WI_ERFO_(6)_Hydraulics.pdf

Memo mr u:\193804163\design\hydraulics\hyd_documentation_95%_110618\hyddoc_fr383_fr150_110618.docx

To: Lisa Landers From: Rob Monk FHWA – Eastern Federal Lands Division Stantec – St. Paul, MN File: 193804163 Date: November 6, 2018

Reference: WI ERFO FS 2016-1(6), Various Locations – Hydrologic Documentation

This memo provides the Hydrologic Documentation for eight (8) stream crossings and three (3) best management practices (BMPs) across multiple roadways, as detailed in the table below.

Stream Crossings BMPs Forest Road (FR) 150 1 3 Forest Road (FR) 383 7 0

Hydrology was completed using input from both the Federal Highway Administration (FHWA) and United States Forest Service (USFS). When applicable, WI regional regression analysis was used to determine peak flood flows. The rational method was used to determine peak flood flows for all smaller watersheds. Analysis was completed for the 2-, 10-, and 100-year recurrence intervals.

Forest Road 150

Based on the watershed areas not meeting minimum size requirements (≤0.31 mi2 actual vs. 0.66 mi2 required), the USGS regional regression equation (Area 4) could not be used for FR 150 culverts. Thus, based on conversations with FHWA and USFS, the Rational Method (Q=ciA) was used to determine peak flood flows. Rational method inputs for each culvert are shown in Table 1 below. Runoff coefficients (c) were determined using the WisDOT Facilities Design Manual for open space. The first listed c-value is used for smaller rain events (2- and 10-year) while the second c-value is used for larger events (100-year). NOAA Atlas 14 precipitation frequency data (inches/hour) was used to determine rainfall intensity (i) for each flood.

Watershed areas were delineated based on available County LiDAR at stream crossing and BMP locations called out during the joint-agency site visit (FHWA, USFS, Stantec – May 30th). An FR 150 Drainage Area Map is attached for review.

Table 1. FR 150 – Basin Characteristics & Flood Flows

BMPs Stream Basin Characteristic Units 7+00 10+75 15+00 150A

Area mi2 0.002 0.005 0.006 0.31

Area (A) ac 1.3 2.9 3.61 200.4 Runoff Coefficient (c) unitless 0.28/0.39 0.28/0.39 0.28/0.39 0.21/0.27

Time of Concentration (tc) minutes 8 11 15 94

Rainfall Intensity (i) (in/hr) 3.82 3.29 2.80 0.91 2-Year Flood Flow cfs 1.34 2.67 2.83 38.5

Rainfall Intensity (i) (in/hr) 5.64 4.87 4.15 1.38 10-Year Flood Flow cfs 1.97 3.95 4.19 58.0 Rainfall Intensity (i) (in/hr) 8.58 7.42 6.34 2.19

100-Year Flood Flow cfs 4.18 8.39 8.93 118.7

November 6, 2018 Lisa Landers

Reference: WI ERFO FS 2016-1(6), Various Locations – Hydrologic Documentation mr u:\193804163\design\hydraulics\hyd_documentation_95%_110618\hyddoc_fr383_fr150_110618.docx

Forest Road 383

Seven (7) stream crossings were analyzed to determine peak flows during the 2-, 10-, and 100-year floods. One stream crossing (Station 88+00) had a watershed area large enough to use the WI regional regression equation and will be examined separately. An FR 383 Drainage Area Map is attached for review.

Station 88+00 Crossing

Based on drainage basin characteristics, the USGS regional regression equation (WI, Area 4) was used to determine a peak 2-, 10-, and 100-year flood flow at Station 88+00 along FR 383. Basin characteristics used in the regression equation are shown in Table 2 below. The contributing watershed area was determined using a combination of available WI LiDAR data and USGS StreamStats, a web-based program used to determine watershed area and various watershed characteristics. Soil permeability of 56.06 in/hr (StreamStats) was lowered to 4.68 in/hr, the maximum allowable within the regression equation. A spreadsheet with basin characteristics and the regression equation computation is attached for review.

Table 2. FR 383 Sta. 88+00 – Basin Characteristics

Basin Characteristic Units Value

Drainage Area (A) Square Miles (mi2) 0.80 Storage (ST) Percent (%) 1.9

Main-Channel Slope (S) Feet/Mile (ft/mi) 163 Soil Permeability (SP) Inches/Hour (in/hr) 4.68

Mean Annual Snowfall (SN) Inches (in) 81.1 2-Year Flood Flow Cubic Feet per Second (cfs 45

10-Year Flood Flow Cubic Feet per Second (cfs) 106 100-Year Flood Flow Cubic Feet per Second (cfs) 124

Other Stream Crossings

Based on the watershed areas not meeting minimum size requirements (≤0.20 mi2 actual vs. 0.66 mi2 required), the USGS regional regression equation (Area 4) could not be used for FR 383 culverts. Thus, based on conversations with FHWA and USFS, the Rational Method (Q=ciA) was used to determine peak flood flows. Rational method inputs for each culvert are shown in Table 3 below. Runoff coefficients (c) were determined using the WisDOT Facilities Design Manual for open space. The first listed c-value is used for smaller rain events (2- and 10-year) while the second c-value is used for larger events (100-year). NOAA Atlas 14 precipitation frequency data (inches/hour) was used to determine rainfall intensity (i) for each flood.

