PR-2023-001469 General Plan Amendment, Specific Plan Amendment, Rezone, Site Plan Review, Tentative Tract Map 38624,
Certificate of Appropriateness
Iron Lofts
Appendix F-2
Preliminary Hydrology-Hydraulics Study For Iron Lofts Apartments, 3093 Mission Inn Avenue, Riverside, California
KHR Associates
December 6, 2024
Preliminary Hydrology-Hydraulics Study
For
Iron Lofts Apartments
3093 Mission Inn Avenue
Riverside, California
Prepared for:
Iron Lofts, LLC
1201 Dove Street, Suite 520
Newport Beach, CA 92660
Darrin Olson
(949) 975‐1122
Prepared By:
KHR Associates
17530 Von Karman Avenue, Suite 200
Irvine, CA 92614
James H. Kawamura
(949) 756‐6440
Date: 08/31/2023
Revised Dates: 11/27/2023; 08/09/2024; 12/06/2024
1 PREPARER’S CERTIFICATION
This report has been prepared under the direction of a duly Registered Civil Engineer in the State of California. The civil engineer signing below approves of the technical information included within this report along with recommendations and conclusions made.
_____________________________________
James H. Kawamura, P.E.
Registered Civil Engineer No. C30560
Exp. 3/31/26
Hydrology Report Prepared by
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2 TABLE OF CONTENTS
1.0 Introduction ......................................................................................................................... 3
1.1 Project Description ........................................................................................................... 3
1.2 Project Location ............................................................................................................ 3
1.3 Purpose of the Study ........................................................................................................ 4
2.0 Pre-Development Condition ............................................................................................... 4
2.1 Pre-Development Conditions ........................................................................................... 4
2.1.1 Hydrologic Setting ........................................................................................................ 4
2.1.2 Watershed ................................................................................................................. 5
2.1.3 Existing Topography, Drainage Patterns, and Facilities (Narrative) ........................ 5
2.1.4 Flood Zone ................................................................................................................ 5
2.1.5 Adjacent Land Use .................................................................................................... 5
2.1.6 Soil Conditions.......................................................................................................... 5
2.2 Methodology of Hydrology Study ................................................................................... 5
2.2.1 Design Criteria .............................................................................................................. 6
2.2.2 Rational Method ........................................................................................................... 6
2.3 Hydrology Calculations.................................................................................................... 7
2.3.1 Summary of Drainage Delineation ............................................................................... 7
2.4 Results of Pre-Development Hydrology Calculations ..................................................... 7
3.0 Post Development Condition .............................................................................................. 8
3.1 Post-Development Conditions ...................................................................................... 8
3.2 Methodology of Hydrology Study ................................................................................ 8
3.2.1 Design Criteria .............................................................................................................. 8
3.2.2 Rational Method ........................................................................................................... 8
3.3 Hydrology Calculations.................................................................................................... 8
3.3.1 Summary of Drainage Delineation ............................................................................... 8
3.4 Results of Post-Development Hydrology Calculations .................................................... 9
4.0 Comparison of Post-Development and Pre-Development Hydrologic Conditions ...... 10
4.1 Conclusion ...................................................................................................................... 10
4.2 Proposed Runoff Management Facilities ....................................................................... 10
EXHIBIT
Exhibit A Hydrologic Soils Group Map
Exhibit B Precipitation Maps
APPENDIX
Appendix 1 Pre-Development Hydrology Map
Appendix 1.1 Pre-Development Hydrology Calculations: On-Site plus Off-Site Runoff Appendix 1.2 Pre-Development Hydrology Calculations: 6th Street Off-Site Runoff
Appendix 2 Post-Development Hydrology Map
Appendix 2.1 Post-Development Hydrology Calculations: On-Site plus Off-Site Runoff Appendix 2.1.1 Post-Development Hydrology Calculations: On-Site Appendix 2.2 Post-Development Hydrology Map – Off-Site Appendix 2.3 Post-Development Hydrology Calculations: On-Site plus Off-Site Street Runoff
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3 1.0 Introduction
1.1 Project Description
The proposed Iron Lofts multi-family residential project will consist of 300 residential dwelling units within a 4-story apartment building and 2-story townhome building with a 390-space parking lot on a 6.94 acres site, including a portion of a public street (6 th Street) to be vacated, in the City of Riverside, California. As part of the proposed project, public street improvements, including new curb, gutter, sidewalks, and landscaping will be constructed along Commerce Street, Mission Inn Avenue, and 5th Street frontages.
1.2 Project Location
The project site is bounded by 5 th Street to the north; Commerce Street to the west; Mission Inn Avenue to the south; and a residential neighborhood to the east. The project site currently consists of vacant land, large asphalt covered parking fields, several industrial buildings, and two historic Riverside Recycling buildings.
Figure 1 shows an aerial perspective of the project site and its environs, while Figure 2 illustrates the most current site plan for the proposed project.
Figure 1 – Aerial View of Project Site
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4 Figure 2 – Site Plan
1.3 Purpose of the Study
This drainage study presents an analysis of the hydrologic effects that may be associated with the proposed Iron Lofts multi-family residential project. The study details the general project characteristics, the design, criteria, and methodology applied to the analysis of the area in terms of drainage and associated conveyance facilities.
The plans and specifications in the drainage study are not for construction purposes; the contractor shall refer to final approved construction documents for plans and specifications.
