Unit 2.1: Hydrologic Impact of Land-Use Change

Overall learning objective for this activity: Students will be able to model the impact of land-use change on the hydrologic cycle.

Specific learning objectives for this activity:

1. Students will be able to use the EPA's National Stormwater Calculator to model the impact of development on stormwater runoff.
2. Students will be able to compare the relation between rainfall and runoff data from different land use scenarios, one representing pre-expansion and the other post-expansion relative to a residential neighborhood.
3. Students will be able to assess the role ecosystem services associated with permeable land covers, like forest cover, play in regulating the hydrologic cycle.

This activity is designed to be used in conjunction with the Unit 1 activities to evaluate the change in stormwater runoff in the context of lost ecosystem services. It may also be used alone as an introduction to the EPA's National Stormwater Calculator (Calculator) from which the impact of land-use change on runoff can be analyzed quantitatively. This activity would be appropriate in a range of introductory courses in water resources, sustainability, ecology, environmental science, Earth science and geology, land-use planning, anthropology, and landscape design.

The activity is designed for students to work in groups using the Calculator. Either student laptops or university/college computers can be used for the activity, but the Calculator must be installed. The link is provided in the References and Resources section below. Because the Calculator downloads soils data from a national database, Internet access is required. Not every student needs a computer for this activity, but at least one computer must be available per group.

Class Size: This activity can be adapted for a variety of class sizes.
Class Format: This activity is designed for individual lecture sessions, but it is suitable for use in a lab setting or as a homework assignment as well. Students can work together, in groups of 2–4, but each student should complete his/her own assignment.
Time Required: This activity is designed to be completed in a 50-minute class period.
Special Equipment: Student groups should have a computer running Windows that has access to the Internet. The Calculator, which runs only on Windows, must be installed from the Internet. The link is provided in the References and Resources section below. Because the Calculator downloads soils data from a national database, Internet access is required during this activity. Not every student needs a computer for this activity, but at least one computer must be available per group. From the instructors' experiences, having at least one computer per three students is ideal.
Skills or concepts that students should have already mastered before encountering the activity: This activity assumes familiarity with basic concepts of ecosystem services and the hydrologic cycle.

Prior to class, students should read the fact sheet produced by the U.S. Geological Survey called Effects of Urban Development on Floods (Acrobat (PDF) 111kB Jun14 15), available also at USGS. They should also read the one-page technical fact sheet (Acrobat (PDF) 396kB Jun14 15) on the EPA's National Stormwater Calculator. It is also available at EPA.

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Permeability of Different Land-Cove Types

Provenance: National Land Cover Database/USGS
Reuse: This item is offered under a Creative Commons Attribution-NonCommercial-ShareAlike license http://creativecommons.org/licenses/by-nc-sa/3.0/ You may reuse this item for non-commercial purposes as long as you provide attribution and offer any derivative works under a similar license.

It is assumed that the Calculator has been downloaded and installed on the instructor's computer and on a computer available to each student group. The URLs for the program and users guide are included in the References and Resources section below. Instructors should be familiar with the calculator prior to class, downloading it on their computer for presentation, perhaps having skimmed the user's guide for a functional knowledge of the program or having at least worked through the tutorial. Following a short introduction to the program by the instructor, students will follow the Unit 2.1 Tutorial (Microsoft Word 2007 (.docx) 5.6MB Dec1 16) to model the impact of a proposed development on stormwater runoff.

A particular Calculator location file is used in this activity so that the instructor and students are all working from the same baseline site information. To download the location file, click on Thomaston Trail Expansion.swc (ShockWave Component (SWC) 1kB Jun19 15), and select Save File, and then "OK." The file will be downloaded into your computer's Downloads folder as "thomaston_trail_expansion.v3.swc." It can then be opened from within the Calculator as described in Part 1 of the Unit 2.1 Tutorial (Microsoft Word 2007 (.docx) 5.6MB Dec1 16). Students will complete the exercise by answering the questions about their work and the data they collected in the Unit 2.1 Assessment (Microsoft Word 2007 (.docx) 16kB Sep4 16).

