TX FLAP 200(1) Final Hydraulics Report-Signed.pdf

Lewisville Lake Environmental Learning Area (LLELA)

TX FLAP 200(1)

Final Hydraulics Report

Federal Highway Administration

Eastern Federal Lands Highway Division

Prepared by

HDR Engineering, Inc.

08/26/2024

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T A

TE OF TEXA

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P R

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SIONAL ENG

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E R100194

COLIN G. BLANKENSHIP

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09/03/24

EFLHD | LLELA TX FLAP 200(1)

TABLE OF CONTENTS

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(303) 764-1520

TABLE OF CONTENTS

Page

TABLE OF CONTENTS ............................................................................................................................. I

INTRODUCTION

Scope and Purpose

Project Location

Project Description

Drainage Criteria

Exceptions to Criteria

HYDROLOGY

Drainage Basin Descriptions

Existing Conditions

Proposed Conditions

Rational Method

FEMA

DESIGN DISCUSSION

Existing Structures

Hydraulic Analysis

Water Quality

RECOMMENDED DESIGN

SUMMARY

REFERENCES

Appendices

Appendix A. Maps

Appendix B. Hydrology

Appendix C. Hydraulics

Introduction hdrinc.com 1670 Broadway Suite 3400 Denver, CO 80202-4824 1

Scope and Purpose The Lewisville Lake Environmental Learning Area (LLELA) project will improve the roadways accessing LLELA. The work consists of improvements to two roadways, Jones Street (from

North Cowan Avenue to the intersection with North Kealy Avenue) and North Kealy Avenue

(from its intersection with Jones Street to the northern limit of the Kansas City Southern Railroad

Right-of-Way). Both roadways will be widened to a 36-foot wide concrete pavement roadway section with bike lanes, and curb and gutter on both sides of the roadway. A 10-foot wide meandering path will be constructed on the north side of Jones Street and on the east side of

North Kealy Avenue.

Drainage improvements for the project include two enclosed storm systems to capture roadway runoff along Jones Street and a series of curb cuts and gutter pans along Kealy Avenue to convey runoff into the existing drainage ditches south of the project.

Project Location The project is located northwest of Dallas in Lewisville, Texas, Denton County. LLELA is accessed by Jones Street from the west or North Kealy Avenue from the south. Figure 1 and 2 gives a regional and local location map for the project.

Figure 1 Regional Project Location (Google Earth) hdrinc.com 1670 Broadway Suite 3400 Denver, CO 80202-4824 2

Figure 2 Local Project Location (Google Earth)

Project Description Jones Street is a 2.2 mile section of urban minor arterial with heavy traffic that serves industrial properties, utility corridors, Army Corp. of Engineer’s property and LLELA. The existing roadway section is one variable width 11 to 12 foot lane each direction.

North Kealy Avenue is 0.33 miles of urban minor arterial that also serves industrial properties, utility corridors, Army Corps of Engineer’s property and LLELA. The existing roadway section is one 12 foot lane each direction.

The proposed roadway section is 2-12-foot lanes with 6-foot shoulders and 6-inch curb. At

Jones Street Station 12+15 the improvements begin with an attached 5-foot sidewalk that transitions to a detached 10-foot aggregate trail at Station 14+50.

Drainage Criteria Drainage design for TX FLAP 200(1) has combined criteria outlined from Federal Lands

Highway (FLH) Project Development and Design Manual (PDDM) and local criteria from City of

Lewisville, Texas Drainage Criteria Manual (DCM). Criteria used consists primarily of City of

Lewisville criteria as they are the owner and will perform maintenance. Some exceptions to criteria are being allowed on this project due to the constrained site area. Design variance decisions have been discussed with the City of Lewisville and have been documented in the the

Exception to Criteria section.

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Drainage criteria was developed for an urban minor arterial road. Table 1 summarizes the roadway hydrologic and hydraulic criteria.

Table 1 Summary of Roadway Drainage Criteria

Design Frequency

Design 10-year design, 100-year check

Hydrologic Method Rational method : allowable for basins up to 100 acres

Roadway Conveyance

Flow Depth Top of curb (6 inches)

Allowable Spread 10-year: 9 feet allowable spread (including shoulder)

100-year: 12 feet allowable spread

Inlets

Allowable Types City of Lewisville Standard Storm Drain Curb Inlet Detail 9.4

Allowable Sizes 5 foot, 10 foot (Curb Opening Length)

Pipes

Material Reinforced Concrete Pipe (RCP)

Slope Minimum 0.3%

Velocity Minimum 3 fps flowing full

Maximum 12 fps

Size Minimum 18 inches

Hydraulic grade line 10-year HGL inside of pipes, 100-year HGL below proposed surface

End treatments Headwall, City Type A Detail 9.20a or Type B Detail 8.20b

Safety End Treatment Type II, City Detail 9.23

Outlet protection Safety End Treatment, City Detail 9.23 (up to 30” RCP)Riprap apron, EFLHD Standard E251-01

Clean out access

Intervals not to exceed 600 feet for pipe 30 inches in diameter or smaller

Pipes greater than 30 inches not to exceed 1,200 feet

Exceptions to Criteria

Site constraints have limited the design of the storm system and a variance to DCM was agreed upon with the City.

1. The minimum pipe slope per the DCM is 0.45% where possible. There is minimal elevation change across the project and pipe slope of 0.45% is unattainable in some locations including low points/outfalls. A minimum pipe slope of 0.3% will be allowed by the City where site conditions are restrictive to attaining 0.45%.

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2. Hydraulics of pipes per the DCM requires the hydraulic grade line (HGL) to be 2 feet below finished grade. The storm system is shallow at many locations including low points which limits the pipe size, depth and slope. The City will allow the HGL for the design storm (10-year) to be contained within the pipe and the major storm (100-year) below finished grade.

3. The City has directed to connect the Jones Street System 1 (JS1) to an existing storm south of Jones Street at station 16+08 Rt. The existing system includes a series of grate inlets connected by 18-inch CMP. JS1 connects to the first existing inlet with a 24-inch

RCP. Per discussions with the City the proposed system will be placed with what meets pipe hydraulic criteria assuming the existing system will be replaced in the future.

Hydrology

Drainage Basin Descriptions

Existing Conditions

Basins along Jones Street are roadway basins. In the existing condition, runoff sheet flows off and away from the road into open vegetated fields. There are no defined swales and the terrain is flat. On the north, runoff drains through a vegetated, flat, and undeveloped area. This area is owned by the United States Army Corps of Engineers (USACE). Runoff on the south drains through vegetated undeveloped utility easement that include private lots and City property.

Runoff drains west to east from N Cowan Avenue station 12+00 east to the low point at station

18+00. Then east to west from the a high point at station 25+00 to the low point at station

18+00. The two low points then convey runoff through more defined swale either to the north or south. The low points are located on Jones Street at stations 18+04 and 31+36.

Along N Kealy Avenue runoff is a combination of roadway and offsite basins. On the east side roadway basins drain toward the undeveloped area to the east, part of LLELA. Runoff sheet flows through this area as there are no defined swales and the terrain is flat. On the west roadway runoff drains to an open swale between the road and adjacent properties. Offsite basins also contribute runoff to the swale. Runoff is conveyed through swales and driveway culverts from north to south and captured in a drop inlet and then outfalls to the drainage ditch that runs along the railroad.

