DEWA Hydrology and Hydraulic Assessment Report Final_06-22-2020_compressed_no appendix_0004.pdf

Watergate Wetlands Restoration Project

Hydrologic and Hydraulic Assessment Report

FINAL

620/167491

Delaware Water Gap National Recreation Area — 294871 June 2020

As the nation’s principal conservation agency, the Department of the Interior has the responsibility for most of our nationally owned public lands and natural resources. This includes fostering sound use of our land and water resources;

protecting our fish, wildlife, and biological diversity; preserving the environment and cultural values of our national parks and historical places; and providing for the enjoyment of life through outdoor recreation. The department assesses our energy and mineral resources and works to ensure that their development is in the best interests of all our people by encouraging stewardship and citizen participation in their care. The department also has a major responsibility for American Indian reservation communities and for people who live in island territories under U.S. administration.

NPS D – 620/167491 / PMIS 294871 / June 2020

Delaware Water Gap National Recreation Area Hydrologic and Hydraulic Assessment Report FINAL i

TABLE OF CONTENTS

EXECUTIVE SUMMARY ................................................................................................ VII

INTRODUCTION

SITE MONITORING OBSERVATIONS

HISTORICAL HYDROLOGIC MONITORING EFFORTS

GROUNDWATER

SURFACE WATER

PERMANENT GAUGE STATIONS

TEMPERATURE

STREAM GEOMORPHOLOGY

SURFACE HYDROLOGY AND HYDRAULIC EVALUATION

MODELING PLATFORM

DRAINAGE AREA DELINEATION AND WATERSHED VARIABLES

Watershed Delineations Time of Concentration/Lag Time and Curve Number Determination

HEC-HMS

Model Calibration Model Results

CHANNEL HYDRAULIC MODELING

Existing Conditions Proposed Conditions Manning’s N Values Contraction and Expansion Coefficients Boundary Conditions Hydraulic Model Findings

GROUNDWATER MODELING AND WETLAND DESIGN

DESIGN CRITERIA

WETLAND GROUNDWATER MODEL

Water Mass Balance Precipitation Surface Water Inflow/Outflow Groundwater Inflow/Outflow Evapotranspiration Data Other Wetland Parameters

GROUNDWATER MODEL CALIBRATION

HABITAT DESIGN ELEVATIONS

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CLIMATE CHANGE EVALUATION

CLIMATE MODEL

Grid Location Future Precipitation Patterns Future Evapotranspiration

STORM EVENT DURATION DEPTH

WETLAND DESIGN EVALUATION FOR CLIMATE CHANGE

STREAM DESIGN EVALUATION FOR CLIMATE CHANGE

RENDERINGS AND POST CONSTRUCTION MONITORING

PROJECT GROUNDWATER AND DESIGN RENDERINGS

POST-CONSTRUCTION MONITORING

ACRONYMS AND ABBREVIATIONS

REFERENCES

LIST OF TABLES

Table 1. Sub-watershed Drainage Area Calculations

Table 2. Sub-watershed Time of Concentration, Lag Time and Curve Number Computations

Table 3. January 2018 Storm Event Recorded Peak Discharge and Runoff Volume by Gauge Point

Table 4. Calibrated Peak Discharge and Runoff Volume Comparison to Observed Data by Gauge Point

Table 5. HEC-HMS Runoff Output by Sub-watershed/Basin Model Junction

Table 6. Design Discharge Rates

Table 7. HEC-RAS Water Surface Elevations Comparison – 1-Year, 6-Hour Storm

Table 8. HEC-RAS 2-Year and 10-Year Velocity Comparison

Table 9. HEC-RAS 2-Year and 10-Year Shear Comparison

Table 10. Growing Season Dates Reported in WETS Table

Table 11. Aeroflex-Andover Airport Monthly Rainfall Summaries by Year

Table 12. Reference Curve Numbers

Table 13. Other Wetland Parameters

Table 14. Groundwater Analysis Calibrated Values for Well 1 – Parcel 4

Table 15. Groundwater Analysis Calibrated Values for Well 3 – Parcel 5

Table 16. Groundwater Analysis Calibrated Values for Well 4 – Parcel 3

Table 17. Groundwater Analysis Calibrated Values for Well 6 – Parcel 3

Table 18. Groundwater Analysis Calibrated Values for Well 7 – Parcel 3

Table 19. Groundwater Analysis Calibrated Values for Well 11 – Parcel 2 iii

Table 20. Groundwater Analysis Calibrated Values for Well 13 – Parcel 6

Table 21. Groundwater Analysis Calibrated Values for Well 14 – Parcel 1

Table 22. Groundwater Analysis Calibrated Values for Well 18 – Parcel 7

Table 23. Groundwater Analysis Calibrated Values for Well 19 – Parcel 7

Table 24. Saturation and Flooding Level by Habitat Type During The Growing Season (April 22 To October 18) For The Simulated Normal Year (2010)

Table 25. Climate Models Evaluated in Analysis

Table 26. Percent Change in Monthly Precipitation in 2080–2099 Relative to 1984–2003

Table 27. Percent Change in Monthly Precipitation by 2100 – Comparison of Modeled Analysis to Reference Study

Table 28. Identification of Climate Simulations of Interest for Each of the Observed Years Used in the Hydrologic Analysis

Table 29. Climate Simulations that Represent the Drier, Wetter, and Normal Future Years

Table 30. Future Change in Average Daily PET for Each Month for 2080–2099 Relative to 2084–2003

Table 31. Climate Simulations that Represent the Drier, Wetter, and Normal Future Years

Table 32. Climate Simulations that Represent the 10th, 50th, and 90th Percentiles for PET and Monthly Precipitation from April through November

Table 33. Projected Change in Return Periods for 2099

Table 34. Saturation and Flooding Level by Habitat Type During the Growing Season (April 22 To October

18) for the Simulated Future Condition Normal Year (2099)

Table 35. USACE Wetland Criteria Met by Habitat Type During the Growing Season (April 22 To October

