CE-GY 7653 – Wetland Design for Water Quality Improvement Spring 2023

Title: Project 1 – Finderne Farms Mitigation Hydrology using HEC-HMS

Date: Friday, 24-February-2023 Due: Friday, 3-March-23

Description:

Use HEC-HMS (Hydrologic Engineering Center – Hydrologic Modeling System) to determine the rainfall/runoff component of a water budget for the Finderne Farms Wetland Mitigation site, Bridgewater, NJ. This analysis will be based on historic rainfall data that is available from the National Oceanic and Atmospheric Administration (NOAA).

Objectives:

• Use hydrologic tools discussed in this course for the rainfall component of the Finderne Farms Wetland Mitigation water budget.

• Further develop HEC-HMS modeling skills.

• Work with the concept of a ‘water budget’ design for a constructed wetland mitigation project.

Instructions:

1. Obtain historic precipitation data, follow Figures 1 and 2 as a guide.

https://www.ncei.noaa.gov/

Select a location: Manville, New Jersey “Manville 0.6 W, NJ US (US1NJSM0068)”

  Figure 1. NOAA, National Centers for Environmental Information.

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You must select   at the bottom right of Fig, 2.

Figure 2. NOAA, National Centers for Environmental Information

2. Create an Excel spreadsheet of the historic precipitation data (inches) for 2020. This Excel spreadsheet is one of the project deliverables.

3. Create a HEC-HMS for the Finderne Wetland Mitigation site.

The Finderne Farms site (0.28 mi2) varies in elevation from 31 to 36 ft and is therefore relatively flat (Figure 3). In addition to the Finderne subbasin include one Upland subbasin (0.10 mi2) that’s at an elevation of approximately 60 ft which is the industrial district accessed from Van Veghten Drive off of Finderne Ave. You should use observations from the site visit on Saturday, 18-Feb-23, and/or Google Earth to get an idea of your basins. You need to consider the precipitation collected from both the Upland subbasin and the Finderne Site subbasin together. You should not include a river “Reach” as part of your HMS model. Your HEC-HMS simulation should include a meteorological model with a specified hyetograph, a control specification, and time-series data with a precipitation gage. You need to determine the runoff from the site and the precipitation that remains at the site, i.e., retained in the soil and therefore accessible toward the wetland water budget for the “growing season”. The rainfall retained in the soil becomes part of the wetland water budget. You will need to visit the Web Soil Survey website:

 https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm

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Determine the soil type(s) at the Finderne site and use this information to determine appropriate parameters to code into your HEC-HMS model. Be sure to include the soils information in your write up.

The specific goal of this project is to compare the Snyder UH (unit hydrograph) method to the Clark UH method for runoff. Both of these methods will transform the excess runoff hyetograph to the runoff hydrograph. For the loss function leading to the excess rainfall hyetograph, use the SCS Curve Number for both the Snyder and Clark UH. Remember there is no river routing for this model. You will need to select appropriate values for the parameters needed to run the Snyder UH and Clark UH methods. Which one of the approaches would be more conservative for the purpose of a wetland water budget? In other words, which method may underestimate the amount of precipitation to the wetland?

Create an appropriate control specification. You will need to think about how to create the rainfall hyetograph to adequately reflect the monthly rainfall total. Assume a single rainfall event occurring within 1 day in any given month.

4. Once the HEC-HMS model is complete you can perform the simulation and examine the results.

5. Create a write up of your results from the hydrologic modeling in HMS. You should include the details of the techniques used, e.g., curve number values.

 Figure 3. Finderne Farms site (0.28 mi2) varying in elevation from 31 to 36 ft.

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Deliverables:

1) Please zip the HEC-HMS folder containing your model and email to [email protected]

2) The Excel spreadsheet with the monthly precipitation quantities (inches) for 2020.

3) A table of your results for the total quantity of rainfall (inches) retained in the soil for both subbasins individually within the “growing season” for 2020.

4) A write up that includes the hydrologic parameters used in you HMS model. You need to include the soil type(s) and how that led to your parameter selections. I need to clearly/easily understand how you set up your HMS model from your write up. Compare/discuss your results from the Snyder and Clark UHs for the Excess Volume.

Note:

i. A general discussion to supplement these instructions occurred in class on Friday, 24-Feb-23.

ii. I have tried to make these instructions as clear and complete as possible. Please ask if you feel something isn’t clear or if you think additional data should have been provided.

iii. Your final HEC-HMS model should not have extraneous components. A functioning model should be submitted without trial runs. I need to be able to open and understand your HEC- HMS model.

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