2.0 Pre-Development Condition
2.1 Pre-Development Conditions
2.1.1 Hydrologic Setting
This section summarizes the project’s size and location in the context of the larger watershed perspective, topography, soil and vegetation conditions, percent impervious area, natural and infrastructure drainage features, and other relevant hydrologic and environmental factors to be Hydrology Report Prepared by
Riverside, California KHR Associates
5 protected specific to the project area’s watershed.
2.1.2 Watershed
The proposed project is located within the 2,650 square miles Santa Ana watershed and drains to the Santa Ana River. The watershed includes portions of Lost Angeles, Riverside Counties, and San Bernardino County.
2.1.3 Existing Topography, Drainage Patterns, and Facilities (Narrative)
Adjacent to the subject property, 5th Street slopes from east to west and Commerce Street slopes from north to east.
The existing site currently comprises vacant land, expansive parking areas, several industrial buildings, and two historic Riverside Recycling structures. Stormwater runoff from the property flows out to all adjacent streets, where it eventually gets collected by existing curb and gutter systems. These discharges flowing out to the street occur without stormwater treatment and are collected by existing catch basins connected to the existing storm drain system.
2.1.4 Flood Zone
The subject property is located within Zone X (unshaded), considered to be a minimal risk area outside the 1% and 0.2% annual chance floodplains, as shown on the Federal Emergency Management’s (FEMA) Flood Insurance Rate Map (FIRM) No. 06065C0726G, effective date August 28, 2008.
2.1.5 Adjacent Land Use
The project site is bounded by 5th Street to the north, existing residential uses to the east (within 6th street), Commerce Street to the west and Mission Inn Avenue to the south.
2.1.6 Soil Conditions
According to the geotechnical report prepared by Geotechnical Professionals Inc. (dated May 19, 2021), the site is underlain with predominantly of interbedded layers of sandy silts, silty sands, silts, and sands and is to be medium dense from depths of 20 to 50 feet. The site’s soil is considered hydrologic soil group “C” according to the USDA Natural Resources Conservation Service. (See Exhibit A for Soils Group Map.)
2.2 Methodology of Hydrology Study
This section summarizes the design criteria and methodology applied for the drainage study. The design criteria and methodology follows the Riverside County Flood Control and Water Conservation District (RCFC & WCD) Hydrology Manual (April 1978) noted as “Riverside County Hydrology Manual or RCHM.”
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6 2.2.1 Design Criteria
Local storm drain facilities have been designed to conform to standards found in the RCHM.
Storm drain facilities have been designed to accommodate both the 10-year and 100-year storm events.
2.2.2 Rational Method
Runoff calculations for this study were accomplished using Hydrowin / AES 2016 software, which incorporates the RCFC & WCD Hydrology Manual. This manual uses a method where runoff is assumed to be directly proportional to rainfall and area, less losses for infiltration and depression storage.
Q=CIA
Where... Q = Peak discharge (cfs);
C = runoff coefficient, based on land use and soil type; i = Rainfall intensity (in/hr);
A = watershed area (acre)
The runoff coefficient represents the ratio of rainfall that runs off the watershed versus the portion that infiltrates to the soil or is held in depression storage. The runoff coefficient is dependent on the land use coverage and soil type. The RCFC & WCD Hydrology Manual methodology assumes hydrologic Soil Type C” (Exhibit A) for all soils near the project site.
The watershed time of concentration at any given point is defined as the time it would theoretically take runoff to travel from the most upstream point in the watershed to a concentration point, as estimated by the Time of Concentration Nomograph for Initial Subarea.
Intensity for this site was determined by the intensity-duration curves from the RCHM (See Exhibit B). The runoff coefficient represents the ratio of rainfall that runs off the watershed versus the portion that infiltrates to the soil or is held in depression storage. The runoff coefficient (C) is dependent on rainfall intensity (I), and acreage area (A).
A set of peak discharge rates were computed for both the existing and proposed conditions respectively for the project site to facilitate a comparative analysis between the two scenarios.
Rational Method calculations were accomplished using AES Software. Peak discharges for 10- year, and 100-year hypothetical storm return frequencies were computed and can be seen in the hydrology and drainage analysis section of this report.
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7 2.3 Hydrology Calculations
This section summarizes the quantitative hydrologic analysis of the existing conditions of the site.
2.3.1 Summary of Drainage Delineation
Pre-development Analysis:
To analyze the pre-development conditions, the site was broken into two subareas: A and B (See Exhibit C).
Runoff from subarea A sheet flows southwesterly within an existing curb and gutter on 6th Street. Similarly, runoff from subarea B flows northerly and then westerly, discharging onto Commerce Street. The total runoff from Subareas A and B combine which drains into an existing inlet. The runoff eventually enters an existing storm drain culvert on Commerce Street.
In its current state, the project site also receives 13.21 acres of stormwater runoff from 6th street, designated as Subarea O-1. The flow rate for Subarea O-1 is 14.65cfs for the 10-year storm and
22.71cfs for the 100-year storm. (Refer to Appendix 1, Subarea O-1 for drainage area and spot elevations & Appendix 1.2 for pre-development off-site calculations).
2.4 Results of Pre-Development Hydrology Calculations
Pre-development Calculations:
For the 10-year storm event, the existing site contributes 15.23 cfs of runoff on-site. The existing conditions results for the project site are summarized in Table 1. (See Appendix 1.1 for pre- development calculations).
