE ELEVATION = 260.00 CHANNEL LENGTH THRU SUBAREA(FEET) = 155.00 CHANNEL SLOPE = .3226 CHANNEL BASE(FEET) = 15.00 "Z" FACTOR = 2.000 MANNING'S FACTOR = .030 MAXIMUM DEPTH(FEET) =20.00 CHANNEL FLOW THRU SUBAREA(CFS) = 13.43 FLOW VELOCITY(FEET/SEC) = 6.94 FLOW DEPTH(FEET) = .13 TRAVEL TIME(MIN.) = .37 TC(MIN.) = 18.63 ****************************************************************************** FLOW PROCESS FROM NODE 14.00 TO NODE 22.00 IS CODE = 1 >»»DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE<«« TOTAL NUMBER OF STREAMS = 2 CONFLUENCE VALUES USED FOR INDEPENDENT STREAM 1 ARE: TIME OF CONCENTRATION(MIN.) = 18.63 RAINFALL INTENSITY(INCH/HR) = 3.05 TOTAL STREAM AREA(ACRES) = 7.40 PEAK FLOW RATE(CFS) AT CONFLUENCE = 13.43 **************************************************************************** FLOW PROCESS FROM NODE 20.00 TO NODE 21.00 IS CODE = 21 >»»RATIONAL METHOD INITIAL SUBAREA ANALYSIS<«« SOIL CLASSIFICATION IS "D" RURAL DEVELOPMENT RUNOFF COEFFICIENT = .4500 NATURAL WATERSHED NOMOGRAPH TIME OF CONCENTRATION WITH 10-MINUTES ADDED = 12.41(MINUTES) INITIAL SUBAREA FLOW-LENGTH = 600.00 UPSTREAM ELEVATION = 384.00 DOWNSTREAM ELEVATION = 310.00 ELEVATION DIFFERENCE = 74.00 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.958 SUBAREA RUNOFF(CFS) = 13.89 TOTAL AREA(ACRES) = 7.80 TOTAL RUNOFF(CFS) = 13.89 **************************************************************************** FLOW PROCESS FROM NODE 21.00 TO NODE 22.00 IS CODE = 51 >»»COMPUTE TRAPEZOIDAL CHANNEL FLOW<«« >»»TRAVELTIME THRU SUBAREA<«« UPSTREAM NODE ELEVATION = 310.00 DOWNSTREAM NODE ELEVATION = 260.00 CHANNEL LENGTH THRU SUBAREA(FEET) = 630.00 CHANNEL SLOPE = .0794 CHANNEL BASE(FEET) = 10.00 "Z" FACTOR = 1.500 MANNING'S FACTOR = .030 MAXIMUM DEPTH(FEET) = 20.00 CHANNEL FLOW THRU SUBAREA(CFS) = 13.89 FLOW VELOCITY(FEET/SEC) = 5.38 FLOW DEPTH(FEET) = .25 TRAVEL TIME(MIN.) = 1.95 TC(MIN.) = 14.36 **************************************************************************** FLOW PROCESS FROM NODE 21.00 TO NODE 22.00 IS CODE = 8 >»»ADDITION OF SUBAREA TO MAINLINE PEAK FLOW<«« 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.602 SOIL CLASSIFICATION IS "D" RURAL DEVELOPMENT RUNOFF COEFFICIENT = .4500 SUBAREA AREA(ACRES) = 7.30 SUBAREA RUNOFF(CFS) = 11.83 TOTAL AREA(ACRES) = 15.10 TOTAL RUNOFF(CFS) = 25.73 TC(MIN) = 14.36 ************************************************************ FLOW PROCESS FROM NODE 21.00 TO NODE 22.00 IS CODE = »>»DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE<«« >»»AND COMPUTE VARIOUS CONFLUENCED STREAM VALUES<«« TOTAL NUMBER OF STREAMS = 2 CONFLUENCE VALUES USED FOR INDEPENDENT STREAM 2 ARE: TIME OF CONCENTRATION(MIN.) = 14.36 RAINFALL INTENSITY{INCH/HR) = 