Proposed Conditions

Basins along Jones Street are roadway basins capturing runoff between the proposed curb and gutter. Roadway basins drain east and west following the profile of the road. Offsite runoff does not drain onto the roadway along Jones Street.

Basins along N Kealy Avenue include areas of undeveloped land west of the road draining onto the road and the roadway basins defined by the proposed curb and gutter. The west half of N

Kealy Avenue drains to a series of gutter pans across driveways, ditches, and driveway culverts

Hydrology hdrinc.com 1670 Broadway Suite 3400 Denver, CO 80202-4824 5 that drain south ultimately to outfall into a large drainageway south of the site. The east half of N

Kealy Avenue drains to proposed chase drains under the proposed trail to discharge small amounts of water offsite toward the USACE property matching existing runoff conditions.

Proposed hydrology and basin maps are included in Appendix B.

Rational Method

Basins are less than 100 acres and peak flows were determined using the rational method per the DCM.

Soil information was obtained from the Natural Resources Conservation Service (NRCS) Web

Soil Survey. Soil reports are included in Appendix A. Soils consist primarily of Hydrologic Soil

Group D, fine sandy loam and clay loam. These soils have a slow rate of infiltration and high rate of runoff.

Point rainfall data Table 2-1, from the DCM was compared with current data from the National

Oceanic and Atmospheric Administration (NOAA). Current data was slightly higher and therefore these values were used. Table 2 provides NOAA Atlas 14, Volume 11, Version 2 point rainfall depths for the project area. Data from the DCM, Table 2-1 Point Rainfall and Figure 2-4

Rainfall Curves, and NOAA Precipitation Frequency Data Server Point Precipitation Frequency

Estimates are included in Appendix B.

Table 2 Precipitation

Duration minutes

Design 10-Year

Recurrence Interval inches/hour

Major 100-Year

Recurrence Interval inches/hour

5 8.3 12

10 6.7 9.6

15 5.5 7.9

30 3.8 5.4

60 2.5 3.6

Runoff coefficient values were determined from DCM Table 2-4 Frequency Factor Coefficients for Adjustment of the Rational Method C Value and Table 2-5 Rational Method Runoff

Coefficients for 5-year Frequency Storm from DCM Section 2 Runoff. The land use categories include streets/concrete and adjacent industrial districts/ light areas and undeveloped areas/clay soil/woodlands. Coefficients from DCM Table 2-5 were adjusted for the 100-year frequency using Table 2-4. Runoff coefficients for these land uses are summarized in Table 3. Runoff coefficient adjustment factor is applied to storm events over the 25-year frequency. There were no adjustments to C values for the 10-year.

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Table 3 100-Year Runoff Coefficients

Land Use Basin slopes

1% to 3.5%

Frequency Factor

Cf

Adjusted

Runoff Coefficient

Industrial Districts/

Light Areas

0.65 1.25 0.81

Streets, Asphaltic 0.85 1.25 1.0

Lawn Areas, Clay Soil, woodlands

0.18 1.25 0.23

Time of concentration (tc) was determined with equations from the DCM and FHWA HEC-22

Chapter 3 Section 3.2.2.3. Initial overland flow uses equation (DCM 2-9) T = Dt/60V where T is overland flow time in minutes, Dt is flow distance in feet and V is average velocity of runoff flow in feet per second (fps). DCM Figure 2-5 Average Velocities for Estimating Travel Time for

Overland Flow was used in determining average velocity. Shallow concentrated flow was determined using HEC-22 equation 3-4 V=KukSp 0.5 where Ku is a coefficient equal to 3.28 in

English units, V is velocity in fps, k is an intercept coefficient from HEC-22 Table 3-3 and Sp is slope in percent. HEC-22 references are included in Appendix B. Rational calculations are also included in Appendix B.

FEMA

The project is located below Lewisville Lake but is not located within a Special Flood Hazard

Area (SFHA). FEMA Flood Insurance Rate Map (FIRM) Map Number 48121C0555G shows the limits of the SFHA within the area, this is included in Appendix A. Figure 3 shows an overlay of

FEMA Flood Hazard Areas on Google Earth.

Design Discussion hdrinc.com 1670 Broadway Suite 3400 Denver, CO 80202-4824 7

Figure 3 FEMA Flood Hazard Zones

Existing Structures Existing structures are located along Kealy Avenue. These include existing curb inlets, drop inlets and driveway culverts. None of the existing infrastructure will remain in the proposed design.

The City provided plans for the North Side Pump Station for 740 Service Area Project No. 5143, October 1999. These plans provided some information on the existing inlet that JS1 will connect

to. This storm sewer system is located on the east side of the water treatment plant. Plans show a 6-inch PVC line connecting to what is labeled on the Drainage and Erosion Control Plan K01 as JS1-CB1 labeled a 48-inch CMP inlet. The profile provides a ground elevation of 525.24+/-with an invert in on the west for the 6-inch drain 526.46. The invert elevation out is not provided, but as drawn in the profile is 525.0 +/-. The pipe out to the south is not labeled, as drawn is shown as a 12 or 18-inch diameter pipe. City Utilities Group provided GIS data that shows JS1-

CB1 ground elevation 531.04 and flowline (FL) of 526.05. GIS data was provided for each of the four inlets. Project survey has identified the existing pipe as an 18-inch CMP. The survey was unable to access each inlet to obtain invert elevations.

Hydraulic Analysis Hydraulic analysis is based on criteria outlined in the DCM Sections 3 through 6. The proposed design includes curb and gutter along the entirety of Jones Street to N Kealy Avenue station

39+25. At station 39+25 the curb ends on the right/west side of N Kealy Avenue and transitions to a concrete swale at the edge of shoulder, across driveways and roadside ditch with driveway hdrinc.com 1670 Broadway Suite 3400 Denver, CO 80202-4824 8 culverts. City of Lewisville Standard Curb Inlets, Detail 9.4, will be used and have been placed in roadway sumps and locations based on spread requirements. Spread and inlet calculations were completed using equations from DCM Section 4-Strom Drain Inlets. Inlet capacity has been determined using the equation for inlets in sag and inlets on grade without gutter depression for curb opening inlets.

DCM Section 4.03.A equation for inlet capacity in sag is Q=3.0y3/2 L where Q is capacity in cfs of curb opening, y is head at the inlet in feet, L is length of opening through which water enters the inlet. DCM Figure 4.1 a rating curve developed from this equation with depth of gutter flow and capacity per foot of inlet shall also be used. Pages from the DCM are included in Appendix C.

DCM Section 4.04 Inlets on Grade without Gutter Depression/A. Curb Opening Inlets

(Undepressed) is used for on-grade inlet capacity per Figures 4-2 Ration of Intercepted to Total

Flow Inlets on Grade and 4-3 y=depth of Flow in Approach Gutter. Both Figures are included in

Appendix C.

Spreadsheets were developed using these equations and charts to determine inlet capacity.

FlowMaster was used to determine gutter capacity and depth of flow at inlets to use with the inlet capacity calculations. Spread and inlet capacity workbooks and standard details for curb inlets have been included in Appendix C.

Hydraulic analysis for the storm sewer system pipe capacity was completed in Bentley InRoads

Storm and Sanitary V8i (SELECTseries2). Per DCM criteria, the minimum pipe diameter is 18-inch (or equivalent) RCP pipe. Based on discussions with the City the minimum pipe slope that will be allowed is 0.3% due to constrained vertical clearance.