Watershed areas were delineated based on available County LiDAR at stream crossing and BMP locations called out during the joint-agency site visit (FHWA, USFS, Stantec – May 30th).

November 6, 2018 Lisa Landers

Reference: WI ERFO FS 2016-1(6), Various Locations – Hydrologic Documentation mr u:\193804163\design\hydraulics\hyd_documentation_95%_110618\hyddoc_fr383_fr150_110618.docx

Table 3. FR 383 – Basin Characteristics & Flood Flows

Basin Characteristic Units 31+00 39+00 44+50 63+00 83+50 95+00

Area mi2 0.022 0.10 0.16 0.20 0.08 0.07

Area (A) ac 14.2 65.6 99.8 130.0 48.6 45.2 Runoff Coefficient (c) unitless 0.17/0.23 0.17/0.23 0.17/0.23 0.24/0.32 0.17/0.23 0.24/0.32

Time of Concentration (tc) minutes 24 53 68 47 49 24 Rainfall Intensity (i) (in/hr) 2.18 1.36 1.15 1.47 1.43 2.18 2-Year Flood Flow cfs 5.26 15.2 19.4 45.8 11.8 23.6

Rainfall Intensity (i) (in/hr) 3.25 2.06 1.72 2.21 2.16 3.25 10-Year Flood Flow cfs 7.85 22.9 29.3 69.0 17.8 35.3

Rainfall Intensity (i) (in/hr) 5.01 3.26 2.70 3.48 3.40 5.01 100-Year Flood Flow cfs 16.4 49.2 61.9 144.8 38.0 72.5

If you have any questions about the results of the Hydrologic Documentation please let me know using the contact information below.

Stantec Consulting Services Inc.

Rob Monk

Phone: (651) 604-4713 rob.monk@stantec.com

Attachment: FR 150 Drainage Area Map FR 383 Drainage Area Map Regression Spreadsheet (Sta. 88+00)

c. Michelle Garrigan, Stantec Rand Postell, Stantec

1742122

1742122

1745403

1745403

Revised: 2018-06-12 By: rmonk U:\193804163\GIS\Projects\Hydraulics_Working_rvm.mxd

Disclaimer: Stantec assumes no responsibility for data supplied inelectronic format. The recipient accepts full responsibility for verifying the accuracy and completeness of the data. The recipient releases Stantec, its officers, employees, consultants and agents, from any and all claims arising in any way from the content or provision of the data.

0 470 940 1,410 Feet

1:5,566 (At Original document size of 11x17)

Drainage Area Map

FR 150

1 inch = 463.81 feet

1722437

1722437

1725718

1725718

1728999

1728999

Revised: 2018-07-26 By: rmonk U:\193804163\GIS\Projects\Hydraulics_Working2_rvm.mxd

Disclaimer: Stantec assumes no responsibility for data supplied inelectronic format. The recipient accepts full responsibility for verifying the accuracy and completeness of the data. The recipient releases Stantec, its officers, employees, consultants and agents, from any and all claims arising in any way from the content or provision of the data.

0 750 1,500 2,250 Feet

1:9,026 (At Original document size of 11x17)

Drainage Area Map

FR 383

1 inch = 752.15 feet

31+00 39+00

44+50

63+00

88+00

83+50

95+00

WI ERFO FS 2016-1(6), FR383, 88+00

Regional Regression Equation (WI, Area 4) Proj. No. 193804163 6/12/2018

A 0.80

ST 1.9

S 163

SP 4.68 Lowered to maximum allowable from 56.06 in/hr (USGS StreamStats)

SN 81.1

A A ST S SP SN

Q2 45 2.69 0.864 -0.296 0.279 -0.250 0.490 Q5 74 6.76 0.858 -0.286 0.303 -0.259 0.370

Q10 100 9.74 0.856 -0.286 0.321 -0.255 0.332 Q25 137 13.7 0.856 -0.290 0.342 -0.246 0.299 Q50 167 16.6 0.857 -0.293 0.357 -0.238 0.281

Q100 201 19.4 0.857 -0.296 0.371 -0.229 0.269