Print this page Alternative Stormwater Management: Low Impact Development
Cory L. Horton, P.E.
Course Outline
This 10-hour course provides guidance for the application and design of the alternative stormwater management techniques of Low Impact Development (LID). The course content is based on the Prince George's County Maryland publication Low Impact Development Design Strategies: An Integrated Design Approach 1999 (150 pages). This publication introduces the goals of LID, presents the methodology of LID site planning, teaches how hydrologic methods can be used in LID design, and provides information to select and implement site specific integrated management practices.
This course includes
a multiple-choice quiz at the end, which is designed to enhance the understanding
of the course materials.
Learning Objective
This
course introduces the reader to alternative stormwater management techniques
of Low impact Development (LID). This course is intended for practicing engineers,
and others, who seek additional alternatives to conventional stormwater management
practices.
At the conclusion of this course, the student will:
- Understand what Low Impact Development is;
- Know the goals of LID;
- Be able to identify the differences between conventional stormwater managment and LID;
- Learn the principals of LID site planning;
- Learn the principals of LID soil erosion and sediment control;
- Learn about LID Integrated Management Practices (IMPs);
- Learn how to select IMPs based on site constraints; and
- Be presented
with sources of additional information.
Environmental
Effects of Urbanization
Urbanization causes drastic changes in the biological, ecological, and hydrologic
makeup of the land. Construction inevitably causes some degree of compaction
of the soil, the loss of vegetation density, the creation of impervious surfaces,
and the loss of bio-diversity. This in turn changes a watershed's response to
precipitation. The most common effects are decreased infiltration and evapotranspiration
and decreased travel time, which often significantly increases peak flows and
total runoff volume.
Water quality is also affected by urbanization. Increased flow during runoff
events and decreased flow during dry weather periods and have an adverse impact
on local surface waters. The loss of infiltration, and hence base flow, can
result in increased temperature and decreased oxygen available for aquatic life
in streams. Natural channels also undergo morphologic changes such as channel
widening, downcutting, and accelerated erosion when accommodating additional
runoff volumes.
What is Low Impact Development?
Low impact development is a relatively new site design strategy with the goal
of creating a post development hydrologic landscape that mimics pre-developed
conditions. Hydrologic functions of storage, infiltration, and ground water
recharge, as well as the volume and frequency of discharges are maintained through
the use of integrated and distributed micro-scale stormwater retention and detention
areas, reduction of impervious surfaces, and the lengthening runoff time (Coffman,
2000). LID also incorporates non-structural site design goals such as the avoidance
/ minimization of impacts to sensitive site features such as permeable soils,
steep slopes, wetlands, and flood plain areas.
How does LID compare to conventional stormwater management?
Conventional stormwater management (CSM) arose from the need to prevent downstream
flooding. CSM aims to limit peak flow rates by using macro-scale treatment measures.
In many ways LID aims to treat the problems at hand, rather than merely dealing
with the symptoms. Low impact development (LID) integrates ecological and environmental
considerations into all phases of urban planning, design, and construction.
Why is LID gaining Popularity?
The public and stormwater professionals are becoming aware that conventional
stormwater management is not addressing all of the impacts of urbanization.
LID is merely another viewpoint on stormwater management, that presents tools
to help minimize impacts to the environment.
Course Content
The purpose of this course is to provide guidance on the design and construction of LID. You will be directed to the U.S. Environmental Protection Agency website to study Low Impact Development: an Integrated Design Approach (1999 edition, 9MB 150 pages, PDF file format), which presents the methodology and design approach of LID site development. The link to the document is as follows:
Low Impact Development: an Integrated Design Approach
Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.
Table of Content
Chapter 1 - Introduction
Chapter 2 - Low-Impact Development Site Planning
Chapter 3 - Low-Impact Development Hydrologic Analysis
Chapter 4 - Low-Impact Development Integrated Management
Chapter 5 - Erosion and Sediment Control Considerations for Low-Impact Development
Chapter 6 -
Low-Impact Development Public Outreach Program
Course Summary
Low impact development
has the potential to address impacts from urbanization that conventional stormwater
management is currently neglecting. The use of microscale integrated management
practices has the potential for improving water quality, reducing runoff volume,
and mimicking the existing hydrologic conditions better than CSM.
Related Reading
For additional
technical information related to this subject, please visit the following websites
or web pages:
Low Impact Development
Center
Center for Watershed Protection
Stormwater Manager's
Resource Center
U.S. Environmental
Protection Agency
Prince
George's County, Maryland
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDHonline.com or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered professional engineer. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