The hydraulic analysis for the 10-year for JS1 used a tailwater assuming the downstream system was full and was set at the rim elevation of JS1-CB1, elevation 531. Coordination with the City during regular check-in meetings discussed the connection and the contraints of the proposed connection being a 24-inch RCP to an existing downstream pipe diameter of 18-inches. The City has advised to connect the proposed storm line, JS1, to the existing storm sewer and is aware of the pipe difference. The replacement of the existing system is outside the scope of this project but could be replaced in the future. To provide an adequate system for the project needs the proposed system will be as required and designed with this tailwater condition and the following assumptions.

• The area draining to the existing grate inlets is conveyed through much larger areas with heavy vegetation resulting in a longer time to peak.

• The existing storm sewer may be replaced in the future.

The hydraulic analysis for the 10-year for JS2 used an open outfall because it drains to an open field with no defined downstream ditch.

Hydraulic calculations and reports are included in Appendix C.

Recommended Design hdrinc.com 1670 Broadway Suite 3400 Denver, CO 80202-4824 9

Chase drains were designed using Bentley FlowMaster CONNECT Edition. Sidewalk drains were checked for adequate conveyance capacity by modeling a 1.5 feet x 0.5 foot concrete rectangular channels. Calculations are included in Appendix C.

Riprap outlet protection is being proposed at culvert outlets and curb cuts to dissipate energy and minimize scour and erosion. Riprap outlet protection has been designed following FHWA

HEC-15 equations. Calculations included in Appendix C.

Water Quality The project is located within a municipal separate storm sewer (MS4) area. Water quality will be developed to meet the Texas Commission on Environmental Quality (TCEQ) General Permit

TXR040000. The area of disturbance exceeds 5 acres for this project and will require a

Stormwater Pollution Prevention Plan (SWPPP) and a Notice of Intent (NOI) be completed for the site. No permanent post construction best management practices (BMPs) are required by the General Permit other than the re-establishment of vegetation. Erosion control measures will be used during construction, BMPs will be developed by the contractor but are shown on

Drainage and Erosion Control Plans for information only.

Recommended Design The proposed design consists of two enclosed drainage systems along Jones Street and a combination of gutter pans and curb cuts along N Kealy Avenue.

The drainage system on Jones Street (Jones System 1) runs parallel to Jones Street from the west project limit at station 13+93 to station 33+35 being the high points along this roadway section. This is an enclosed storm system with a series of City of Lewisville curb inlets, 5-foot or

10-foot opening. The storm system outfalls at inlet JS1-IN4 Station 16+08 Right. The proposed system will connect to an existing system south of Jones Street near the water treatment plant.

The existing inlet at 16+08, 132 Right will be replaced with a new grate inlet, JS1-CB1, to accommodate the pipe configuration. The as-builts provided by the City identify a pipe in on east and west sides of the inlet and pipe out on the south. Survey was unable to capture all invert elevations of the system and should be verified prior to construction. Per the City’s direction, all runoff collected in Jones System 1 (JS1) will be discharged into the existing system.

The east drainage system on Jones Street (Jones System 2) runs parallel along Jones Street to the east and captures runoff from the highpoint at station 25+00 to the intersection of Jones

Street and N Kealy Avenue. Runoff for this section of the Poject is also collected in City of

Lewisville curb inlets. The storm system outfalls at station 39+12 Left toward the Army Corp property on the east side of N Kealy Avenue. The outfall pipe will require an easement for the end of pipe, headwall and riprap apron. The outlet protection was evaluated using FHWA

Toolbox. The recommended riprap class and dimensions were smaller than the standard detail.

Summary hdrinc.com 1670 Broadway Suite 3400 Denver, CO 80202-4824 10

JS2 riprap apron will use the more conservative recommendations and use Class 2 riprap with dimensions following EFL Standard Detail E-215.

The runoff on N Kealy Avenue is being handled differently for the east and west sides of the road. The runoff collected in the curb and gutter on the west side of the road will drain south along the gutter line until flowing into a proposed ditch and across two reconstructed driveway access with gutter pans to outfall into an existing drainage ditch at station 43+35. From there runoff will follow existing drainage patterns to the south ultimately outfalling into the large drainageway 0.25 miles to the south along the railroad tracks. The runoff on the east side of N

Kealy Avenue is conveyed from the roadway through two proposed 1.5 foot width by 6-inch heigh opening sidewalk drains with a riprap pad 2 feet wide by 2 feet long and thickness of one foot using Class 1 riprap. Runoff will drain east following existing offsite flow patterns.

Summary The stormwater runoff for the proposed project consists of all roadway runoff and is captured and conveyed in two enclosed proposed storm sewer systems along Jones Street. Runoff along

N Kealy Avenue is captured in inlets, concrete pans and curb cuts. Existing drainage patterns are maintained. Exceptions to the City of Lewisville drainage criteria is required due to site constraints.

No permanent water quality measures are required per the General Permit but temporary erosion control BMPs will be used during construction. The appropriate permits including the

SWPPP, NOI, and Texas Commission on Environmental Quality (TCEQ) General Permit

TXR040000 will be completed by the contractor and submitted prior to construction.

References hdrinc.com 1670 Broadway Suite 3400 Denver, CO 80202-4824 11

References Central Federal Lands Highway Division, "Project Development and Design Manual", Chapter 7

Hydrology and Hydraulics, December 2012.

City of Lewisville, “Drainage Criteria Manual”, Chapter 22 Drainage, Flood Control and Erosion

Control, April 1988.

City of Lewisville, “Standard Construction Details”, August 2007.

Shimek, Jacobs & Finklea, L.L.P Consulting Engineers, “City of Lewisville, Texas Improvements to Water Treatment Plant North Side Pump Station for 740 Service Area Project No. 5143”, October, 1999.

Texas Commission on Environmental Quality, “General Permit to Discharge Under the Texas

Pollutant Discharge Elimination System”, January 24, 2019.

U.S. Department of Agriculture, "NRCS-Web Soil Survey", December 2011.

U.S. Department of Transportation, Federal Highway Administration, "Design of Roadside

Channel with Flexible Linings", Hydraulic Engineering Circular No. 15, September 2005.

U.S. Department of Transportation, Federal Highway Administration, "Stream Stability at

Highway Structures", Hydraulic Engineering Circular No. 20, March 2001.

EFHL | LELLA TX FLAP 200(1)

Appendix A.

Maps hdrinc.com 1670 BroadwaySuite 3400Denver, CO 80202-4824

(303) 764-15200

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Project Loction

Project Location Kealy Ave

Appendix B.

Appendix B.

52952

U

S E

R

TX

c p w w o r k in g c e n t r a l0 d

L E

L L

A

E x is t in g

B a s in

M p .d g n

STATE PROJECT

NUMBER

SHEET

TX FLAP 200(1)

EASTERN FEDERAL LANDS HIGHWAY DIVISION

FEDERAL HIGHWAY ADMINISTRATION

U.S. DEPARTMENT OF TRANSPORTATION

STATE PROJECT

NUMBER

SHEET

TX TX FLAP 200(1)

ENVIRONMENTAL LEARNING AREA

LEWISVILLE LAKE (USACE)

13+75 RT

Acres

0.82 0.32

0.81

31+50 LT

Acres

0.62 0.42

0.69

42+80 LT

Acres

0.61 0.41

0.71

3+00 LT

Acres

0.29 0.40

0.69

SCALE IN FEET

0 25' 50'

Basin ID

Acres

X.XX C10

C100

Flow Direction

Basin Boundary

J o n e s S t.