18) for the Simulated Future Condition Normal, Wet, and Dry Year (2099)

Table 36. Water Surface Elevation Comparisons for 1- and 2-Year Storm Events

Table 37. Water Surface Elevation Comparisons for 10- and 25-Year Storm Events

Table 38. Water Surface Elevation Comparisons for 50- and 100-Year Storm Events

Table 39. Water Surface Elevation Comparisons for Flood Hazard Storm Event

LIST OF FIGURES

Figure 1. Project Area

Figure 2. Monitoring Wells

Figure 3. Sub-watersheds

Figure 4. Groundwater Model Parcels

Figure 5. Post-Construction Monitoring Wells iv

LIST OF CHARTS

Chart 1. Sample Groundwater Observations in Project Area

Chart 2. Groundwater to Surface Water Temperature Comparison from Pond 2

Chart 3. Groundwater to Surface Water Temperature Comparison from Pond 10

Chart 4. Millbrook Flatbrook Road Bridge Stream Gauge Discharge – January 2018 Storm Event

Chart 5. Brink Road Bridge Stream Gauge Discharge – January 2018 Storm Event

Chart 6. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 1 – Parcel 4

Chart 7. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 3 – Parcel 5

Chart 8. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 4 – Parcel 3

Chart 9. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 6 – Parcel 3

Chart 10. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 7 – Parcel 3

Chart 11. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 11 – Parcel 2

Chart 12. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 13 – Parcel 6

Chart 13. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 14 – Parcel 1

Chart 14. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 18 – Parcel 7

Chart 15. Groundwater Analysis Calibrated Modeled to Observed Comparison for Well 19 – Parcel 7

Chart 16. Well 1 – Parcel 4 Groundwater Model (Wet, Normal, and Dry Year)

Chart 17. Well 3 – Parcel 5 Groundwater Model (Wet, Normal, and Dry Year)

Chart 18. Well 4 – Parcel 3 Groundwater Model (Wet, Normal, and Dry Year)

Chart 19. Well 6 – Parcel 3 Groundwater Model (Wet, Normal, and Dry Year)

Chart 20. Well 7 – Parcel 3 Groundwater Model (Wet, Normal, and Dry Year)

Chart 21. Well 11 – Parcel 2 Groundwater Model (Wet, Normal, and Dry Year)

Chart 22. Well 13 – Parcel 6 Groundwater Model (Wet, Normal, and Dry Year)

Chart 23. Well 14 – Parcel 1 Groundwater Model (Wet, Normal, and Dry Year)

Chart 24. Well 18 – Parcel 7 Groundwater Model (Wet, Normal, and Dry Year)

Chart 25. Well 19 – Parcel 7 Groundwater Model (Wet, Normal, and Dry Year)

Chart 26. Equivalent Carbon Dioxide Concentrations in the Atmosphere under a Series of Emissions Scenarios

Chart 27. Ensemble Average Across the Collection of the Climate Simulations

Chart 28. Projected Precipitation for the Climate Simulations Identified to Represent 10-Percentile/Dry Observed Year, 50-Percentile/Normal Observed Year, and 90-Percentile/Wet Year

Chart 29. Projected Precipitation for the Climate Simulations Identified to Represent 10th Percentile/Dry Observed Year, 50th Percentile/normal Observed Year, and 90th Percentile/wet Year

Chart 30. Well 1 – Parcel 4 Groundwater Model (Wet, Normal, and Dry Year - 2099)

Chart 31. Well 3 – Parcel 5 Groundwater Model (Wet, Normal, and Dry Year - 2099)

Chart 32. Well 4 – Parcel 3 Groundwater Model (Wet, Normal, and Dry Year - 2099) v

Chart 33. Well 6 – Parcel 3 Groundwater Model (Wet, Normal, and Dry Year - 2099)

Chart 34. Well 7 – Parcel 3 Groundwater Model (Wet, Normal, and Dry Year - 2099)

Chart 35. Well 11 – Parcel 2 Groundwater Model (Wet, Normal, and Dry Year - 2099)

Chart 36. Well 13 – Parcel 6 Groundwater Model (Wet, Normal, and Dry Year - 2099)

Chart 37. Well 14 – Parcel 1 Groundwater Model (Wet, Normal, and Dry Year - 2099)

Chart 38. Well 18 – Parcel 7 Groundwater Model (Wet, Normal, and Dry Year - 2099)

Chart 39. Well 19 – Parcel 7 Groundwater Model (Wet, Normal, and Dry Year - 2099)

LIST OF IMAGES

Image 1. Grid Cell Used to Estimate Future Change in Daily Precipitation and Evapotranspiration

APPENDIXES

Appendix A—Stage-Discharge Charts

Appendix B—Project Photos

Appendix C—Project Area Geomorphology Data

Appendix D—Time of Concentration, Lag Time, and Curve Number Computations

Appendix E—HEC-HMS Watershed Model

Appendix F—Hydraulic Model

Appendix G—Channel Structure Design Calculations

Appendix H—Groundwater Model Parcel Curve Number Calculations

Appendix I—Project Groundwater/Design Comparison Renderings vi

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EXECUTIVE SUMMARY

The National Park Service (NPS) Denver Service Center, in coordination with the NPS Delaware Water Gap National Recreation Area (DEWA) park staff and Region 1 Regional Office, proposes to restore wetlands associated with Van Campens Brook at the Watergate Recreation Site by removing artificial dams and human-made ponds, and reestablishing the connection between Van Campens Brook and its floodplain. WSP USA, Inc. (WSP) was hired to perform predesign, schematic design, design development, construction documents, and supplemental services for the NPS DEWA Watergate Wetlands Restoration Project (project) in support of the development of 33-credit acres of wetland mitigation through reestablishment of palustrine wetland habitat and hydraulic restoration of Van Campens Brook. The project will result in a more natural and high-functioning wetland and riparian floodplain system, improved floodplain connectivity within the project area, and more natural fluvial dynamics within Van Campens Brook.