Table 1: Existing Conditions Hydrology
Storm
Event Subareas Area
(acres)
Q
(cfs)
10-Year A-B 6.94 15.23
O-1 13.21 14.65
Total - 20.15 29.88
100-Year A-B 6.94 22.74
O-1 13.21 22.71
Total - 20.15 45.45
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8 3.0 Post Development Condition
3.1 Post-Development Conditions
The proposed project will have a net increase in total impervious area compared to the existing condition of the site, increasing the site’s overall total imperviousness percentage to 79% and decreases perviousness to 21%.
3.2 Methodology of Hydrology Study
This section summarizes the design criteria and methodology applied for the drainage study. The design criteria and methodology follows the RCFC & WCD Hydrology Manual (April 1978) noted as “Riverside County Hydrology Manual or RCHM.”
3.2.1 Design Criteria
Local storm drain facilities have been designed to conform to standards found in the RCFC & WCD Hydrology Manual (April 1978). Storm drain facilities have been designed to accommodate both the 10-year and 100-year storm events.
3.2.2 Rational Method
Runoff calculations for this study were accomplished using AES 2016 software, which incorporates the RCFC & WCD Hydrology Manual. This manual uses a method where runoff is assumed to be directly proportional to rainfall and area, less losses for infiltration and depression storage. See section 2.2 for more information.
3.3 Hydrology Calculations
This section summarizes the quantitative hydrologic analysis of the proposed conditions of the site.
3.3.1 Summary of Drainage Delineation
Post-development Analysis:
The proposed site is broken into two main drainage areas: A and B (see Appendix 2 ). Each drainage area is further subdivided into multiple smaller subareas.
Stormwater runoff from the buildings in Subareas A and B will be collected by multiple inlets and roof drains, where it will then be collected by the proposed catch basins which will channel the stormwater into the proposed storm drain system. Runoff from the surface areas will flow along the curb and gutter, where it will be collected by multiple catch basins distributed throughout the site. All runoff will be routed for pre-treatment, prior to a solid walled CMP for detention and infiltration by drywells. Stormwater flows exceeding the treatment volume Hydrology Report Prepared by
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9 capacity will bypass the treatment system and continue through the private storm drain system, where it will confluence with the existing stormwater runoff from 6th Street.
A proposed 24” storm drain pipe will be provided to collect and redirect all of the existing runoff on 6th Street. Once the flows combine, the on-site storm drain system will connect to the County’s existing 72” storm drain pipe located on Mission Inn Avenue via a proposed 36” storm drain pipe. Additionally, there is expected to be on-site runoff coming from the proposed planters, specifically subareas B11 and B12. As water flows through these planters, the natural vegetation and soil will help to capture, treat, and manage runoff from the surrounding areas.
This treated runoff will then be directed towards its respective street via the proposed catch basin. (Refer to Appendix 2.2 for map and Appendix 2.3 for calculations). For catch basins and storm pipes in the public right of way, sizing will be provided during the final design phase.
The project site in its post-development condition will intercept stormwater from 6 th street and adjacent properties towards the east (Refer to Subarea O-1 from Appendix 2; and Section 3.4 for flow rates). This stormwater will not negatively impact the new development as it will be directed in a City-owned catch basin and storm drain pipe (with a maintenance easement), discharging south towards Mission Avenue through a new RCP pipe, which will connect to the existing 72-inch storm pipe (See Appendix 2.1 for the addition of subarea O-1 to the development).
3.4 Results of Post-Development Hydrology Calculations
Post-development Calculations:
Under post-development conditions, the site will produce 23.64 cfs of stormwater runoff, which will be collected by the private storm drain system and will be routed to the proposed tanks for detention prior to infiltration by means of drywells. The proposed conditions results for the project site are summarized in Table 2. (See Appendices 2.1 and 2.3 for post-development calculations).
Table 2: Proposed Conditions Hydrology
Storm
Event Subareas Area
(acres)
Q
(cfs)
10-Year A1-A12, B1-B10, O-1 19.6 23.64
B11, B12 0.6 1.16
Total - 20.2 24.08
100-Year A1-A11, B1-B10, O-1 19.6 36.04
B11, B12 0.6 1.75
Total - 20.2 37.79
Hydrology Report Prepared by
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10 4.0 Comparison of Post-Development and Pre-Development Hydrologic Conditions
4.1 Conclusion
Site Analysis Results:
Table 3: Hydrology Comparative Analysis
Storm Event Pre-development Condition
(Q)
Post-development Condition
(Q)
10-Year 29.88 cfs 23.64 cfs
100-Year 45.45 cfs 36.04 cfs
The results from the AES calculations show that the post-development condition will generate a lower peak flow rate compared to the pre-development condition (See Table 1 above). This reduction in runoff is attributed to the extended drainage flow path and the utilization of underground storm drain piping. Furthermore, the existing site land-use is industrial/commercial; whereas, the proposed development is for multi-family residential use.
The post-development condition results do not account the additional reduction in runoff volume due to the infiltration of the required stormwater quality design volume. Therefore, the proposed development will not negatively impact the downstream storm drain system or receiving waters.
4.2 Proposed Runoff Management Facilities
The proposed facilities managing runoff from the area include:
Water quality treatment control Best Management Practices (BMPs); specifically, Aqua Swirl Hydrodynamic Separator Treatment device and Drywell Systems.
Proposed perforated corrugated steel infiltration tanks will be placed on the project site.