M a tc h L in e

J o n e s S t.

M a tc h L in e

Kealy Ave. Match Line 1

42+75 RT

Acres

3.55 0.21

0.94

N Kealy Ave

Jones St

Jones St

Existing Basin Map

16+25 RT

Acres

0.76 0.28

0.86

17+55 RT

Acres

0.84 0.27

0.87

19+25 RT

Acres

0.88 0.26

0.88

17+50 LT

Acres

1.11 0.43

0.68

24+50 RT

Acres

0.34 0.27

0.87

31+25 RT

Acres

0.90 0.34

0.79

K e a ly A v e

M a tc h L in e

SCALE IN FEET

0 25' 50'

13+75RT

16+75 RT

17+55 RT

19+25 RT

17+50 LT

31+50 LT

31+25 RT

3+00 LT

42+75 RT

42+80 LT

SCALE IN FEET

0 25' 50'

24+50 RT

Rational Method

Runoff Coefficients Project: TX FLAP 200(1) LELLATX FLAP 200(1) LELLA Computed: CDK Date: 4/10/2021

System Name: Proposed Hydrology Checked: SDA Date:

Sub-Basin Data

Basin ID Description Total Area (ac)

JS1-IN1 0.19 0.68 0.16 0.84 0.81 0.19 1.00 C 76.2% 0.142 0.04

JS1-IN2 0.22 0.82 0.16 0.84 0.97 0.19 1.00 C 96.4% 0.216 0.01

JS1-IN3 0.09 0.84 0.16 0.84 1.00 0.19 1.00 C 99.7% 0.087 0.00

JS1-IN4 0.09 0.84 0.16 0.84 1.00 0.19 1.00 C 99.9% 0.091 0.00

JS1-IN5 0.18 0.78 0.16 0.84 0.93 0.19 1.00 D 91.6% 0.167 0.02

JS1-IN6 0.17 0.80 0.16 0.84 0.96 0.19 1.00 D 94.6% 0.164 0.01

JS1-IN7 0.09 0.82 0.16 0.84 0.98 0.19 1.00 B 97.7% 0.08 0.00

JS1-IN8 0.10 0.75 0.16 0.84 0.90 0.19 1.00 B 87.4% 0.08 0.01

JS1-IN9 0.13 0.74 0.16 0.84 0.88 0.19 1.00 B 84.8% 0.11 0.02

JS1-IN10 0.12 0.76 0.16 0.84 0.91 0.19 1.00 B 88.9% 0.11 0.01

JS2-IN1 0.08 0.86 0.16 0.84 1.02 0.19 1.00 B 102.9% 0.08 0.00

JS2-IN2 0.09 0.77 0.16 0.84 0.92 0.19 1.00 B 89.9% 0.08 0.01

JS2-IN3 0.09 0.82 0.16 0.84 0.98 0.19 1.00 B 97.3% 0.09 0.00

JS2-IN4 0.10 0.78 0.16 0.84 0.93 0.19 1.00 B 91.2% 0.09 0.01

JS2-IN5 0.19 0.81 0.16 0.84 0.96 0.19 1.00 B 95.7% 0.18 0.01

JS2-IN6 0.19 0.79 0.16 0.84 0.94 0.19 1.00 D 92.4% 0.18 0.01

JS2-IN7 0.07 0.59 0.16 0.84 0.71 0.19 1.00 D 63.6% 0.05 0.03

JS2-IN8 0.05 0.78 0.16 0.84 0.92 0.19 1.00 D 90.5% 0.05 0.01

JS2-IN9 0.07 0.72 0.16 0.84 0.85 0.19 1.00 D 81.9% 0.06 0.01

JS2-IN10 0.12 0.70 0.16 0.84 0.84 0.19 1.00 D 79.8% 0.09 0.02

JS2-IN11 0.28 0.38 0.16 0.84 0.46 0.19 1.00 D 33.0% 0.09 0.19

JS2-IN12 0.06 0.48 0.16 0.84 0.57 0.19 1.00 D 46.9% 0.03 0.03

KS1-DP1 1.63 0.20 0.16 0.84 0.24 0.19 1.00 D 5.8% 0.09 1.54

KS1-DP2 0.05 0.82 0.16 0.84 0.98 0.19 1.00 D 97.3% 0.05 0.00

KS1-DP3 1.06 0.24 0.16 0.84 0.29 0.19 1.00 D 11.9% 0.13 0.93

KS1-DP4 0.07 0.82 0.16 0.84 0.98 0.19 1.00 D 97.4% 0.07 0.00

KS1-DP5 0.06 0.82 0.16 0.84 0.98 0.19 1.00 D 97.3% 0.06 0.00

KS1-IN1 0.27 0.33 0.16 0.84 0.39 0.19 1.00 D 24.4% 0.07 0.20

JS3-DI1 0.19 0.16 0.16 0.84 0.19 0.19 1.00 D 0.0% 0.00 0.19

JS3-A1 0.24 0.43 0.16 0.84 0.51 0.19 1.00 D 39.1% 0.09 0.15

Frequency of Storm Runoff Coefficient for Basin Slope

5 < 1% 1%-3.5% 3.5%-5.5%

25 0.53 0.68 0.84

50 0.16 0.19 0.23

100 0.84 0.84 0.84

C10

Pervious Areas

C10

Paved Areas

Hydrologic

Soils Group

Percent

Impervious

Area Impervious

(ac) Area Pervious (ac)

1.05

Table 2-5

Rational Method Runoff Coefficients for 10-year Frequency Storm

Composite

C100

1.20

1.25

Light Industrial

Lawn Areas, Clay Soils

Streets, Asphalt

Frequency Factor Cf

Table 2-4 Frequency Factor Coefficients for Adjustment of the Rational Method C Value

1.00

1.10

*C values determined from DCM, Section 2, Tables 2-4 and 2-5

C100

Pervious Areas

C100

Paved Areas

Composite

C10

Standard Form SF-1 . Time of Concentration

Project: TX FLAP 200(1) LLELA Computed: CDK Date: 4/10/2021

System Name: Proposed Hydrology Checked: SDA Date: 5/17/2021 Notes: Ku n Intensity

SUB-BASIN DATA INITIAL/OVERLAND FLOW TRAVEL TIME FINAL Tc Overland Flow 0.933 0.013 2.470

(ti) (tt) (min) Concentrated Velocity 3.28

*see Tabl 3-3 Concentrated Flow

Basin ID Description C10 Area (ac) Length (ft) Elevation 1 Elevation 2

Slope

(ft/ft) ti

(min)

Length

(ft) Elevation 1 Elevation 2

So

(ft/ft)

Intercept

Coefficient (k) Velocity

Travel

Time Tt

(min) tc = ti + tt

(min)

Travel Time=

JS1-IN1 0.69 0.76 0.19 26 546.5 545.8 0.027 1.00 327 545.8 537.4 0.026 0.9 4.8 1.12 2.13 5.0 Final Tc= Min 10 minutes or Tc if >10

JS1-IN2 0.83 0.96 0.22 91 546.2 544.0 0.024 2.20 263 544.0 537.8 0.024 0.9 4.6 0.94 3.14 5.0 Intensity 10-year storm, 60-min 2.470