WSP conducted geomorphic surveys, surface and sub-surface hydrologic monitoring (including water temperature monitoring), hydrologic and hydraulic modeling, and climate adaptation analysis in support of the wetland restoration design. The hydrologic monitoring and hydraulic modeling were performed in consideration of the National Park Service Procedural Manual #77-1: Wetland Protection (NPS 2012a) and the Final Statement of Findings (NPS 2012b), which guided the development and success criteria for this project. Hydrologic and hydraulic models were developed to evaluate the relationship of surface water and groundwater with the wetland restoration design.

Surface water modeling was performed through a three-part modeling platform: the hydrologic model Soil Water Assessment Tool (SWAT) (Arnold et al. 1998, 2012), used through the ESRI ArcGIS program interface (ArcSWAT); the US Army Corps of Engineers (USACE) Hydrologic Engineering Center (HEC)-Hydrologic Modeling System (HMS); and the HEC-River Analysis System (RAS) hydraulic model. The ArcSWAT model was used to delineate watershed limits and flow paths. The HEC-HMS system evaluated surface water volumes and peak discharges for the project using the model results from the ArcSWAT and methods outlines by the US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) (USDA-NRCS 1986 and 2010). The one-dimensional model HEC-RAS was used to analyze river flow, including velocity and shear analyses.

Watershed modeling was calibrated using observed surface water data collected by NPS. Data collected from the permanent gauge stations was used to transform the observed water surface data into a discharge observation for a January 2018 storm event, which was routed through the HEC- HMS model. Model parameters were modified to mimic the upstream and downstream project limits volume of runoff and peak discharge to the extent feasible with the data collected. Results of the HEC-HMS model were routed through the HEC-RAS platform to simulate water surface elevations, velocities and shear stresses for a range of storm events to guide the design of bank and channel restoration of Van Campens Brook.

A groundwater modeling analysis was performed for the proposed wetland restoration of the project floodplain to predict groundwater elevation variability during the growing season for a representative normal, wet, and dry year of precipitation to set design elevations for functional palustrine wetland habitats. Design habitats proposed include palustrine emergent, scrub-shrub, and forested wetlands as observed at the reference site and detailed in the Wetlands Reference Site and Stream Reference Reach Report. The focus of the groundwater elevation analysis was to evaluate the site groundwater fluctuation and determine grading elevations to meet the two wetland saturation criteria set by USACE.

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The groundwater model was developed following the Regionalized Water Budget Manual for Compensatory Wetland Mitigation Sites in New Jersey (DEP 2008). The project was compartmentalized into multiple parcels based on flow paths and watershed areas considering the conceptual wetland design, which was then calibrated at specific groundwater monitoring wells within each parcel. Each monitoring well was calibrated using the water mass balance equation (DEP 2008) and data collected from 2016. Following calibration of each well, rainfall and evapotranspiration data for the representative normal, wet, and dry year precipitation were analyzed within the model. As the project is considered a groundwater slope-controlled type wetland (DEP 2008) based on the observed groundwater observations, gradients between the monitoring well points were utilized to set design elevations for the targeted wetland habitats.

Temperature recordings were utilized to assess potential thermal water transfer from the existing large open ponds (Pond 2 and Pond 10) to Van Campens Brook via groundwater exchange. The analysis determined that the primary source of thermal warming of Van Campens Brook is due to solar radiation on the stream and adjacent open lawn areas rather than groundwater exchange via the large ponds.

The climate change evaluation effort applied statistically reduced regional estimates for daily precipitation and temperature data to estimate the local future change in daily precipitation and evapotranspiration for the project area. Although NPS produced a DEWA region-specific climate adaptation study (Gonzalez 2016), the analysis performed provided only monthly average calculations for precipitation and temperature projections, which was not enough to incorporate into the daily groundwater elevation model simulations to evaluate climate adaptation for the proposed project. To achieve the detail needed for the analysis, the World Climate Research Programme’s Coupled Model Intercomparison Project phase 5 (CMIP5) Localized Constructed Analogs (LOCA) data was utilized, which are statistically downscaled data of the daily temperature and precipitation data of coarser global climate models (GCMs). The representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios were evaluated for the potential precipitation and temperature change for the year 2099. The results of the models were concluded into a potential dry year (10th percentile of the modeled climate scenarios), normal year (50th percentile of the modeled climate scenarios) and wet year (90th percentile of the modeled climate scenarios) using the chi-squared method for both precipitation and evapotranspiration data. Additionally, using the statistically downscaled CMIP5 precipitation data, the annual maximum for each year for each climate simulation (1980–2099) was identified and ranked to determine the future storm event for 2099. Utilizing the predicted 2099 storm event and current conditions storm event, a percent change was evaluated for the rainfall events under the dry, normal, and wet year climate models selected.

The normal year predicted storm event precipitation depth was routed through HEC-HMS to determine future discharge rates for each storm event. The predicted precipitation and evapotranspiration were evaluated within the groundwater modeling analyses. The future peak discharges also were routed through the HEC-RAS model to assess potential impacts due to climate change.

Based on these analyses, the proposed design addresses the potential increase in saturation and flooding from future climate change while still meeting design criteria for wetlands and stream functions under current conditions. In addition, a post-construction monitoring plan for proposed groundwater wells within the restored wetlands was developed to continue monitoring of hydrology in accordance with the Regionalized Water Budget Manual for Compensatory Wetland Mitigation Sites in New Jersey (DEP 2008).

INTRODUCTION

The National Park Service (NPS) Denver Service Center, in coordination with the NPS Delaware Water Gap National Recreation Area (DEWA) park staff and Region 1 Regional Office, proposes to restore wetlands associated with Van Campens Brook at the Watergate Recreation Site by removing artificial dams and human-made ponds, and reestablishing the connection between Van Campens Brook and its floodplain. These restoration efforts are being conducted as part of a larger compensatory mitigation effort for unavoidable impacts on wetlands associated with the Susquehanna to Roseland 500-kilovolt Transmission Line Project.