Hydrology Report Prepared by
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EXHIBITS
EXHIBIT A
Hydrologic Soils Group Map
Project Location
Hydrology Report Prepared by
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EXHIBIT B
Precipitation Maps
Hydrology Report Prepared by
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APPENDICES
Hydrology Report Prepared by
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Appendix 1
Pre-Development Hydrology Map
Hydrology Report Prepared by
Riverside, California KHR Associates
Appendix 1.1
Pre-Development Hydrology Calculations:
On-Site plus Off-Site Runoff
____________________________________________________________________________ ****************************************************************************
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT (RCFC&WCD) 1978 HYDROLOGY MANUAL
(c) Copyright 1982-2016 Advanced Engineering Software (aes) (Rational Tabling Version 23.0)
Release Date: 07/01/2016 License ID 1681
Analysis prepared by:
KHR Associates
17530 Von Karman Avenue
Irvine, CA 92626
************************** DESCRIPTION OF STUDY ************************** * IRON LOFTS * * PRE-DEVELOPMENT HYDROLOGY - INCLUDING OFF-SITE AREA * * 10-YEAR STORM EVENT * ************************************************************************** FILE NAME: RIL1-E10.DAT
TIME/DATE OF STUDY: 09:30 08/05/2024
---------------------------------------------------------------------------- USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
---------------------------------------------------------------------------- USER SPECIFIED STORM EVENT(YEAR) = 10.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 4.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE = 0.95 10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 2.140
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = 0.800
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 3.210
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = 1.200
SLOPE OF 10-YEAR INTENSITY-DURATION CURVE = 0.5491525
SLOPE OF 100-YEAR INTENSITY-DURATION CURVE = 0.5491524 COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 10.00 1-HOUR INTENSITY(INCH/HOUR) = 0.808 SLOPE OF INTENSITY DURATION CURVE = 0.5492
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED FOR RATIONAL METHOD NOTE: CONSIDER ALL CONFLUENCE STREAM COMBINATIONS
FOR ALL DOWNSTREAM ANALYSES
*USER-DEFINED STREET-SECTIONS FOR COUPLED PIPEFLOW AND STREETFLOW MODEL* HALF- CROWN TO STREET-CROSSFALL: CURB GUTTER-GEOMETRIES: MANNING
WIDTH CROSSFALL IN- / OUT-/PARK- HEIGHT WIDTH LIP HIKE FACTOR NO. (FT) (FT) SIDE / SIDE/ WAY (FT) (FT) (FT) (FT) (n) === ===== ========= ================= ====== ===== ====== ===== ======= 1 30.0 20.0 0.018/0.018/0.020 0.67 2.00 0.0313 0.167 0.0150 GLOBAL STREET FLOW-DEPTH CONSTRAINTS:
1. Relative Flow-Depth = 0.00 FEET
as (Maximum Allowable Street Flow Depth) - (Top-of-Curb)
2. (Depth)*(Velocity) Constraint = 6.0 (FT*FT/S)
*SIZE PIPE WITH A FLOW CAPACITY GREATER THAN
OR EQUAL TO THE UPSTREAM TRIBUTARY PIPE.*
**************************************************************************** FLOW PROCESS FROM NODE 1.00 TO NODE 2.00 IS CODE = 21 ---------------------------------------------------------------------------- >>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS COMMERCIAL
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW-LENGTH(FEET) = 292.06
UPSTREAM ELEVATION(FEET) = 882.24
DOWNSTREAM ELEVATION(FEET) = 878.78
ELEVATION DIFFERENCE(FEET) = 3.46
TC = 0.303*[( 292.06**3)/( 3.46)]**.2 = 7.129
10 YEAR RAINFALL INTENSITY(INCH/HOUR) = 2.603
COMMERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .8832
SOIL CLASSIFICATION IS "C"
SUBAREA RUNOFF(CFS) = 8.00
TOTAL AREA(ACRES) = 3.48 TOTAL RUNOFF(CFS) = 8.00 **************************************************************************** FLOW PROCESS FROM NODE 2.00 TO NODE 2.00 IS CODE = 10 ---------------------------------------------------------------------------- >>>>>MAIN-STREAM MEMORY COPIED ONTO MEMORY BANK # 1 <<<<< ============================================================================ **************************************************************************** FLOW PROCESS FROM NODE 2.00 TO NODE 2.00 IS CODE = 13 ---------------------------------------------------------------------------- >>>>>CLEAR THE MAIN-STREAM MEMORY<<<<<
============================================================================ **************************************************************************** FLOW PROCESS FROM NODE 27.20 TO NODE 27.30 IS CODE = 21 ---------------------------------------------------------------------------- >>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS SINGLE FAMILY (1/4 ACRE)
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW-LENGTH(FEET) = 2313.53
UPSTREAM ELEVATION(FEET) = 910.75
DOWNSTREAM ELEVATION(FEET) = 881.40
ELEVATION DIFFERENCE(FEET) = 29.35
TC = 0.393*[( 2313.53**3)/( 29.35)]**.2 = 20.845
10 YEAR RAINFALL INTENSITY(INCH/HOUR) = 1.444
SINGLE-FAMILY(1/4 ACRE LOT) RUNOFF COEFFICIENT = .7681