JS1-IN3 0.85 1.00 0.09 26 537.8 536.9 0.035 0.93 180 536.9 533.6 0.018 0.9 4.1 0.73 1.66 5.0 Ku Overland English Units 0.933

JS1-IN4 0.85 1.00 0.09 28 537.9 537.4 0.018 1.19 180 537.4 533.9 0.019 0.92 4.2 0.71 1.90 5.0 Ku Concentrated English units 3.28

JS1-IN5 0.79 0.92 0.18 21 533.6 533.4 0.010 1.20 163 533.4 532.5 0.006 0.92 2.3 1.20 2.41 5.0 k HEC22 Table 3-3 (below)

JS1-IN6 0.81 0.95 0.17 20 533.7 533.4 0.015 1.02 171 533.4 532.2 0.007 0.92 2.5 1.12 2.15 5.0

JS1-IN7 0.83 0.98 0.09 24 537.5 536.8 0.029 0.93 185 536.8 533.7 0.017 0.92 3.9 0.79 1.72 5.0

JS1-IN8 0.77 0.87 0.10 23 537.5 536.8 0.030 0.90 183 536.8 533.8 0.016 0.92 3.9 0.79 1.68 5.0

JS1-IN9 0.75 0.85 0.13 18 540.3 539.9 0.022 0.85 199 539.9 537.2 0.014 0.92 3.5 0.93 1.79 5.0

JS1-IN10 0.78 0.89 0.12 16 540.3 540.0 0.019 0.84 212 540.0 537.2 0.013 0.92 3.5 1.01 1.85 5.0

JS2-IN1 0.87 1.03 0.08 18 540.4 540.0 0.022 0.85 164 540.0 539.0 0.006 0.92 2.4 1.16 2.01 5.0

JS2-IN2 0.78 0.90 0.09 20 540.4 540.0 0.020 0.94 153 540.0 538.7 0.008 0.92 2.8 0.91 1.85 5.0

JS2-IN3 0.83 0.97 0.09 19 538.9 538.7 0.011 1.10 230 538.7 532.4 0.027 0.92 5.0 0.77 1.87 5.0

JS2-IN4 0.79 0.91 0.10 21 538.8 538.2 0.029 0.87 222 538.2 532.4 0.026 0.92 4.9 0.76 1.62 5.0

JS2-IN5 0.82 0.96 0.19 18 534.2 534.0 0.011 1.05 328 534.0 528.8 0.016 0.92 3.8 1.44 2.48 5.0

JS2-IN6 0.80 0.92 0.19 18 534.2 534.0 0.011 1.05 329 534.0 528.4 0.017 0.92 3.9 1.39 2.44 5.0

JS2-IN7 0.61 0.64 0.07 17.7381 533.4 532.9 0.030 0.77 113 532.9 531.7 0.011 0.92 3.1 0.60 1.37 5.0

JS2-IN8 0.79 0.91 0.05 17.791 533.4 532.9 0.030 0.77 116 532.9 531.7 0.011 0.92 3.1 0.62 1.39 5.0

JS2-IN9 0.73 0.82 0.07 54.468 533.9 531.9 0.037 1.42 12 531.9 531.6 0.023 0.92 4.6 0.04 1.46 5.0

JS2-IN10 0.71 0.80 0.12 59.02 533.9 531.2 0.046 1.40 92 531.2 528.3 0.032 0.92 5.4 0.28 1.68 5.0

JS2-IN11 0.40 0.33 0.28 39 530.8 528.1 0.068 0.97 95 528.1 525.6 0.025 0.92 4.8 0.33 1.30 5.0

JS2-IN12 0.49 0.47 0.06 20 533.1 532.9 0.009 1.19 18 532.9 532.8 0.007 0.92 2.5 0.12 1.31 5.0

KS1-DP1 0.22 0.06 1.63 336.128 527.39 524.5 0.009 6.56 141 524.5 523.8 0.005 0.92 2.2 1.09 7.64 7.6

KS1-DP2 0.83 0.97 0.05 90.103 525.04 523.97 0.012 2.70 29 524.0 523.8 0.006 0.92 2.3 0.21 2.91 5.0

KS1-DP3 0.26 0.12 1.06 300 530 524 0.020 4.75 214 524.0 523.5 0.002 0.92 1.5 2.44 7.19 7.2

KS1-DP4 0.83 0.97 0.07 17.1 524.34 523.81 0.031 0.75 135 523.8 522.7 0.008 0.92 2.8 0.82 1.56 5.0

KS1-DP5 0.83 0.97 0.06 17 523.22 522.65 0.034 0.73 135 522.7 521.6 0.008 0.92 2.6 0.86 1.58 5.0

KS1-IN1 0.34 0.24 0.27 217 527.39 525 0.011 4.68 42 525.0 524.6 0.009 0.92 2.9 0.24 4.92 5.0

JS3-DI1 0.18 0.00 0.19 127 532.14 530.02 0.017 3.00 36 530.0 529.0 0.028 0.92 5.1 0.12 3.12 5.0

JS3-A1 0.44 0.39 0.24 100 530 528 0.020 2.46 50 528.0 527.0 0.020 0.92 4.3 0.19 2.65 5.0

Ku 3.28 English Units

Notes: HEC-22 Table 3-3. Intercept Coefficients for Velocity vs Slope

Overland Flow, T = Dt/60V : DCM Equation 2-9 Land Cover/Flow Regime English Unit Conversion

Velocity, Vi = DCM Figure 2-5 Average Velocities for Esimating Travel Time for Overland Flow for Lewisville, Texas Forest with heavy ground litter; hay meadow (overland flow)

Shallow Concentrated Flow Velocity, Vt = HEC22, Eqaution 3-4 V=KukSp^0.5 Trash fallow or minimum tillage cultivation; contour or strip cropped; woodland (overland flow) 0.076 0.11324

Ku English units = 3.28 Short grass pasture (overland flow) 0.152 0.22648 k HEC22 Table 3-3 Cultivated straight row (overland flow) 0.213 0.31737

Nearly bare and untilled (overland flow); alluvial fans in western mountain regions 0.274 0.40826

Grassed waterway (shallow concentrated flow) 0.305 0.45445

Unpaved (shallow concentrated flow) 0.457 0.68093

Paved area (shallow concentrated flow); small upland gullies 0.491 0.73159

0.619 0.92231 ti = (0.933/(intensity^0.4))((n*L/sqrt(slope))^0.6)

V = (3.28*k*slope^.5) tt = L/60V

Tc=ti+tt

Percent

Impervious

Total

Rational Analysis

Standard Form SF-2 . Storm Drainage System Design (Rational Method Procedure) Corridor / Design Package: TX FLAP 200(1) LELLA

System Name: Proposed Hydrology

Design Storm: 10-yr

A R

E A

S

IG

N

(n m e

A R

E A

A

C

R U

N O

F F

C O

E F

F t c

(M

IN

C .A

(A C

I

IN

H R

Q

(C

S

(1) (2) (3) (4) (5) (6) (7) (8) (9)