WSP USA, Inc. (WSP) was hired to perform predesign, schematic design, design development, construction documents, and supplemental services for the NPS DEWA Watergate Wetlands Restoration Project (project) (figure 1). The principal project goal is to generate 33-credit acres of wetland mitigation through reestablishment of palustrine wetland habitat and hydraulic restoration of Van Campens Brook. The project will result in a more natural high-functioning wetland and riparian floodplain system, improved floodplain connectivity in the project area, and more natural fluvial dynamics within Van Campens Brook.

The approximately 114-acre project area is located in Hardwick Township in Warren County, New Jersey. The project area includes a segment of Van Campens Brook and its associated floodplain, a New Jersey Department of Environmental Protection (DEP) Category 1 waterway and designated trout production stream, whose contributing watershed is contained solely within NPS property.

Historical modifications, including land clearing, grading, and damming of the brook to create a series of ponds, historical farming fields, and homestead sites (now recreational trails and picnic areas), substantially degraded on-site habitat, which was further impaired by non-native invasive vegetation throughout the project area.

This report summarizes the findings from the hydrologic monitoring, the hydraulic modeling observations, and the design implemented for the project. The hydrologic monitoring and hydraulic modeling were performed in consideration of the National Park Service Procedural Manual #77-1:

Wetland Protection (NPS 2012a) and the Final Statement of Findings (NPS 2012b), which guided the development and success criteria for this project.

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Project Area

Stream

Sources:

ESRI Basemap Imagery;

NJDEP Landuse Landcover, 2015;

USFWS, NWI Wetlands, 2019.

Pike Sussex

Monroe

Fi Pro gure 1 ject Area

NPS DEWA-294871

Watergate Wetland Restoration

Warren Coordinate System:

New Jersey State Plane North American Datum 1983

0 400 800 Feet ERTYMay 2020

SITE MONITORING OBSERVATIONS

HISTORICAL HYDROLOGIC MONITORING EFFORTS

NPS has been monitoring hydrology in the project area since December 2015 after installing 30 groundwater wells and 11 stream water surface gauges. All gauges were piezometer pressure reading transducers capable of recording temperature and water level pressure at the gauge. Additionally, a barometric piezometer was installed for site-specific compensation of water level pressure to record depths of water at the gauge.

From late 2019 into early 2020, WSP installed an additional eight groundwater wells (including reinstalling three groundwater wells observed to be broken at the beginning of work), replaced five stream surface water gauges, and installed two permanent flow monitoring gauge stations (located at the Millbrook Flatbrook Road bridge and Brink Road bridge) and two pond water surface gauges at the project. In addition, five groundwater wells were installed at the project reference site, as discussed within the Wetlands Reference Site and Stream Reference Reach Report. Gauges were installed on-site to observe temperature, groundwater and surface water fluctuations over time.

Data provided by NPS from December 2015 to January 2017, as well as data downloaded from the wells and additional gauges installed, provided semi-continuous groundwater and surface water monitoring for the project area from December 2015 to April 2020 (the extent of data collected and used within these analyses).

GROUNDWATER

Groundwater wells were installed by WSP following the Technical Standard for Water-table Monitoring of Potential Wetland Sites (USACE 2005), Guideline for Conducting, Reporting Hydrologic Assessments of Potential Wetland Sites (USACE 2000), and Installing Monitoring Wells in Soils (Version 1.0) (Sprecher 2008) protocols. To date, 31 2-inch PVC shallow monitoring wells remain installed and functioning throughout the project area (figure 2). This includes three broken wells and five new wells installed by WSP with four wells broken and not replaced. A small sample of the general groundwater well observations (12 wells within the areas of proposed wetland creation), by elevation, from September 2019 to December 2019 are shown in chart 1 to show the general difference in elevations observed through the project area. Ground and well casing elevations were provided by Dykstra Associates, a licensed New Jersey surveyor contracted for the survey of this project. These surveyed elevations were used to convert water depth readings from the wells to elevations in feet North American Vertical Datum of 1988 (feet NAVD88). All elevations in this report are in feet NAVD88.

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Figure 2 Monitoring Wells

Sources: ESRI Basemap Imagery;

WSP, 2020. Monroe

Sussex

Warren

Pike

May 2020

Coordinate System:

New Jersey State Plane

North American Datum 1983 0 200 400

Feet

NPS DEWA-294871

Watergate Wetland Restoration

Project Area

Monitoring Well

Stream Gauge

ERTY

Reference period of observed groundwater observations through the project area from September to December 2019.

CHART 1. SAMPLE GROUNDWATER OBSERVATIONS IN PROJECT AREA

The groundwater observations, by well, indicate a general difference in the overall elevations of groundwater throughout the project area but little variability between monitoring wells in terms of the change in groundwater elevations due to rainfall. The project area is considered as a groundwater slope-controlled wetland (DEP 2008) for construction in the Valley and Ridge Physiographic Province of New Jersey based on the differences in elevations observed throughout the project. As such, average groundwater elevations and gradients between the wells were considered in the analysis and design for wetlands, discussed below.

SURFACE WATER

WSP removed all 11 surface water gauges installed during the 2015 to 2017 monitoring work because they were non-functioning or were not reporting viable data for design and repurposed the gauges as additional groundwater wells. WSP also installed wells at 5 stream surface monitoring locations and 2 pond monitoring locations. The surface water gauges were stationed along Van Campens Brook in deep pools (figure 2). The gauges were connected to concrete blocks using a metal plate with anchors that were screwed into the concrete block. The concrete blocks were anchored into the Van Campens Brook stream bed to avoid dislodging and transport of the block during large storm events.

The pond monitoring locations (one each in Pond 10 and Pond 2, figure 2) were installed via rebar inserted into the pond bank. Dykstra Associates collected elevations for the top of the rebar and top of the metal plate on the stream monitoring gauges for depth to elevation compensations.

