Print this page Wetland Restoration & Enhancement Design
John Poullain, P.E.
Course Outline
This three-hour online course discusses the engineering surveys, hydrology and geotechnical data that are necessary for the design of wetland structural components, fish passages, water control structures and levees to meet the wetland functions. It covers the various classes of wetlands, characteristics, objectives and hydrodynamics. Engineering, biology, and geology, soil science and other disciplines used for designing a feasible wetland project. Restoration actions and activities performed at wetland sites must comply with federal, state and local regulations to protect water quality and the environment.
This course includes a multiple-choice quiz at the end, which is designed to
enhance the understanding of the course materials.
Learning Objective
At the conclusion of this course, the student will have covered these topics:
- Basic science, functions and purposes of wetlands;
- Wetland processes – physical, chemical and biological;
- Hydrodynamics of wetland systems;
- Wetland types and characteristics;
- Engineering survey data required- types and scope;
- Geotechnical and geological investigation data required;
- Soil characteristics and suitability for levees and water control structures;
- Hydrology data needed for analysis – precipitation, ground water, runoff, etc;
- Properties of control structures and fish passages;
- Design of water control structural components;
- Design of vegetation, types, suitability for function of wetland;
- References and sources of information for the objectives listed above; and
- Federal, State and local policies to consider for required regulations and environmental restrictions.
This course is intended for civil engineers, project managers, planners and owners.
Benefit to Attendees
The student will understand the basic procedures for designing a wetland restoration or enhancement project and its components. Topics covered include the science, characteristics, and functions of various classes of wetlands. Wetlands are used to reduce erosion, and to control runoff of sediments onto down gradient land and downstream water. They also reduce pollutants since groundwater and surface water may be contaminated with volatiles, soluble organics, corrosive acids and alkalis.
Course
Introduction
Wetlands are used to manage the movement of storm water and sediments at construction sites, improve water quality, and retain floodwater, recharge groundwater and to protect commercial or residential areas from storm-driven waves and tides. Hurricane protection is reduced as wetlands are lost and more open water appears. Other benefits of wetlands are the creation of wildlife and fish habitats for commercial and recreational purposes.
Wetlands have many names – freshwater and saltwater marches, bogs, sloughs, swamps, bottom lands. They are in-between places, which lie between large bodies of water, coastal areas, lakes and streams and dry land. They are defined as areas inundated by surface or ground water at frequencies and duration that support vegetation adapted to saturated soil conditions. Although all wetlands are not “wet” all year, drier wetlands have significant benefits.
In addition to the above-mentioned methods for wetland development, there are also wetland restoration projects and environmental enhancement projects. The purpose of these projects is to maintain or revive former wetland areas by diverting stream flows and mimic spring floods. Levees are normally built for flood protection. In these cases however interior water levels are regulated with gated structures to provide conditions that would naturally occurs. Gated gravity drainage structures are built into existing river levees to divert sediment-laden river water in a controlled manner and flood the landside marshes. The goal is to allow deposition of sediment load and nutrients as was performed naturally before levees were built. The technique is beneficial in restoring wetlands, which have subsided or eroded.
The wind erosion occurring during the “dirty thirties” fostered early soil conservation efforts. These first measures were aimed at soil conservation but as land development increased, runoff erosion and sedimentation became issues also. Remedial actions include stormwater control like constructed wetlands to prevent off-site migration of surface water, sediments and pollutants which can contaminate the soil, groundwater, wells and nearby bodies of water unless properly managed. Sediment washed downstream contains soil particles along with petroleum products, metals, chemicals, corrosive acids, pesticides, organics and other pollutants.
Based on volume, sediment from erosion may be a larger pollutant of waterways and lakes than is toxic waste or chemicals. In cases where the National Pollutant Discharge Elimination System (NPDES) for stormwater permits applies, a Stormwater Pollution Prevention Plan (SPPP) is required for construction sites. State and local governments also have regulations that require special precautions for land-disturbing activities.
Erosion occurs naturally but is accelerated by land development and land use changes. Increased urbanization, with increased roof areas, pavements and the clearing of woodland and grassland without proper conservation management create erodible land areas, speed up runoff and remove areas available for rainfall infiltration. Vegetation removal from land areas will further accelerate erosion and siltation.
Vegetation - Site specific conditions must be considered to use vegetation. Success of vegetation depends on the climate characteristics, slope grades, site preparation, water and watertable elevation and compatibility of vegetation with these conditions. Vegetation is one of the most commonly used methods for stabilization of stormwater dikes and in some cases containment dikes. It is relatively easy to maintain and establish and properly selected plants and grasses are self-maintaining. Erosion control matting may be necessary to hold the seed and soil in place until the vegetation is established.
Vegetation protects a slope with the roots and exposed branches, stems. Surface flow velocity is reduced and the capacity for infiltration and water withdrawal from the soils is increased. Seedbed preparation, fertilizers, planting dates, rates of application and type of grasses will depend on the region, specific area for planting, time of year and as specified in the design plans. Also there are temporary and permanent plantings. Nurse crops such as cereal grains are sometimes uses in the seeding mix.
Course Content
This course is based on Chapter 13 (Section 650.1304 Design, pages 38 to 96) and Appendix 13A of the US Dept. of Agriculture NRCS Engineering Field Handbook, “Wetland Restoration, Enhancement, or Creation”, Part 650, (2008 Edition 68 pages), PDF file.
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.
Course Summary
Among the factors considered for wetland restoration and enhancement are the physical, engineering and chemical characteristics of various types of wetlands and feasibility for the site. Key to designing a feasible plan is to understand the problem and objectives of the wetland site. Attempting too many functions may not be successful. This course also considers the benefits wetlands provide for controlling soil erosion and sediment and protecting water quality. State and federal regulations have to be complied with at wetland project sites in order to remove any threat to public health or the environment.
References
For additional technical information related to this subject, please refer to:
http://el.erdc.usace.army.mil/wetlands/guidebooks.html
USACE has developed regional handbooks for wetland assessments across the US.
http://www.epa.gov/owow/wetlands/wetland.html
US EPA “Americas Wetlands: Our Vital Link Between Land and Water”. The site gives a broad overview of wetland types, values, successful projects and protection efforts.
Quiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center 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 architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
