Riparian Restoration
CHAPTER 4: RESTORATION PREPERATION
The goal of riparian restoration is to set in motion a process that enables natural ecological processes to reestablish themselves and to continue. The essence of riparian restoration is working with nature rather than trying to change or control it. To accomplish this goal requires being acutely aware of the area’s natural characteristics, its natural functional and structural elements, including but not limited to climate, soils, weather patterns, hydrology, plants and wildlife, and also being aware of socioeconomic use patterns.
Good planning will make or break any project, especially one as complicated as a restoration project. Planning must encompass any aspects, whether grand or minute, that might impact the site.
An interdisciplinary (ID) team is necessary for a riparian restoration project. It is essential to clearly delineate riparian characteristics through science-based field assessments. The team must gain a thorough understanding of the restoration site, its associated problems, and of how these problems are affecting the site and other natural processes in the watershed. The team also needs to know how current and proposed recreational activities might affect the site and surrounding areas.
When assessing the restoration site (sometimes called a site analysis), the ID team should address the assessment holistically, assessing upstream and downstream conditions, lateral and vertical conditions, conditions of areas surrounding lakes and other water bodies, and their connections to the restoration site. The team should conduct initial planning assessment at a broad watershed scale and graduate to collecting information at a project-specific scale. Such assessments will help determine whether a problem is unique to the site or symptomatic of other problems in the watershed. Planners, designers, and other members of the ID team should seek long-term solutions to the problem rather than using a “quickfix” that treats only symptoms.
Understand Existing Conditions
In the early stages of project planning, a field assessment conducted by a team of specialists can clearly identify the riparian ecosystem and the outside influences that contribute to its health or infirmity. This assessment clearly defines which ecological functions and processes must remain undisturbed during and after any potential construction and/or restoration projects. With this approach, protection of riparian structural and functional characteristics automatically becomes part of the planning, design, and construction processes.
To help understand the structure and function the site may have had, the ID team should use a reference site to compare, in the simplest of terms, a functioning, intact site with the project site. The reference site can be adjacent to the damaged site, a short distance away, in the same watershed, or in a different watershed with similar ecosystems. It needs to have characteristics similar to the project site, such as soil type, aspect, topography, geology, stream patterns and profile, weather patterns on lakes, and climate.
To analyze the reference and restoration sites for differences and commonalities, the ID team should consider the following factors:
- Historical records
- Historical written
records and
photographs to the present for analyzing social and economic trends
and use patterns, including indigenous peoples, pioneers, and settlers.
- Aerial photographs
for
comparing images from different decades or years.
- Climate
data from Government
land office surveys, old journals, dendrochronology (treering
analysis), pack rat middens, and palynology (pollen analysis).
- Topographical
maps.
- Land-use
patterns including farming, ranching, housing, and recreation.
- Proper Functioning Condition reports (DOI 1998).
- Adjacent communities and activities
- Adjacent conditions of upland and
riparian habitats and how their conditions may be affecting the reference
and restoration sites.
- Hydrologic responses, such as percolation tests
and water storage differences between degraded and natural sites.
- Depth-to-dry-season water table, which may vary during the day, thus requiring readings at the same test sites morning, noon, and evening to determine water depth. (Water table depth profoundly influences the ability to restore riparian structure and function.)
- Soils
- Site-specific soil survey to provide site productivity
information such as nitrogen, calcium, and phosphorous content; percent
of organic matter; and so on; physical properties (for engineering
purposes); and water-holding capacities.
- Soil type variability across the
site.
- Soil moisture variability across the site.
- Hydrology
- Water quality
to determine the presence of toxic chemicals, such as herbicide
residues, aquatic
macroinvertebrates, and periphytons (communities of microorganisms
that are associated with various aquatic substrates).
- Stream and
watershed health (Regional 1995;
USDA FS 1989).
- Annual hydrograph.
- Flood regime—time-of-year of flooding, length of time of overbank flooding, and frequency of flooding.
- Vegetation
The ID team should use transects of the reference site to inventory the benthic macroinvertibrates, vegetation species frequency (plant species composition), woody species density, and woody species age classes. The team should use references such as DOI BLM1992; USDA FS 1989; Bonham 1989; and Myers 1989.
- Canopy—coverage and health.
- Root structure.
- Characteristics such as old
growth, even age, and so on.
- Dead and downed material.
- Litter.
- Root zone functioning.
- Plant composition—The ID team should note closely the plant variety differences
at the
water’s edge or ecotone where the riparian ecosystem blends with the upland species
as compared to the middle of the site and look for the ecotones within the riparian
ecosystem. Plant species on terraces, which mark abandoned flood plains, will
be different from those on flood plains because soil moisture in the terrace
is probably lower than on the flood plains.
- Visibility of species during only
part of the year; for example, annuals.
- Identity of all threatened
and endangered species.
- Habitat for specific animals—migratory and resident.
- Wildlife
- Bird populations.
- Identity of which birds customarily use
the project site
during breeding
season, as a way to gauge riparian health. If birds
are absent, the site
may have been
altered to an extent that makes it uninhabitable.
- Identity of all threatened and endangered species and their habitat
niches.
- Identity of migratory and residential use.
In some areas of the country, it may be difficult to find a reference riparian ecosystem that has naturally occurring processes that support riparian structure and function. For instance, the native vegetation may have been removed for farming and then left fallow.
What grew back may not be native riparian vegetation, nor would it necessarily have a riparian structure to support ecosystem functions. Information gleaned from historical accounts, soil analysis, an adjacent watershed, and the flood regime would indicate what the land was capable of supporting. Local botanists and native plant societies can suggest appropriate plant selections to achieve ongoing ecosystem function.
Project Goals and Objectives
The ID team should determine the project site’s future condition (FC) based on its analysis. It should set the FC for what the project site is ideally capable of supporting. Forest plans generally have a broad FC, while a site’s FC is specific.
To achieve the FC, the team should set project goals and objectives, which at a minimum should support the proper functioning conditions of the riparian and watershed ecosystems (Prichard 1998). A goal is a general broad statement of purpose and direction that supports or is an element of the FC. For example, a goal might be to restore natural riparian ecosystem processes to the site by reestablishing riparian function. Goals, which deal with distant timeframes, can be achieved but cannot be “done.” Objectives, which are more immediate, are a series of steps or activities to be done that lead to the accomplishment of goals (Rieger and Traynor 1998). They are measurable.
The drawings in figures 50 and 51 show how to use a site analysis and good design to sustain riparian structure and function. The same principles are also useful in evaluating current conditions and/or restoring an existing site.
Click image for descriptive view
Figure 51—Design Principles
E-mail: 