PERMANENT GAUGE STATIONS

Two permanent flow monitoring gauge stations were installed at the Millbrook Flatbrook Road bridge (upstream project limits) and the Brink Road bridge (downstream project limits). Each gauge station was constructed of an Onset HOBO U30 USB weather station data logger and Stevens SDX submersible depth transmitter and solar panel. These loggers can record up to 5-feet of water and require periodic downloading to acquire the recorded water depth data. Remote telemetry was not used for the project because of the poor cellular service within the valley of the project. Additionally, a stage ruler was installed adjacent to the depth transmitter in the brook and a rain gauge was installed at the Millbrook Flatbrook Road.

Stage-discharge charts (appendix A) were developed for each gauge station by collecting channel velocity recordings and channel topography at each gauge station. Dykstra Associates, with WSP personnel oversight, collected geomorphic-specific cross-sections, including top of bank elevations, channel toe, thalweg and other floodplain characteristics to develop cross-sectional area at various depths. Stage rulers and depth transmitters were surveyed for elevations to correlate depths observed on the stage ruler to the recorded depth of water above the sensor and corresponding cross-sectional area by stage. Velocity measurements were collected using an FH950 Portable Velocity Meter at 1-foot increments along areas of flow at each surveyed cross-section, which were compounded into an average channel velocity measurement for the flow observed. Two velocity recording events were performed, one during a normal baseflow condition on January 23, 2020, and another on January 29, 2020, following a storm event in which water levels had increased but were still traversable by foot.

Depth observations and area calculations for the two velocity recording measurement events were used to calibrate Manning’s velocity equation (equation 1) at each gauge station to approximate average velocities based on the observed stage. Equation variables include Manning’s roughness coefficient, calibrated based on area and velocity measurements; the hydraulic radius of the channel flow determined by the stage depth and cross-sectional area; and the channel slope determined by the top of bank slope between upstream and gauge station cross sections surveyed by Dykstra Associates.

Equation 1:

𝑉𝑉 =

1.49 𝑛𝑛

𝑅𝑅2/3𝑆𝑆1/2

where

𝑉𝑉 = 𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣 (𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓/𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠)

𝑛𝑛 = 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚’𝑠𝑠 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟ℎ𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐

𝑅𝑅 = ℎ𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 (𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓)

𝑆𝑆 = 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 (𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓/𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓)

Assumptions were applied in the development of the stage-discharge charts, such as using a consistent slope collected from the top of the bank delineation in the Manning’s equation, whereas the water surface slope is likely to be subtly variable based on flow events.

TEMPERATURE

Two transects of gauges were installed to identify potential contributions of surface water temperatures from Pond 2 and Pond 10 to Van Campens Brook. Each gauge installed at the project measures the water temperature simultaneously with every pressure reading logged. The temperature readings recorded during November 2019 through April 2020 are provided in charts 2 and 3. The gauge locations are shown on figure 2.

Temperature data recorded between November 2019 to April 2020 using surface water gauges and groundwater gauges placed in a transect at Pond 2 to Van Campens Brook to correlate possible thermal temperature pollution into Van Campens Brook.

CHART 2. GROUNDWATER TO SURFACE WATER TEMPERATURE COMPARISON FROM POND 2

Temperature data recoded between November 2019 to April 2020 using surface water gauges and groundwater gauges placed in a transect at Pond 10 to Van Campens Brook to correlate possible thermal temperature pollution into Van Campens Brook.

CHART 3. GROUNDWATER TO SURFACE WATER TEMPERATURE COMPARISON FROM POND 10

The temperature comparison observations from the transect along Pond 10 provide the most direct observation of the potential, or lack thereof, thermal exchange between the larger pond waters and the shallow groundwater flows into Van Campens Brook. Monitoring wells 33 and 34 are located in the maintained open grass field (figure 2) with average groundwater elevations observed at 2.3 and

1.2 feet below ground surface, respectively. These wells recorded rapidly fluctuating temperatures (a short duration increase or decrease over two to three days that is not in line with the general trend of temperature change), similar to the wells located in the open surface water (Pond 01 and Stream 01), but to a lesser extreme. Monitoring well 35, located adjacent to Van Campens Brook within tree canopy coverage and south of monitoring well 34, recoded limited variability in temperature changes with an average depth of water of 3.3 feet below ground surface. This indicates that, while the open ponds may have a short range of influence in increasing adjacent groundwater temperatures (observed higher temperatures of monitoring well 33 in November following the summer months), the stronger influence on temperature variability is likely caused by solar radiation along areas devoid of canopy coverage in shallower depths below ground surface. This is supported by the observations in the second transect installed along Pond 2 and by the surface water monitoring data from Van Campens Brook collected by NPS (NPS 2020, pers. comm., P. Sharpe).

Both monitoring wells 36 and 37 adjacent to Pond 2 were installed in locations with tree canopy coverage and shading with average groundwater depths at 1.6 and 2.5 feet below ground surface, respectively. While the recorded temperatures indicate some variations, as expected during normal daily temperature changes on shallow groundwater wells, it is limited in increasing temperatures as observed in the open water Pond 2 gauge. These observations, although analyzed during the winter and not during the high temperatures in the summer, corroborate the long-term stream temperature monitoring of Van Campens Brook and the conclusions provided by the draft Thermal Regime of Van Campens Brook – June, 2018 through October, 2019 developed by NPS (Tzilkowski 2019).

Pond 10 does, however, pose some potential thermal warming influence on Van Campens Brook because of its proximity/location to the brook. If there is a shallow cone of influence of thermal leaching from the ponds around its perimeter, this would directly leach into Van Campens Brook at the southern limits of the project area because the stream is located at the toe of the Pond 10 embankment. Temperature monitoring will continue through the year during which additional comparisons can be made using summer temperatures. At this time, based on the data collected and long-term stream temperature monitoring of Van Campens Brook, it is anticipated that the extreme change of temperature increase along the southern limits of Van Campens Brook in the project area is due to solar radiation of the stream and lack of proper canopy coverage.