3.60 TOTAL STREAM AREA(ACRES) = 15.10 PEAK FLOW RATE(CFS) AT CONFLUENCE = 25.73 ** CONFLUENCE DATA ** STREAM RUNOFF Tc INTENSITY AREA NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE) 1 13.43 18.63 3.046 7.40 2 25.73 14.36 3.602 15.10 RAINFALL INTENSITY AND TIME OF CONCENTRATION RATIO CONFLUENCE FORMULA US.ED FOR 2 STREAMS. ** PEAK FLOW RATE TABLE ** STREAM RUNOFF Tc INTENSITY NUMBER (CFS) (MIN.) (INCH/HOUR) 1 37.08 14.36 3.602 2 35.18 18.63 3.046 COMPUTED CONFLUENCE ESTIMATES ARE AS FOLLOWS: PEAK FLOW RATE(CFS) = 37.08 Tc(MIN.) = 14.36 TOTAL AREA(ACRES) = 22.50 **************************************************************************** FLOW PROCESS FROM NODE 22.00 TO NODE 23.00 IS CODE = 51 >»»COMPUTE TRAPEZOIDAL CHANNEL FLOW<«« >»»TRAVELTIME THRU SUBAREA<«« UPSTREAM NODE ELEVATION = 260.00 DOWNSTREAM NODE ELEVATION = 244.00 CHANNEL LENGTH THRU SUBAREA(FEET) = 290.00 CHANNEL SLOPE = .0552 CHANNEL BASE(FEET) = 10.00 "Z" FACTOR = 1.500 MANNING'S FACTOR = .030 MAXIMUM DEPTH(FEET) = 10.00 CHANNEL FLOW THRU SUBAREA(CFS) = 37.08 FLOW VELOCITY(FEET/SEC) = 6.89 FLOW DEPTH(FEET) = .50 TRAVEL TIME(MIN.) = .70 TC(MIN.) = 15.06 FLOW PROCESS FROM NODE 22.00 TO NODE 23.00 IS CODE = 8 >»»ADDITION OF SUBAREA TO MAINLINE PEAK FLOW<«« 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.493 SOIL CLASSIFICATION IS "D" RURAL DEVELOPMENT RUNOFF COEFFICIENT = .4500 SUBAREA AREA(ACRES) = 6.40 SUBAREA RUNOFF(CFS) = 10.06 TOTAL AREA(ACRES) = 28.90 TOTAL RUNOFF(CFS) = 47.14 TC(MIN) = 15.06 END OF STUDY SUMMARY: PEAK FLOW RATE(CFS) = 47.14 Tc(MIN.) = 15.06 TOTAL AREA(ACRES) = 28.90 END OF RATIONAL METHOD ANALYSIS V REFERENCE DATA NOTE: Some reference data that has typically been included in support of hydrologic calculations done by hand are incorporated into the Rational Method Hydrology Computer Program Package (by AES). These include: * Intensity-Duration Design Chart * Nomograph for Determination of Time of Concentration (Tc) for Natural Watersheds * Urban Areas Overland Time of Flow Curves * Runoff Coefficients (Rational Method) Since these references are incorporated into the AES software, they are not needed to support this study and are therefore not included in this support. Soils maps are also not included, as Hydrologic Soil Group "D" RA:msword\\\pcserver\ti ydrology\aes92\2239\1Miyd.doc W.0.2239-1 09/25/98 100-YEAR 6-HOUR PRECIPITATION CUfcli'Y OF SAN DIEGO DEPARTMENT OF SANITATION FLOOD CONTROL ISOPLUVIALS PRECIPITATION OF 100-YEAR 6-HOUR OF AN IKCII 33' Pftpn U.S. DEPARTMEN NATIONAL OCfANIC AND AT? SPECIAL STUDIES BRANCH. OFFICE OF II 30' _ m—;^.-:vX:\\f\ ; 27riVr-N\r^-L * •J V>N\\ V iN /|.'rf ^ it by 1 OF COMMERCE SPI1EHIC ADMINISTRATION )ROLOCY. NATIONAL WEATHER SERVICE