JS1-IN1 0 JS1-IN1 0.19 0.68 5.00 0.13 8.29 1.05

JS1-IN2 0 JS1-IN2 0.22 0.82 5.00 0.18 8.29 1.51

JS1-IN3 0 JS1-IN3 0.09 0.84 5.00 0.07 8.29 0.61

JS1-IN4 0 JS1-IN4 0.09 0.84 5.00 0.08 8.29 0.63

JS1-IN5 0 JS1-IN5 0.18 0.78 5.00 0.14 8.29 1.18

JS1-IN6 0 JS1-IN6 0.17 0.80 5.00 0.14 8.29 1.16

JS1-IN7 0 JS1-IN7 0.09 0.82 5.00 0.07 8.29 0.58

JS1-IN8 0 JS1-IN8 0.10 0.75 5.00 0.07 8.29 0.61

JS1-IN9 0 JS1-IN9 0.13 0.74 5.00 0.10 8.29 0.80

JS1-IN10 0 JS1-IN10 0.12 0.76 5.00 0.10 8.29 0.79

JS2-IN1 0 JS2-IN1 0.08 0.86 5.00 0.07 8.29 0.57

JS2-IN2 0 JS2-IN2 0.09 0.77 5.00 0.07 8.29 0.58

JS2-IN3 0 JS2-IN3 0.09 0.82 5.00 0.08 8.29 0.65

JS2-IN4 0 JS2-IN4 0.10 0.78 5.00 0.08 8.29 0.65

JS2-IN5 0 JS2-IN5 0.19 0.81 5.00 0.15 8.29 1.27

JS2-IN6 0 JS2-IN6 0.19 0.79 5.00 0.15 8.29 1.26

JS2-IN7 0 JS2-IN7 0.07 0.59 5.00 0.04 8.29 0.36

JS2-IN8 0 JS2-IN8 0.05 0.78 5.00 0.04 8.29 0.34

JS2-IN9 0 JS2-IN9 0.07 0.72 5.00 0.05 8.29 0.43

JS2-IN10 0 JS2-IN10 0.12 0.70 5.00 0.08 8.29 0.68

JS2-IN11 0 JS2-IN11 0.28 0.38 5.00 0.11 8.29 0.88

JS2-IN12 0 JS2-IN12 0.06 0.48 5.00 0.03 8.29 0.22

KS1-DP1 0 KS1-DP1 1.63 0.20 7.64 0.32 7.42 2.41

KS1-DP2 0 KS1-DP2 0.05 0.82 5.00 0.04 8.29 0.33

KS1-DP3 0 KS1-DP3 1.06 0.24 5.00 0.25 8.29 2.11

KS1-DP4 0 KS1-DP4 0.07 0.82 5.00 0.06 8.29 0.49

KS1-DP5 0 KS1-DP5 0.06 0.82 5.00 0.05 8.29 0.41

KS1-IN1 0 KS1-IN1 0.27 0.33 5.00 0.09 8.29 0.73

JS3-DI1 0 JS3-DI1 0.19 0.16 5.00 0.03 8.29 0.25

JS3-A1 0 JS3-A1 0.24 0.43 5.00 0.10 8.29 0.86

(1) Basin Description linked to C-Value Sheet (7) =Column 4 x Column 5

(2) Basin Design Point (8) =28.5*P/(10+Column 6)^0.786

(3) Enter the Basin Name from C Value Sheet (9) =Column 7 x Column 8

(4) Basin Area linked to C-Value Sheet (10) =Column 6 + Column 21

(5) Composite C linked to C-Value Sheet (11) Add the Basin Areas (7) to get the combined basin AC

(6) Time of Concentration linked to C-Value Sheet (12) =28.5*P/(10+Column 10)^0.786

(13) Sum of Qs

LOCATION

D E

S

IG

N P

O

IN

T DIRECT RUNOFF

Standard Form SF-2 . Storm Drainage System Design (Rational Method Procedure) Corridor / Design Package: TX FLAP 200(1) LELLA

System Name: Proposed Hydrology

Design Storm: 100-yr

A R

A

S

IG

N

(n m e

A R

E A

A

C

R U

N O

F F

C O

E F t c

(M

IN

C .A

(A C

I

IN

H R

Q

(C

S

(1) (2) (3) (4) (5) (6) (7) (8) (9)

JS1-IN1 1 JS1-IN1 0.19 0.81 5.00 0.15 12.0 1.81

JS1-IN2 1 JS1-IN2 0.22 0.97 5.00 0.22 12.0 2.61

JS1-IN3 JS1-IN3 0.09 1.00 5.00 0.09 12.0 1.05

JS1-IN4 JS1-IN4 0.09 1.00 5.00 0.09 12.0 1.09

JS1-IN5 JS1-IN5 0.18 0.93 5.00 0.17 12.0 2.04

JS1-IN6 JS1-IN6 0.17 0.96 5.00 0.17 12.0 1.99

JS1-IN7 JS1-IN7 0.09 0.98 5.00 0.08 12.0 1.01

JS1-IN8 JS1-IN8 0.10 0.90 5.00 0.09 12.0 1.04

JS1-IN9 JS1-IN9 0.13 0.88 5.00 0.12 12.0 1.39

JS1-IN10 JS1-IN10 0.12 0.91 5.00 0.11 12.0 1.36

JS2-IN1 JS2-IN1 0.08 1.02 5.00 0.08 12.0 0.98

JS2-IN2 JS2-IN2 0.09 0.92 5.00 0.08 12.0 1.00

JS2-IN3 JS2-IN3 0.09 0.98 5.00 0.09 12.0 1.11

JS2-IN4 JS2-IN4 0.10 0.93 5.00 0.09 12.0 1.12

JS2-IN5 JS2-IN5 0.19 0.96 5.00 0.18 12.0 2.19

JS2-IN6 JS2-IN6 0.19 0.94 5.00 0.18 12.0 2.18

JS2-IN7 JS2-IN7 0.07 0.71 5.00 0.05 12.0 0.63

JS2-IN8 JS2-IN8 0.05 0.92 5.00 0.05 12.0 0.59

JS2-IN9 JS2-IN9 0.07 0.85 5.00 0.06 12.0 0.74

JS2-IN10 JS2-IN10 0.12 0.84 5.00 0.10 12.0 1.16

JS2-IN11 JS2-IN11 0.28 0.46 5.00 0.13 12.0 1.52

JS2-IN12 JS2-IN12 0.06 0.57 5.00 0.03 12.0 0.38

KS1-DP1 KS1-DP1 1.63 0.24 7.64 0.39 10.7 4.15

KS1-DP2 KS1-DP2 0.05 0.98 5.00 0.05 12.0 0.57

KS1-DP3 KS1-DP3 1.06 0.29 5.00 0.30 12.0 3.63

KS1-DP4 KS1-DP4 0.07 0.98 5.00 0.07 12.0 0.85

KS1-DP5 KS1-DP5 0.06 0.98 5.00 0.06 12.0 0.70

KS1-IN1 KS1-IN1 0.27 0.39 5.00 0.10 12.0 1.25

JS3-DI1 JS3-DI1 0.19 0.19 5.00 0.04 12.0 0.43

JS3-A1 JS3-A1 0.24 0.51 5.00 0.12 12.0 1.47

(1) Basin Description linked to C-Value Sheet (7) =Column 4 x Column 5 13.60

(2) Basin Design Point (8) =28.5*P/(10+Column 6)^0.786

(3) Enter the Basin Name from C Value Sheet (9) =Column 7 x Column 8

(4) Basin Area linked to C-Value Sheet (10) =Column 6 + Column 21

(5) Composite C linked to C-Value Sheet (11) Add the Basin Areas (7) to get the combined basin AC

(6) Time of Concentration linked to C-Value Sheet (12) =28.5*P/(10+Column 10)^0.786