STREAM GEOMORPHOLOGY

The stream geomorphology assessment, completed on January 6 and 7, 2020, evaluated the project reach and the reference reach of Van Campens Brook. The reference reach data and discussion can be found in the Wetlands Reference Site and Stream Reference Reach Report (WSP 2020) but included approximately 230 feet of longitudinal profile survey and a low-energy cross section survey. The assessment of the project area included approximately 3,350 feet of geomorphic observations which included identifying bedrock locations in the channel, mass wasting of the channel banks, and other geomorphological significant features of Van Campens Brook. Photos of the observations are included in appendix B of this report. Longitudinal profiles and cross section surveys of the recorded reach were not collected due to its rate of manipulation. The upper portions of the project area, upstream of the geomorphology assessed area, contained mostly functioning substrate profiles with only moderate entrenchment. Historical observations of Van Campens Brook have been of an actively evolving channel based on high sediment loads and natural influences in this forested section along a segment of wider valley between two high ridges. Van Campens Brook is classified as a C3 channel type system (Rosgen 1996) within the project area.

Six Wolman pebble counts (Wolman 1954, modified by Rosgen 1996) were conducted along the southern limits of the project in Van Campens Brook, including four riffle pebble counts and two bar pebble counts (appendix C). The channel slope varies through the project area. Moderate slope observations (0.013 feet/feet to 0.015 feet/feet) were observed within stable portions of the brook to the north, followed by a steeper slope (0.018 feet/feet) along the area of failed check dams to the southeast of the project area, with a drastic decrease in slope (0.004 feet/feet) at the southwestern end of Pond 10. The variability in slope and manipulation of the channel profile (dams and historical relocation for agricultural and recreational use) has destabilized the lower portions of the brook, leading to high banks and entrenchment with mass wasting into the channel. The manipulation has also led to braiding of the channel profile in the entrenched lower portions of manipulated channel alignment. Additionally, the sudden change of shallow slope and presence of bedrock has caused an over widening of the channel, reduced velocities, and settlement of fine sediments in the portions of Van Campens Brook below Pond 10.

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SURFACE HYDROLOGY AND HYDRAULIC EVALUATION

MODELING PLATFORM

The modeling framework for the surface hydrology and hydraulic evaluation of the project consisted of the following:

A watershed model that provided inputs of watershed area and longest flow path for incorporation into the watershed routing model: The hydrologic model Soil Water Assessment Tool (SWAT) (Arnold et al. 1998, 2012), used through the ESRI ArcGIS program interface (ArcSWAT), was selected to perform the simulation. SWAT is a continuous-time simulation, semi-distributed, quasi-process-based watershed model.

A basin hydrologic watershed model to determine boundary flows for various storm events to route into the in-stream model: The US Army Corps of Engineers (USACE) Hydrologic Engineering Center (HEC)-Hydrologic Modeling System (HMS) was used for this component of the modeling. The HEC-HMS is a physically based modeling system designed to simulate precipitation-runoff characteristics based on many watershed details (USACE 2016).

An in-stream hydraulic routing analysis model: The HEC-River Analysis System (RAS) hydraulic model was used for this component of the modeling framework. The one-dimensional model HEC-RAS is a physically based modeling system to analyze river flow, sediment, and water quality dynamics. HEC-RAS was selected because it has been present in the public realm for more than 15 years and has been peer reviewed (USACE 2010a, b). It is also widely used by many government agencies and private firms.

The ArcSWAT model, HEC-HMS, and HEC-RAS were externally coupled such that the results of the ArcSWAT model and HEC-HMS were used as an input to the HEC-RAS model without changing the codes of the models.

DRAINAGE AREA DELINEATION AND WATERSHED VARIABLES

Watershed Delineations

ArcSWAT 2012 was used to determine watershed drainage areas and longest flow paths for time of concentration analyses to incorporate into the HEC-HMS modeling platform. As mentioned above, SWAT is a continuous-time simulation, semi-distributed, quasi-process-based watershed model. The US Geological Survey (USGS) digital elevation model (DEM), published in 2015 for the project area, was used within the modeling platform. Sub-watershed areas were incorporated along upper portions of the Van Campens Brook to avoid having a sub-watershed area greater than 5 square miles. Results of the watershed delineations were cross-checked with watershed outputs provided by the USGS StreamStats online software. Delineated watersheds are shown in figure 3. The resulting drainage areas by sub-watershed are provided in table 1.

H H

H

M i l br o ok R d

H H

HH

SB160

SB190

SB220

O ld M in e R d

H H e n s

J Lak e c am p k a v ko la Va m Bro o

SB200

SB180

SB230 SB210

SB100

SB110

SB120

SB120

SB110H

SB140 SB130

SB150

H

SB170

H

HH H

H Project Area

Sub-watershed

Longest Flow PathH

Sources: ESRI Basemap Imagery;

WSP, 2020.

Pike

Monroe Sussex

Warren

Fi Sub-wa gure 3 tersheds

NPS DEWA-294871

Watergate Wetland Restoration

Coordinate System:

New Jersey State Plane

North American Datum 1983 0 0.25 0.5

Miles ERTYMay 2020

TABLE 1. SUB-WATERSHED DRAINAGE AREA CALCULATIONS

Sub-watershed Name Drainage Area (Acres)

SB100 480.90

SB110 766.10

SB120 218.40

SB130 502.90

SB140 258.70

SB150 516.30

SB160 241.00

SB170 185.60

SB180 186.70

SB190 121.60

SB200 172.80

SB210 126.70

SB220 192.00

SB230 128.00

Time of Concentration/Lag Time and Curve Number Determination

Time of concentration and lag time were determined for each sub-watershed using the watershed lag method (USDA-NRCS 2010). Weighted curve number (CN) determinations for each sub-watershed were evaluated using the Urban Hydrology for Small Watersheds (TR-55) procedures (USDA-NRCS 1986). Land uses for the watershed were obtained from DEP's Geographic Information Systems (GIS) database and soils information was obtained from the US Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS) web soil survey. All initial values determined through these analyses were subsequently calibrated through the HEC-HMS model. Computations are included in appendix D. Table 2 provides the initial values calculated by sub-watershed.