Introduction to Urban and Suburban Development (10 min)

Impermeable surfaces associated with urban and suburban development (i.e., roofs, sidewalks, driveways, roads, parking lots) produce greater stormwater runoff than permeable surfaces associated with other land uses. Unit 2.1 Presentation (PowerPoint 2007 (.pptx) 11.3MB Sep4 16) provides a series of slides that can be used to illustrate the problem:

1. increased runoff (conceptually using percentages, with data using the water-balance data from Unit 1);
2. impact on streamflow (changes in the streamflow hydrograph); and
3. impact on water quality.

Additional slides introduce students to different land covers and their varying levels of permeability, going from the aerial image which they have had some experience with via Google Earth, land cover from the 2011 National Land Cover Database (NLCD), and estimated percent impermeability from the 2011 NLCD (the latter two determined by remote sensing from satellite data).

Introduction to the EPA's National Stormwater Calculator (20–40 min, depending how the Calculator is introduced)

Transition from the PowerPoint presentation that addresses the problem to the EPA's National Stormwater Calculator (Calculator) that provides part of the solution. The Calculator provides a means for its intended users (site developers, landscape architects, urban planners, and homeowners) to evaluate the impact of land-use change on stormwater runoff. Its intended uses are for analyzing changes in hydrology at the screening or planning level, assessing long-term performance of stormwater management practices, and identifying practices that can help meet stated performance goals (e.g., minimal hydrologic impact). It is not intended for construction‐level design. In the tutorial and assessment materials accompanying this unit, students are being considered urban planners, analyzing the changes in hydrology that will result from expansion of a residential area into an area that is currently forested.

A short YouTube video about the Calculator from the EPA is a simple transition.

Instructors should be familiar with the Calculator prior to class, downloading it on the instructor's computer for presentation, perhaps having skimmed the user's guide for a functional knowledge or having at least worked through the tutorial. If the first and last of these have been done, there are a couple of ways to introduce the Calculator and its use:

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The EPA's National Stormwater Calculator

Provenance: Ed Barbanell, University of Utah
Reuse: This item is offered under a Creative Commons Attribution-NonCommercial-ShareAlike license http://creativecommons.org/licenses/by-nc-sa/3.0/ You may reuse this item for non-commercial purposes as long as you provide attribution and offer any derivative works under a similar license.

2. Assign the tutorial for in-class work, and help students work through it in real time. If this alternative is chosen, the remainder of the class session should be devoted to this. If students finish early, they should answer the questions at the end of the tutorial.

Use of the Calculator (0–20 min, depending how the Calculator is introduced)

Assign the Unit 2.1 Tutorial (Microsoft Word 2007 (.docx) 5.6MB Dec1 16). Spend a minute on the problem outlined at the beginning of the tutorial. What is critical here is that development of the forested area is assumed to be consistent with the development that has already occurred. That is, the ratio of permeable to impermeable surface is similar, lot size and homes are similar, and they are uniformly spaced. That will be important to highlight again in discussion related to Unit 2.2 and implementation of Unit 2.3.

Give students time to work through at least the pre-development scenario from the tutorial for use as baseline data. They will record their results in the Stormwater Calculator Tutorial Results Table (Microsoft Word 2007 (.docx) 19kB Jun20 16), referred to as Table 1 in the tutorials. If students finish their modeling effort early, they will complete the exercise by answering the questions about their work and the data they collected in the Unit 2.1 Assessment (Microsoft Word 2007 (.docx) 16kB Sep4 16).

If students do not complete the modeling, assign the remainder of the work and answering the questions in the Unit 2.1 Assessment (Microsoft Word 2007 (.docx) 16kB Sep4 16) for homework. Alternatively, a part of the next class session can be used to complete the work.

Students have used the Calculator to model changes in stormwater runoff. Their ability to analyze the results and their understanding of the implications relative to ecosystem services are assessed based on their answers to the questions assigned in the Unit 2.1 Assessment (Microsoft Word 2007 (.docx) 16kB Sep4 16). Answers can be turned in for grading or simply checked by the instructor for completeness. Students' answers can be a basis for class discussion in the next activity to evaluate student learning. A key is included:

Unit 2.1 Assessment Key -- private instructor-only file

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National Stormwater Calculator User's Guide Version 1.1

Description and download page for National Stormwater Calculator

Green Technology Webinar Series—Stormwater Management: Low Impact Development and Greening Corporate Grounds