(13) Sum of Qs

LOCATION

D E

S

IG

N P

O

IN

T DIRECT RUNOFF

Lewisville, TX IDF Computed: CDK Date: 4/10/2021

NOAA Atlas 14 Checked: Date:

Time (in/hr)

(min) 2 Yr 5 Yr 10 Yr 25 Yr 50 Yr 100 Yr

5 5.86 7.2 8.29 9.77 10.9 12

6 5.630 6.920 7.960 9.390 10.470 11.520

7 5.400 6.630 7.630 9.000 10.040 11.050

8 5.160 6.350 7.310 8.620 9.600 10.570

9 4.930 6.060 6.980 8.230 9.170 10.100

10 4.7 5.78 6.65 7.85 8.74 9.62

11 4.540 5.580 6.420 7.570 8.430 9.280

12 4.370 5.380 6.190 7.290 8.120 8.930

13 4.210 5.170 5.950 7.020 7.800 8.590

14 4.040 4.970 5.720 6.740 7.490 8.240

15 3.88 4.77 5.49 6.46 7.18 7.90

16 3.800 4.670 5.380 6.330 7.030 7.730

17 3.720 4.570 5.260 6.190 6.880 7.570

18 3.640 4.470 5.150 6.060 6.730 7.400

19 3.560 4.380 5.040 5.920 6.580 7.240

20 3.480 4.280 4.920 5.790 6.430 7.070

21 3.400 4.180 4.810 5.660 6.280 6.910

22 3.320 4.080 4.700 5.520 6.130 6.740

23 3.250 3.980 4.580 5.390 5.980 6.580

24 3.170 3.880 4.470 5.250 5.830 6.410

25 3.090 3.780 4.360 5.120 5.680 6.250

26 3.010 3.680 4.240 4.990 5.530 6.080

27 2.930 3.590 4.130 4.850 5.380 5.920

28 2.850 3.490 4.020 4.720 5.230 5.750

29 2.770 3.390 3.900 4.580 5.080 5.590

30 2.69 3.29 3.79 4.45 4.93 5.42

31 2.660 3.250 3.750 4.400 4.870 5.360

32 2.630 3.210 3.700 4.350 4.820 5.300

33 2.600 3.180 3.660 4.300 4.760 5.240

34 2.560 3.140 3.610 4.240 4.700 5.170

35 2.530 3.100 3.570 4.190 4.650 5.110

36 2.500 3.060 3.530 4.140 4.590 5.050

37 2.470 3.020 3.480 4.090 4.540 4.990

38 2.440 2.990 3.440 4.040 4.480 4.930

39 2.410 2.950 3.390 3.990 4.420 4.870

40 2.380 2.910 3.350 3.940 4.370 4.800

41 2.350 2.870 3.310 3.890 4.310 4.740

42 2.310 2.830 3.260 3.830 4.250 4.680

43 2.280 2.800 3.220 3.780 4.200 4.620

44 2.250 2.760 3.170 3.730 4.140 4.560

45 2.220 2.720 3.130 3.680 4.090 4.500

46 2.190 2.680 3.090 3.630 4.030 4.430

47 2.160 2.640 3.040 3.580 3.970 4.370

48 2.130 2.610 3.000 3.530 3.920 4.310

49 2.090 2.570 2.950 3.470 3.860 4.250

50 2.060 2.530 2.910 3.420 3.800 4.190

51 2.030 2.490 2.870 3.370 3.750 4.130

52 2.000 2.450 2.820 3.320 3.690 4.060

53 1.970 2.420 2.780 3.270 3.630 4.000

54 1.940 2.380 2.730 3.220 3.580 3.940

55 1.910 2.340 2.690 3.170 3.520 3.880

56 1.880 2.300 2.650 3.120 3.470 3.820

57 1.840 2.260 2.600 3.060 3.410 3.760

58 1.810 2.230 2.560 3.010 3.350 3.690

59 1.780 2.190 2.510 2.960 3.300 3.630

60 1.75 2.15 2.47 2.91 3.24 3.57

0 10 20 30 40 50 60

R a in fa ll I n te n si ty in /h r)

Time (min)

Lewisville, TX Denton County

IDF Curve

2 Yr

5 Yr

10 Yr

25 Yr

50 Yr

100 Yr

3-9

Table 3-2. Manning's Roughness Coefficient (n) for Overland Sheet Flow.(6)

Surface Description n Smooth asphalt 0.011 Smooth concrete 0.012 Ordinary concrete lining 0.013 Good wood 0.014 Brick with cement mortar 0.014 Vitrified clay 0.015 Cast iron 0.015 Corrugated metal pipe 0.024 Cement rubble surface 0.024 Fallow (no residue) 0.05 Cultivated soils Residue cover # 20% 0.06 Residue cover > 20% 0.17 Range (natural) 0.13 Grass Short grass prairie 0.15 Dense grasses 0.24 Bermuda grass 0.41 Woods* Light underbrush 0.40 Dense underbrush 0.80 *When selecting n, consider cover to a height of about 30 mm. This is only part of the plant cover that will obstruct sheet flow.

Shallow Concentrated Flow Velocity. After short distances of at most 130 m (400 ft), sheet flow tends to concentrate in rills and then gullies of increasing proportions. Such flow is usually referred to as shallow concentrated flow. The velocity of such flow can be estimated using a relationship between velocity and slope as follows (6):

V = Ku k Sp

0.5 (3-4) where:

Ku = 1.0 (3.28 in English units) V = Velocity, m/s (ft/s) k = Intercept coefficient (Table 3-3) Sp = Slope, percent

3-10

Table 3-3. Intercept Coefficients for Velocity vs. Slope Relationship of Equation 3-4.(6)

Land Cover/Flow Regime k Forest with heavy ground litter; hay meadow (overland flow) 0.076 Trash fallow or minimum tillage cultivation; contour or strip cropped; woodland (overland flow)

0.152

Short grass pasture (overland flow) 0.213 Cultivated straight row (overland flow) 0.274 Nearly bare and untilled (overland flow); alluvial fans in western mountain regions 0.305 Grassed waterway (shallow concentrated flow) 0.457 Unpaved (shallow concentrated flow) 0.491 Paved area (shallow concentrated flow); small upland gullies 0.619

Open Channel and Pipe Flow Velocity. Flow in gullies empties into channels or pipes. Open channels are assumed to begin where either the blue stream line shows on USGS quadrangle sheets or the channel is visible on aerial photographs. Cross-section geometry and roughness should be obtained for all channel reaches in the watershed. Manning's equation can be used to estimate average flow velocities in pipes and open channels as follows:

V = (Ku/n) R2/3 S1/2 (3-5) where:

n = Roughness coefficient (see Table 3-4) V = Velocity, m/s (ft/s) R = Hydraulic radius (defined as the flow area divided by the wetted perimeter), m (ft) S = Slope, m/m (ft/ft) Ku = Units conversion factor equal to 1 (1.49 in English units)

For a circular pipe flowing full, the hydraulic radius is one-fourth of the diameter. For a wide rectangular channel (W > 10 d), the hydraulic radius is approximately equal to the depth. The travel time is then calculated as follows:

Tti = L / (60 V) (3-6) where:

Tti = Travel time for Segment I, min L = Flow length for Segment I, m (ft) V = Velocity for Segment I, m/s (ft/s)

NOAA Atlas 14, Volume 11, Version 2 Location name: Lewisville, Texas, USA* Latitude: 33.064°, Longitude: -96.9955°