TABLE 2. SUB-WATERSHED TIME OF CONCENTRATION, LAG TIME AND CURVE NUMBER COMPUTATIONS

Sub-watershed Name Time of Concentration

(Hour) Lag Time

(Hour) Curve Number

SB100 1.23 0.74 78

SB110 1.34 0.80 80

SB120 0.74 0.44 73

SB130 1.31 0.78 75

SB140 0.84 0.51 73

SB150 1.09 0.66 75

SB160 0.74 0.44 77

SB180 0.56 0.33 74

Sub-watershed Name Time of Concentration

(Hour) Lag Time

(Hour) Curve Number

SB170 0.58 0.35 78

SB190 0.50 0.30 73

SB200 0.23 0.14 73

SB210 0.58 0.35 73

SB220 0.66 0.40 78

SB230 0.77 0.46 72

HEC-HMS

HEC-HMS model version 4.3 was used to develop the direct runoff flow rates throughout the watershed for simulation in the HEC-RAS model. USACE designed the HEC-HMS model to simulate the precipitation-runoff processes of drainage basins. The primary components of the HEC-HMS used for this assessment were the basin model manager and the meteorologic model manager. The parameters obtained from the ArcSWAT model, in addition to lag time and initial sub-watershed characteristics, served as the modeling parameters for the HEC-HMS model. Storm event precipitation data for the project area was obtained from the National Oceanic and Atmospheric Administration (NOAA) Precipitation Frequency Data Server (NOAA 2020) and are provided as part of appendix E.

For simulation of the HEC-HMS models, the NRCS unit hydrograph method was selected using a Type III storm distribution for the State of New Jersey. Inputs to the basin model manager included the drainage area, CN, and lag time.

Model Calibration

The HEC-HMS model was calibrated using data collected from stream gauges installed by NPS in the 2015 to 2017 monitoring period at Millbrook Flatbrook Road bridge at the upstream limits of the project area and Brink Road bridge at the downstream limit of Van Campens Brook. Stage recordings from the precipitation event between January 10, 2018 and January 14, 2018 were interpolated into stream discharge using the stage-discharge relationships developed for the permanent gauge stations. Because the locations of these stream gauges were slightly different than the permanent gauge stations, a separate stage-discharge relationship curve (included in appendix A) was generated using cross-sectional data collected near the stream gauge. The same interpolated velocity values used in the permanent gauge station set up were used again. Charts 4 and 5 provide the time-discharge observations at the Millbrook Flatbrook Road and Bring Road bridge gauges, respectively.

CHART 4. MILLBROOK FLATBROOK ROAD BRIDGE STREAM GAUGE DISCHARGE – JANUARY 2018 STORM EVENT

CHART 5. BRINK ROAD BRIDGE STREAM GAUGE DISCHARGE – JANUARY 2018 STORM EVENT

The HEC-HMS model was established so that a junction within the basin model was included at the Millbrook Flatbrook Road bridge and the Brink Road bridge to calibrate input variables to match the peak discharges and runoff volumes observed during this storm event. Peak discharges and total runoff volume recorded at each bridge during the January 2018 storm event are provided in table 3.

TABLE 3. JANUARY 2018 STORM EVENT RECORDED PEAK DISCHARGE AND RUNOFF VOLUME BY GAUGE POINT

Gauge Station Peak Discharge

(Cubic Feet per Second) Runoff Volume

(Cubic Feet)

Millbrook Flatbrook Road Bridge 16.97 25.87

Brink Road Bridge 53.42 69.55

Recorded hourly rainfall data was simulated through the HEC-HMS model with input variables adjusted to meet the targeted peak discharge and runoff volume at each bridge junction in the basin model. Hourly rainfall from the Aeroflex-Andover Airport station (GHCND: USW00054779) located in the Andover Township was obtained from the Northeast Regional Climate Center at Cornell University. Aeroflex-Andover Airport is located approximately 20 miles east of the project area and has measured continuous precipitation and evapotranspiration data from 1999 to present day.

The goals of the model calibration were to adjust CNs and lag times so that peak discharges and runoff volumes matched the data recorded by the installed gauges. An adjustment factor was applied to all sub-watershed CN values and lag times until the total model runoff volume and peak discharges corresponded with the recorded measurements at the installed gauges both upstream and downstream of the site during the selected storm event.

Following calibration, modeled peak discharges closely corresponded to recorded peak discharges at the Millbrook Flatbrook Road bridge, and modeled runoff volume closely corresponded to recorded runoff volume at the Brink Road bridge. However, the modeled versus recorded runoff volume at the Millbrook Flatbrook Road bridge and modeled versus recorded peak discharge at the Brink Road bridge did not closely correspond.

This is attributed to the in-proper installation of previous stream gauges by others used for the calibration process. The runoff volume calculated at Millbrook Flatbrook Road bridge did not fully capture the storm event based on the gauge recording of the January 2018 event because the gauge was installed above the channel bottom. This would have missed a portion of baseflow and rising waters that are missing towards the overall volume of runoff calculation. Additionally, both the Millbrook Flatbrook Road and Brink Road bridge stream gauges were installed underneath of the structures rather than upstream or downstream of the structures. This alters the cross-sectional area of open flow which impacts the calculated discharges and velocities measured in the field.

Ultimately, CNs were decreased by 4% for all sub-watersheds upstream of the Millbrook Flatbrook Road bridge. Sub-watersheds downstream of Millbrook Flatbrook road were increased by 18%. Lag times were adjusted at the same rate as the CNs. The calibrated peak discharge and runoff volumes compared to the observed data are presented in table 4. This was the best calibration possible with the data available. For the application of the model and design, WSP is confident with the use of the results. More accurate calibration would be possible for future studies utilizing the ongoing rainfall and discharge measurements made directly at the site through the recently installed permanent gauge stations.