SOIL CLASSIFICATION IS "C"
SUBAREA RUNOFF(CFS) = 14.65
TOTAL AREA(ACRES) = 13.21 TOTAL RUNOFF(CFS) = 14.65 +--------------------------------------------------------------------------+ | SUBAREA O-1 | | | | | +--------------------------------------------------------------------------+ **************************************************************************** FLOW PROCESS FROM NODE 27.30 TO NODE 27.30 IS CODE = 10 ---------------------------------------------------------------------------- >>>>>MAIN-STREAM MEMORY COPIED ONTO MEMORY BANK # 2 <<<<< ============================================================================ **************************************************************************** FLOW PROCESS FROM NODE 27.30 TO NODE 27.30 IS CODE = 13 ---------------------------------------------------------------------------- >>>>>CLEAR THE MAIN-STREAM MEMORY<<<<<
============================================================================ **************************************************************************** FLOW PROCESS FROM NODE 3.00 TO NODE 4.00 IS CODE = 21 ---------------------------------------------------------------------------- >>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS COMMERCIAL
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW-LENGTH(FEET) = 413.62
UPSTREAM ELEVATION(FEET) = 882.78
DOWNSTREAM ELEVATION(FEET) = 876.31
ELEVATION DIFFERENCE(FEET) = 6.47
TC = 0.303*[( 413.62**3)/( 6.47)]**.2 = 7.751
10 YEAR RAINFALL INTENSITY(INCH/HOUR) = 2.486
COMMERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .8825
SOIL CLASSIFICATION IS "C"
SUBAREA RUNOFF(CFS) = 7.59
TOTAL AREA(ACRES) = 3.46 TOTAL RUNOFF(CFS) = 7.59 **************************************************************************** FLOW PROCESS FROM NODE 4.00 TO NODE 4.00 IS CODE = 11 ---------------------------------------------------------------------------- >>>>>CONFLUENCE MEMORY BANK # 1 WITH THE MAIN-STREAM MEMORY<<<<< ============================================================================ ** MAIN STREAM CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 7.59 7.75 2.486 3.46
LONGEST FLOWPATH FROM NODE 3.00 TO NODE 4.00 = 413.62 FEET. ** MEMORY BANK # 1 CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 8.00 7.13 2.603 3.48
LONGEST FLOWPATH FROM NODE 1.00 TO NODE 4.00 = 292.06 FEET. ** PEAK FLOW RATE TABLE **
STREAM RUNOFF Tc INTENSITY
NUMBER (CFS) (MIN.) (INCH/HOUR)
1 14.98 7.13 2.603
2 15.23 7.75 2.486
COMPUTED CONFLUENCE ESTIMATES ARE AS FOLLOWS:
PEAK FLOW RATE(CFS) = 15.23 Tc(MIN.) = 7.75
TOTAL AREA(ACRES) = 6.9
**************************************************************************** FLOW PROCESS FROM NODE 4.00 TO NODE 4.00 IS CODE = 11 ---------------------------------------------------------------------------- >>>>>CONFLUENCE MEMORY BANK # 2 WITH THE MAIN-STREAM MEMORY<<<<< ============================================================================ ** MAIN STREAM CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 14.98 7.13 2.603 6.94
2 15.23 7.75 2.486 6.94
LONGEST FLOWPATH FROM NODE 3.00 TO NODE 4.00 = 413.62 FEET. ** MEMORY BANK # 2 CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 14.65 20.84 1.444 13.21
LONGEST FLOWPATH FROM NODE 27.20 TO NODE 4.00 = 2313.53 FEET. ** PEAK FLOW RATE TABLE **
STREAM RUNOFF Tc INTENSITY
NUMBER (CFS) (MIN.) (INCH/HOUR)
1 19.99 7.13 2.603
2 20.68 7.75 2.486
3 23.50 20.84 1.444
COMPUTED CONFLUENCE ESTIMATES ARE AS FOLLOWS:
PEAK FLOW RATE(CFS) = 23.50 Tc(MIN.) = 20.84
TOTAL AREA(ACRES) = 20.1
============================================================================ END OF STUDY SUMMARY:
TOTAL AREA(ACRES) = 20.1 TC(MIN.) = 20.84 PEAK FLOW RATE(CFS) = 23.50
*** PEAK FLOW RATE TABLE ***
Q(CFS) Tc(MIN.)
1 19.99 7.13
2 20.68 7.75
3 23.50 20.84
============================================================================ ============================================================================
END OF RATIONAL METHOD ANALYSIS
____________________________________________________________________________ ****************************************************************************
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT (RCFC&WCD) 1978 HYDROLOGY MANUAL
(c) Copyright 1982-2016 Advanced Engineering Software (aes) (Rational Tabling Version 23.0)
Release Date: 07/01/2016 License ID 1681
Analysis prepared by:
KHR Associates
17530 Von Karman Avenue
Irvine, CA 92626
************************** DESCRIPTION OF STUDY ************************** * IRON LOFTS * * PRE-DEVELOPMENT HYDROLOGY - INCLUDING OFF-SITE AREA * * 100-YEAR STORM EVENT * ************************************************************************** FILE NAME: RIL1-E10.DAT
TIME/DATE OF STUDY: 09:30 08/05/2024
---------------------------------------------------------------------------- USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
---------------------------------------------------------------------------- USER SPECIFIED STORM EVENT(YEAR) = 100.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 4.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE = 0.95 10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 2.140