Elevation: 530.01 ft**

* source: ESRI Maps

** source: USGS

POINT PRECIPITATION FREQUENCY ESTIMATES

Sanja Perica, Sandra Pavlovic, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Orlan Wilhite

NOAA, National Weather Service, Silver Spring, Maryland

PF_tabular | PF_graphical | Maps_&_aerials

PF tabular

PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1

Duration Average recurrence interval (years)

1 2 5 10 25 50 100 200 500 1000

5-min 0.421

(0.319-0.556) 0.488

(0.374-0.641) 0.600

(0.457-0.789) 0.691

(0.519-0.920) 0.814

(0.591-1.12) 0.906

(0.641-1.28) 0.997

(0.688-1.44) 1.09

(0.733-1.62) 1.22

(0.790-1.87) 1.31

(0.830-2.07)

10-min 0.675

(0.511-0.891) 0.783

(0.600-1.03) 0.963

(0.734-1.27) 1.11

(0.833-1.48) 1.31

(0.951-1.80) 1.46

(1.03-2.06) 1.60

(1.11-2.32) 1.75

(1.18-2.60) 1.94

(1.26-2.97) 2.07

(1.31-3.27)

15-min 0.839

(0.635-1.11) 0.971

(0.744-1.28) 1.19

(0.910-1.57) 1.37

(1.03-1.83) 1.61

(1.17-2.21) 1.80

(1.27-2.53) 1.97

(1.36-2.86) 2.16

(1.45-3.21) 2.40

(1.56-3.70) 2.59

(1.64-4.08)

30-min 1.16

(0.880-1.54) 1.34

(1.03-1.77) 1.65

(1.26-2.17) 1.89

(1.42-2.52) 2.22

(1.61-3.04) 2.47

(1.74-3.47) 2.71

(1.87-3.92) 2.97

(1.99-4.41) 3.31

(2.15-5.09) 3.58

(2.27-5.64)

60-min 1.51

(1.14-1.99) 1.75

(1.34-2.29) 2.15

(1.64-2.83) 2.47

(1.86-3.30) 2.91

(2.11-3.99) 3.24

(2.29-4.56) 3.57

(2.46-5.17) 3.92

(2.64-5.83) 4.40

(2.86-6.77) 4.78

(3.03-7.54)

2-hr 1.84

(1.41-2.41) 2.16

(1.66-2.80) 2.68

(2.06-3.49) 3.11

(2.35-4.10) 3.71

(2.71-5.03) 4.16

(2.96-5.80) 4.63

(3.21-6.63) 5.14

(3.47-7.55) 5.84

(3.81-8.88) 6.40

(4.07-9.96)

3-hr 2.04

(1.57-2.66) 2.41

(1.86-3.10) 3.01

(2.32-3.89) 3.51

(2.67-4.61) 4.22

(3.10-5.69) 4.76

(3.41-6.60) 5.34

(3.72-7.59) 5.95

(4.04-8.69) 6.82

(4.46-10.3) 7.50

(4.78-11.6)

6-hr 2.41

(1.87-3.11) 2.88

(2.23-3.64) 3.61

(2.80-4.62) 4.24

(3.24-5.50) 5.13

(3.80-6.85) 5.83

(4.20-8.00) 6.57

(4.60-9.24) 7.38

(5.03-10.6) 8.50

(5.59-12.7) 9.41

(6.02-14.4)

12-hr 2.84

(2.22-3.63) 3.40

(2.66-4.26) 4.27

(3.35-5.41) 5.02

(3.88-6.46) 6.08

(4.53-8.04) 6.92

(5.01-9.38) 7.80

(5.49-10.8) 8.76

(6.00-12.5) 10.1

(6.68-14.9) 11.2

(7.20-16.9)

24-hr 3.32

(2.61-4.20) 3.97

(3.14-4.94) 5.00

(3.95-6.27) 5.87

(4.57-7.48) 7.11

(5.34-9.29) 8.08

(5.89-10.8) 9.10

(6.45-12.5) 10.2

(7.04-14.4) 11.8

(7.83-17.2) 13.1

(8.44-19.4)

2-day 3.85

(3.05-4.82) 4.59

(3.66-5.66) 5.78

(4.60-7.18) 6.78

(5.32-8.55) 8.20

(6.20-10.6) 9.32

(6.84-12.4) 10.5

(7.48-14.3) 11.8

(8.16-16.4) 13.6

(9.07-19.5) 15.1

(9.77-22.1)

3-day 4.19

(3.34-5.21) 5.00

(4.00-6.12) 6.28

(5.03-7.76) 7.37

(5.81-9.24) 8.92

(6.78-11.5) 10.1

(7.47-13.4) 11.4

(8.18-15.4) 12.8

(8.92-17.7) 14.8

(9.92-21.1) 16.5

(10.7-23.9)

4-day 4.42

(3.53-5.47) 5.28

(4.24-6.43) 6.64

(5.34-8.17) 7.81

(6.18-9.74) 9.47

(7.22-12.1) 10.8

(7.97-14.1) 12.2

(8.73-16.3) 13.7

(9.54-18.8) 15.9

(10.6-22.5) 17.6

(11.5-25.5)

7-day 4.89

(3.94-6.01) 5.88

(4.74-7.08) 7.40

(5.99-9.02) 8.74

(6.96-10.8) 10.7

(8.17-13.5) 12.2

(9.06-15.8) 13.8

(9.98-18.4) 15.7

(10.9-21.3) 18.2

(12.3-25.6) 20.3

(13.3-29.1)

10-day 5.32

(4.30-6.50) 6.39

(5.17-7.66) 8.05

(6.54-9.76) 9.51

(7.60-11.7) 11.6

(8.94-14.6) 13.3

(9.91-17.2) 15.1

(10.9-19.9) 17.1

(12.0-23.1) 19.9

(13.4-27.8) 22.3

(14.6-31.6)

20-day 6.90

(5.63-8.34) 8.15

(6.69-9.73) 10.1

(8.32-12.2) 11.8

(9.54-14.4) 14.2

(11.0-17.7) 16.1

(12.0-20.5) 18.0

(13.1-23.5) 20.3

(14.3-27.1) 23.6

(16.0-32.4) 26.3

(17.3-36.8)

30-day 8.25

(6.76-9.91) 9.64

(7.98-11.5) 11.9

(9.82-14.2) 13.8

(11.2-16.7) 16.4

(12.7-20.2) 18.4

(13.8-23.2) 20.5

(15.0-26.5) 22.9

(16.2-30.3) 26.4

(17.9-36.0) 29.3

(19.3-40.8)

45-day 10.1

(8.34-12.1) 11.8

(9.79-13.9) 14.4

(12.0-17.2) 16.7

(13.6-20.0) 19.7

(15.4-24.3) 22.1

(16.7-27.8) 24.5

(18.0-31.5) 27.2

(19.3-35.7) 30.8

(21.0-41.7) 33.8

(22.3-46.6)

60-day 11.8

(9.75-14.0) 13.7

(11.4-16.1) 16.7

(13.9-19.8) 19.3

(15.8-23.1) 22.8

(17.9-28.0) 25.6

(19.4-32.0) 28.3

(20.8-36.2) 31.2

(22.2-40.7) 34.9

(23.8-46.8) 37.7

(24.9-51.7)

1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).

Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.

Please refer to NOAA Atlas 14 document for more information.

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PF graphical

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