TABLE 4. CALIBRATED PEAK DISCHARGE AND RUNOFF VOLUME COMPARISON TO OBSERVED DATA BY GAUGE POINT

Gauge Station

Modeled Peak

Discharge (Cubic Feet per Second)

Observed Peak

Discharge (Cubic Feet per Second)

Percent Difference

Modeled Runoff Volume (Cubic Feet)

Observed Runoff Volume

(Cubic Feet) Percent

Difference

Millbrook Flatbrook Road Bridge

16.70 16.97 1.60% 31.70 25.87 20.25%

Brink Road Bridge 31.50 53.42 51.42% 68.90 69.55 0.94%

Model Results

Following calibration of the basin model, the precipitation depth for the 1-, 2-, 10-, 25-, 50- and 100-year storm frequency events were simulated. The 6-hour duration storm event was used for the 1-, 2- and 10-year storms, and the 24-hour duration storm event was used for the 25-, 50- and 100-year storms. Six-hour duration storms were used for the 1-, 2- and 10- year storms based on a calibration process for the channel bankfull discharge that considered observed bankfull flow data at the reference reach. Data for the reference reach used in this calibration is provided in the Wetlands Reference Site and Stream Reference Reach Report (WSP 2020). The runoff outputs of the HEC-HMS model for each storm event are presented in table 3. The HEC-HMS report summary is provided in appendix E.

TABLE 5. HEC-HMS RUNOFF OUTPUT BY SUB-WATERSHED/BASIN MODEL JUNCTION

Sub-watershed/

Basin Model

Junction Name

1-Year 6-Hour Storm

2-Year 6-Hour Storm

10-Year 6-Hour Storm

25-Year 24-Hour Storm

50-Year 24-Hour Storm

100-Year 24-Hour Storm

SB100 59.4 76.5 194.1 578.4 727.3 902.5

SB110 106.3 135.4 331.3 935.6 1162.3 1427.1

SB120 19.2 26.5 83.6 293.2 376.0 474.3

SB130 41.4 56.3 165.9 535.2 679.1 849.1

SB140 20.5 29.0 92.9 315.5 406.4 514.5

SB150 49.0 65.0 188.2 611.5 777.1 973.1

SB160 56.3 70.0 160.0 437.2 545.1 671.4

SB170 135.5 153.7 259.1 525.7 618.2 724.3

SB180 62.5 73.2 138.0 311.0 371.9 441.8

SB190 100.9 119.0 229.4 526.7 631.8 752.5

SB200 96.5 113.1 213.8 481.7 576.0 684.2

SB210 58.7 69.4 134.9 312.1 374.9 447

SB220 133.4 151.5 256.5 522.4 614.7 720.6

SB230 45.0 53.5 106.6 252.6 304.6 364.5

J100 165.7 211.8 525.4 1500.8 1869.1 2312.2

Sub-watershed/

Basin Model

Junction Name

1-Year 6-Hour Storm

2-Year 6-Hour Storm

10-Year 6-Hour Storm

25-Year 24-Hour Storm

50-Year 24-Hour Storm

100-Year 24-Hour Storm

J120 208.6 271.1 713.6 2205.8 2781.1 3454.8

J140 243.4 317.3 859.3 2752.9 3494.3 4357.8

Upper Bridge 253.3 330.6 879 2786.5 3580.9 4507.7

J170 268.3 344.8 910.3 2861.2 3673.9 4621.7

J180 274.3 349.4 926.6 2895.6 3722.3 4690.2

J190 306.3 363 940.6 2966.8 3756.4 4736.3

J200 326.5 381.2 956.3 2980 3810 4759.6

J220 427.4 509.3 1000.3 3076.9 3917.8 4943.3

End of Project Area 452.7 542.4 1082.9 3131.7 3990.1 5042.4

NOTE: OUTPUT MEASURED IN CUBIC FEET PER SECOND.

CHANNEL HYDRAULIC MODELING

WSP performed hydraulic modeling to analyze the effects of the proposed restoration on the stream hydraulics. The analysis compared existing and proposed condition models with a focus on water surface elevations, in-channel velocity, and in-channel shear stress. The hydraulic models were developed using the HEC-RAS river model program, version 5.0.7. Geometric input data for the HEC-RAS model were created using the RAS-mapper tool. Steady flow analyses were performed for mixed flow regimes under the 1-year, 2-year, 10-year, 25-year, 50-year, 100-year and Flood Hazard Area (FHA) flow conditions. The FHA flow is considered by the State of New Jersey as the 100-year 24-hour storm event with a 25% factor of safety added. Table 6 presents the discharge rates used by river station and HEC-RAS basin model parameter within the HEC-RAS model. Flow changes were used within the HEC-RAS model where new tributary inputs were observed in the project area.

Cross-section locations are presented with the data results of the hydraulic model in appendix F.

TABLE 6. DESIGN DISCHARGE RATES

Storm Event

River Station

(HEC-HMS

R140)

River Station

(HEC-HMS

Upper Bridge)

River Station

(HEC-HMS

J170)

River Station

(HEC-HMS

J180)

River Station

(HEC-HMS

J190)

River Station

(HEC-HMS

J200)

River Station

(HEC-HMS

J220)

1-Year, 6- Hour

179.90 189.40 199.60 206.20 255.30 275.60 352.10

2-Year, 6- Hour

315.80 330.60 344.80 349.40 363.00 381.20 509.30

10-Year, 6- Hour

778.40 809.50 838.20 852.00 869.30 874.60 932.70

25-Year, 24- Hour

2542.40 2650.00 2722.20 2755.3 2830.40 2836.80 2939.80

50-Year, 24- Hour

3308.10 3450.50 3540.80 3586.90 3627.70 3674.70 3773.30

100-Year, 24-Hour

4212.30 4384.90 4496.50 4562.70 4599.60 4634.20 4807.40

Flood Hazard Area

5265.38 5481.38 5620.63 5703.38 5749.50 5792.75 6009.25

NOTE: DISCHARGE IS PROVIDED IN CUBIC FEET PER SECOND.

Existing Conditions

The existing conditions hydraulic model was developed from combined topographic data, including a site-specific survey conducted by Dykstra Associates dated February 2020 and regional DEM data published in 2015 for outer…