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = 0.800
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 3.210
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = 1.200
SLOPE OF 10-YEAR INTENSITY-DURATION CURVE = 0.5491525
SLOPE OF 100-YEAR INTENSITY-DURATION CURVE = 0.5491524 COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 100.00 1-HOUR INTENSITY(INCH/HOUR) = 1.200 SLOPE OF INTENSITY DURATION CURVE = 0.5492
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED FOR RATIONAL METHOD NOTE: CONSIDER ALL CONFLUENCE STREAM COMBINATIONS
FOR ALL DOWNSTREAM ANALYSES
*USER-DEFINED STREET-SECTIONS FOR COUPLED PIPEFLOW AND STREETFLOW MODEL* HALF- CROWN TO STREET-CROSSFALL: CURB GUTTER-GEOMETRIES: MANNING
WIDTH CROSSFALL IN- / OUT-/PARK- HEIGHT WIDTH LIP HIKE FACTOR NO. (FT) (FT) SIDE / SIDE/ WAY (FT) (FT) (FT) (FT) (n) === ===== ========= ================= ====== ===== ====== ===== ======= 1 30.0 20.0 0.018/0.018/0.020 0.67 2.00 0.0313 0.167 0.0150 GLOBAL STREET FLOW-DEPTH CONSTRAINTS:
1. Relative Flow-Depth = 0.00 FEET
as (Maximum Allowable Street Flow Depth) - (Top-of-Curb)
2. (Depth)*(Velocity) Constraint = 6.0 (FT*FT/S)
*SIZE PIPE WITH A FLOW CAPACITY GREATER THAN
OR EQUAL TO THE UPSTREAM TRIBUTARY PIPE.*
**************************************************************************** FLOW PROCESS FROM NODE 1.00 TO NODE 2.00 IS CODE = 21 ---------------------------------------------------------------------------- >>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS COMMERCIAL
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW-LENGTH(FEET) = 292.06
UPSTREAM ELEVATION(FEET) = 882.24
DOWNSTREAM ELEVATION(FEET) = 878.78
ELEVATION DIFFERENCE(FEET) = 3.46
TC = 0.303*[( 292.06**3)/( 3.46)]**.2 = 7.129
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.865
COMMERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .8879
SOIL CLASSIFICATION IS "C"
SUBAREA RUNOFF(CFS) = 11.94
TOTAL AREA(ACRES) = 3.48 TOTAL RUNOFF(CFS) = 11.94 **************************************************************************** FLOW PROCESS FROM NODE 2.00 TO NODE 2.00 IS CODE = 10 ---------------------------------------------------------------------------- >>>>>MAIN-STREAM MEMORY COPIED ONTO MEMORY BANK # 1 <<<<< ============================================================================ **************************************************************************** FLOW PROCESS FROM NODE 2.00 TO NODE 2.00 IS CODE = 13 ---------------------------------------------------------------------------- >>>>>CLEAR THE MAIN-STREAM MEMORY<<<<<
============================================================================ **************************************************************************** FLOW PROCESS FROM NODE 27.20 TO NODE 27.30 IS CODE = 21 ---------------------------------------------------------------------------- >>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS SINGLE FAMILY (1/4 ACRE)
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW-LENGTH(FEET) = 2313.53
UPSTREAM ELEVATION(FEET) = 910.75
DOWNSTREAM ELEVATION(FEET) = 881.40
ELEVATION DIFFERENCE(FEET) = 29.35
TC = 0.393*[( 2313.53**3)/( 29.35)]**.2 = 20.845
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 2.145
SINGLE-FAMILY(1/4 ACRE LOT) RUNOFF COEFFICIENT = .8017
SOIL CLASSIFICATION IS "C"
SUBAREA RUNOFF(CFS) = 22.71
TOTAL AREA(ACRES) = 13.21 TOTAL RUNOFF(CFS) = 22.71 +--------------------------------------------------------------------------+ | SUBAREA O-1 | | | | | +--------------------------------------------------------------------------+ **************************************************************************** FLOW PROCESS FROM NODE 27.30 TO NODE 27.30 IS CODE = 10 ---------------------------------------------------------------------------- >>>>>MAIN-STREAM MEMORY COPIED ONTO MEMORY BANK # 2 <<<<< ============================================================================ **************************************************************************** FLOW PROCESS FROM NODE 27.30 TO NODE 27.30 IS CODE = 13 ---------------------------------------------------------------------------- >>>>>CLEAR THE MAIN-STREAM MEMORY<<<<<
============================================================================ **************************************************************************** FLOW PROCESS FROM NODE 3.00 TO NODE 4.00 IS CODE = 21 ---------------------------------------------------------------------------- >>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS COMMERCIAL
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW-LENGTH(FEET) = 413.62
UPSTREAM ELEVATION(FEET) = 882.78
DOWNSTREAM ELEVATION(FEET) = 876.31
ELEVATION DIFFERENCE(FEET) = 6.47
TC = 0.303*[( 413.62**3)/( 6.47)]**.2 = 7.751
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 3.692
COMMERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .8874
SOIL CLASSIFICATION IS "C"
SUBAREA RUNOFF(CFS) = 11.34
TOTAL AREA(ACRES) = 3.46 TOTAL RUNOFF(CFS) = 11.34 **************************************************************************** FLOW PROCESS FROM NODE 4.00 TO NODE 4.00 IS CODE = 11 ---------------------------------------------------------------------------- >>>>>CONFLUENCE MEMORY BANK # 1 WITH THE MAIN-STREAM MEMORY<<<<< ============================================================================ ** MAIN STREAM CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 11.34 7.75 3.692 3.46
LONGEST FLOWPATH FROM NODE 3.00 TO NODE 4.00 = 413.62 FEET. ** MEMORY BANK # 1 CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 11.94 7.13 3.865 3.48
LONGEST FLOWPATH FROM NODE 1.00 TO NODE 4.00 = 292.06 FEET. ** PEAK FLOW RATE TABLE **
STREAM RUNOFF Tc INTENSITY
NUMBER (CFS) (MIN.) (INCH/HOUR)
1 22.37 7.13 3.865
2 22.74 7.75 3.692
COMPUTED CONFLUENCE ESTIMATES ARE AS FOLLOWS:
PEAK FLOW RATE(CFS) = 22.74 Tc(MIN.) = 7.75
TOTAL AREA(ACRES) = 6.9
**************************************************************************** FLOW PROCESS FROM NODE 4.00 TO NODE 4.00 IS CODE = 11 ---------------------------------------------------------------------------- >>>>>CONFLUENCE MEMORY BANK # 2 WITH THE MAIN-STREAM MEMORY<<<<< ============================================================================ ** MAIN STREAM CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 22.37 7.13 3.865 6.94
2 22.74 7.75 3.692 6.94
LONGEST FLOWPATH FROM NODE 3.00 TO NODE 4.00 = 413.62 FEET. ** MEMORY BANK # 2 CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 22.71 20.84 2.145 13.21
LONGEST FLOWPATH FROM NODE 27.20 TO NODE 4.00 = 2313.53 FEET. ** PEAK FLOW RATE TABLE **
STREAM RUNOFF Tc INTENSITY
NUMBER (CFS) (MIN.) (INCH/HOUR)
1 30.14 7.13 3.865
2 31.19 7.75 3.692
3 35.92 20.84 2.145
COMPUTED CONFLUENCE ESTIMATES ARE AS FOLLOWS:
PEAK FLOW RATE(CFS) = 35.92 Tc(MIN.) = 20.84
TOTAL AREA(ACRES) = 20.1
============================================================================ END OF STUDY SUMMARY:
TOTAL AREA(ACRES) = 20.1 TC(MIN.) = 20.84 PEAK FLOW RATE(CFS) = 35.92
*** PEAK FLOW RATE TABLE ***
Q(CFS) Tc(MIN.)
1 30.14 7.13
2 31.19 7.75
3 35.92 20.84
============================================================================ ============================================================================
END OF RATIONAL METHOD ANALYSIS
Hydrology Report Prepared by
Riverside, California KHR Associates
Appendix 1.2
Pre-Development Hydrology Calculations:
6th Street Off-Site Runoff
____________________________________________________________________________ ****************************************************************************
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT (RCFC&WCD) 1978 HYDROLOGY MANUAL
(c) Copyright 1982-2016 Advanced Engineering Software (aes) (Rational Tabling Version 23.0)
Release Date: 07/01/2016 License ID 1681
Analysis prepared by:
KHR Associates
17530 Von Karman Avenue
Irvine, CA 92626
************************** DESCRIPTION OF STUDY ************************** * IRON LOFTS * * PRE-DEVELOPMENT HYDROLOGY - 6TH STREET OFF-SITE RUNOFF * * 10-YEAR STORM EVENT * ************************************************************************** FILE NAME: 6TH-FR.DAT
TIME/DATE OF STUDY: 17:26 08/02/2024
---------------------------------------------------------------------------- USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
---------------------------------------------------------------------------- USER SPECIFIED STORM EVENT(YEAR) = 10.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 4.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE = 0.95 10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 2.140
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = 0.800
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 3.210
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = 1.200
SLOPE OF 10-YEAR INTENSITY-DURATION CURVE = 0.5491525
SLOPE OF 100-YEAR INTENSITY-DURATION CURVE = 0.5491524 COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 10.00 1-HOUR INTENSITY(INCH/HOUR) = 0.808 SLOPE OF INTENSITY DURATION CURVE = 0.5492
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED FOR RATIONAL METHOD NOTE: CONSIDER ALL CONFLUENCE STREAM COMBINATIONS
FOR ALL DOWNSTREAM ANALYSES
*USER-DEFINED STREET-SECTIONS FOR COUPLED PIPEFLOW AND STREETFLOW MODEL* HALF- CROWN TO STREET-CROSSFALL: CURB GUTTER-GEOMETRIES: MANNING
WIDTH CROSSFALL IN- / OUT-/PARK- HEIGHT WIDTH LIP HIKE FACTOR NO. (FT) (FT) SIDE / SIDE/ WAY (FT) (FT) (FT) (FT) (n) === ===== ========= ================= ====== ===== ====== ===== ======= 1 30.0 20.0 0.018/0.018/0.020 0.67 2.00 0.0313 0.167 0.0150 GLOBAL STREET FLOW-DEPTH CONSTRAINTS:
1. Relative Flow-Depth = 0.00 FEET
as (Maximum Allowable Street Flow Depth) - (Top-of-Curb)
2. (Depth)*(Velocity) Constraint = 6.0 (FT*FT/S)
*SIZE PIPE WITH A FLOW CAPACITY GREATER THAN
OR EQUAL TO THE UPSTREAM TRIBUTARY PIPE.*
**************************************************************************** FLOW PROCESS FROM NODE 26.10 TO NODE 26.20 IS CODE = 21 ---------------------------------------------------------------------------- >>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS SINGLE FAMILY (1/4 ACRE)
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW-LENGTH(FEET) = 2313.53
UPSTREAM ELEVATION(FEET) = 910.75
DOWNSTREAM ELEVATION(FEET) = 881.40
ELEVATION DIFFERENCE(FEET) = 29.35
TC = 0.393*[( 2313.53**3)/( 29.35)]**.2 = 20.845
10 YEAR RAINFALL INTENSITY(INCH/HOUR) = 1.444
SINGLE-FAMILY(1/4 ACRE LOT) RUNOFF COEFFICIENT = .7681
SOIL CLASSIFICATION IS "C"
SUBAREA RUNOFF(CFS) = 14.65
TOTAL AREA(ACRES) = 13.21 TOTAL RUNOFF(CFS) = 14.65 +--------------------------------------------------------------------------+ | SUBAREA O-1 TO PROPOSED CITY CATCH BASIN | | | | | +--------------------------------------------------------------------------+ ============================================================================ END OF STUDY SUMMARY:
TOTAL AREA(ACRES) = 13.2 TC(MIN.) = 20.84 PEAK FLOW RATE(CFS) = 14.65
============================================================================ ============================================================================
END OF RATIONAL METHOD ANALYSIS
____________________________________________________________________________ ****************************************************************************
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM BASED ON
RIVERSIDE COUNTY FLOOD CONTROL & WATER CONSERVATION DISTRICT (RCFC&WCD) 1978 HYDROLOGY MANUAL
(c) Copyright 1982-2016 Advanced Engineering Software (aes) (Rational Tabling Version 23.0)
Release Date: 07/01/2016 License ID 1681
Analysis prepared by:
KHR Associates
17530 Von Karman Avenue
Irvine, CA 92626
************************** DESCRIPTION OF STUDY ************************** * IRON LOFTS * * PRE-DEVELOPMENT HYDROLOGY - 6TH STREET OFF-SITE RUNOFF * * 100-YEAR STORM EVENT * ************************************************************************** FILE NAME: 6TH-FR.DAT
TIME/DATE OF STUDY: 17:26 08/02/2024
---------------------------------------------------------------------------- USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
---------------------------------------------------------------------------- USER SPECIFIED STORM EVENT(YEAR) = 100.00
SPECIFIED MINIMUM PIPE SIZE(INCH) = 4.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE = 0.95 10-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 2.140
10-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = 0.800
100-YEAR STORM 10-MINUTE INTENSITY(INCH/HOUR) = 3.210
100-YEAR STORM 60-MINUTE INTENSITY(INCH/HOUR) = 1.200
SLOPE OF 10-YEAR INTENSITY-DURATION CURVE = 0.5491525
SLOPE OF 100-YEAR INTENSITY-DURATION CURVE = 0.5491524 COMPUTED RAINFALL INTENSITY DATA:
STORM EVENT = 100.00 1-HOUR INTENSITY(INCH/HOUR) = 1.200 SLOPE OF INTENSITY DURATION CURVE = 0.5492
RCFC&WCD HYDROLOGY MANUAL "C"-VALUES USED FOR RATIONAL METHOD NOTE: CONSIDER ALL CONFLUENCE STREAM COMBINATIONS
FOR ALL DOWNSTREAM ANALYSES
*USER-DEFINED STREET-SECTIONS FOR COUPLED PIPEFLOW AND STREETFLOW MODEL* HALF- CROWN TO STREET-CROSSFALL: CURB GUTTER-GEOMETRIES: MANNING
WIDTH CROSSFALL IN- / OUT-/PARK- HEIGHT WIDTH LIP HIKE FACTOR NO. (FT) (FT) SIDE / SIDE/ WAY (FT) (FT) (FT) (FT) (n) === ===== ========= ================= ====== ===== ====== ===== ======= 1 30.0 20.0 0.018/0.018/0.020 0.67 2.00 0.0313 0.167 0.0150 GLOBAL STREET FLOW-DEPTH CONSTRAINTS:
1. Relative Flow-Depth = 0.00 FEET
as (Maximum Allowable Street Flow Depth) - (Top-of-Curb)
2. (Depth)*(Velocity) Constraint = 6.0 (FT*FT/S)
*SIZE PIPE WITH A FLOW CAPACITY GREATER THAN
OR EQUAL TO THE UPSTREAM TRIBUTARY PIPE.*
**************************************************************************** FLOW PROCESS FROM NODE 26.10 TO NODE 26.20 IS CODE = 21 ---------------------------------------------------------------------------- >>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
ASSUMED INITIAL SUBAREA UNIFORM
DEVELOPMENT IS SINGLE FAMILY (1/4 ACRE)
TC = K*[(LENGTH**3)/(ELEVATION CHANGE)]**.2
INITIAL SUBAREA FLOW-LENGTH(FEET) = 2313.53
UPSTREAM ELEVATION(FEET) = 910.75
DOWNSTREAM ELEVATION(FEET) = 881.40
ELEVATION DIFFERENCE(FEET) = 29.35
TC = 0.393*[( 2313.53**3)/( 29.35)]**.2 = 20.845
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 2.145
SINGLE-FAMILY(1/4 ACRE LOT) RUNOFF COEFFICIENT = .8017
SOIL CLASSIFICATION IS "C"
SUBAREA RUNOFF(CFS) = 22.71
TOTAL AREA(ACRES) = 13.21 TOTAL RUNOFF(CFS) = 22.71 +--------------------------------------------------------------------------+ | SUBAREA O-1 TO PROPOSED CITY CATCH BASIN | | | | | +--------------------------------------------------------------------------+ ============================================================================ END OF STUDY SUMMARY:
TOTAL AREA(ACRES) = 13.2 TC(MIN.) = 20.84 PEAK FLOW RATE(CFS) = 22.71
============================================================================ ============================================================================
END OF RATIONAL METHOD ANALYSIS
Hydrology Report Prepared by
Riverside, California KHR Associates
Appendix 2
Post-Development Hydrology Map