Restoration

• Currently, a huge topic, not only with respect to contaminated rivers, but degraded rivers in general;

• Current federal initiatives call for the restoration of 25,000 miles of stream corridor and the re-establishment of 2,000,000 miles worth of conservation buffer zones; Also 100,000 acres of wetlands (USEPA, 2000).

• This will cost millions of $$$

Original Definition(after Berger, 1990)

• Restoration is the structural and functional return of a degraded riverine ecosystem to its pre-disturbance condition.– Goal is to emulate a natural functioning, self-

regulating system that is integrated with the ecological landscape in which it occurs.

• The pre-disturbance condition is generally considered to be the state of the river prior to European settlement (in the U.S.); Commonly considered the Bronze age in Europe.– Several problems with the assumption.

Problems with Using Pre-Settlement Conditions as Restoration Goal

• The Pre-Colombian ecosystems are assumed to be those that are healthy; this may or may not be true;

• This idea objective can rarely be achieved because (after Hobbs and Norton, 1996):– We do not generally know what the structure,

function, composition or dynamics of these ecosystems was like;

– Even if we did, the pre-disturbance condition may not fit the modern stable state(s) because the system has evolved.

Alternate Definition (USEPA, 2000)

• Restoration is the return of a degraded ecosystem to a close approximation of its remaining natural potential.

– Based on the idea that you can only restore the ecosystem to what the climate, geology, hydrology, etc. will support.

– So, determine what was once there, what the environment will now support, and then develop realistic objectives regarding how the degraded system can be moved to a direction of what it will support. (very different from original definition).

Use of Alternative Definitions

• Rehabilitation (Waal et al., 1998): A process which can be defined as the partial functional and/or structural return to a former or pre-degraded condition or putting back to good working order.

• Some significant advantages for the use of this definition, but it is not applied much in the U.S.

Are Restorations Successful?

• Numerous successes have been described in the literature (National Resources Council, 1992; FISRWG, 1998), but it is recognized that riverine ecosystems are extremely complex and their response to physical and biological manipulations are not easy to predict. (i.e., there have been a lot of failures!)

• In fact, Kondolf (1995) argues that restoration projects should be viewed as experiments from which we can learn from our successes and failures

Lack of Scientific Approach• Current restoration projects are not being done in

a very organized, coherent method.

• For example, Hobbs and Norton (1996) cogently argue that

• “restoration ecology has largely progressed on an ad hoc, site-and situation-specific basis, with little development of general theory or principles that would allow the transfer of methodologies from one situation to another. This is illustrated at the international level by the editorial by Majer & Recher (1994), which shows little cross-fertilization of ideas between different localities.”

Basic Steps in Stream Restoration(after Interagency Handbook)

• Getting organized

• Identifying the problems and opportunities

• Developing goals and objectives

• Selecting and designing restoration alternatives

• implementing, monitoring, evaluating, and adapting the project.

Goals and Objectives

• Goal is more encompassing. It defines what you want the state of the river to ultimately look like. They should naturally be consistent with the problem/opportunity identification data (i.e., problem-opportunity statements).

• Objectives are more specific. Focus on specific factors that can be produced to achieve the stated goals.

• Unrealistic goals can generate unrealistic expectations and potential disenchantment amount stakeholders when those expectations are unfulfilled.

Setting Goals and Objectives(Three Components)

• Define the desired condition of the future system.

– It represents the ideal situation for restoration, whether or not this reference condition is attainable.

– This ideal has been given the name “potential” and is considered to be the highest ecological condition or state that a stream can attain, given no political, social, or economic constraints (Prichard, et al., 1993).

Setting Goals and Objectives(Three Components)

• Identify the scale of the project, and the scale at which impacts may impact the system.

– For all systems, watershed scale processes influence the river. Need to start here.

– If the channel is being disturbed upstream and downstream of the site, is it reasonable to proceed.

– How stagnate is development; will the watershed look the same in 10 years as it does today. If not, how will this affect the system.

Setting Goals and Objectives(Three Components)

• Identify constraints and issues that must be considered.

– These are things that constrain the methods that may be used in the project. They consist of both technical and non-technical factors.

– Technical: generally related to availability of data, likelihood of stabilizing a given area, based on our current expertise with the a particular problem.

– Nontechnical are more numerous and readily recognized. May include, Political/social: conflicting land-use or water use issues: grazing, logging, fishing, public access, etc.; Financial issues, Legal issues such as Permits, or issues regarding property ownership, easements, and zoning.

– Physical: existing structures – roads, pipelines, powerlines, etc.

– For contaminated rivers, also need to consider areas which may not have been remediated.

Selection of Restoration Alternatives

• The alternative that is selected should accomplish the restoration goals and objectives, and, therefore, solve the identified problems within the limits provided by the restoration opportunities.

• Must always consider whether you are treating the causes or symptoms. Treating the symptoms may result in other, unwanted impacts.

Alternative Types

• No action: System will heal itself, for does not merit intervention.

• Nonstructural techniques: broadly defined as any restorative method that does not involve either physical alterations (e.g., realignment of the channel, riprapping, etc.) of the river or construction of a dam or some other structure (NRC, 1992).

• Structural: Intervention of the current river processes of form using physical materials or structures.

Types of Structural Approaches

• Soft engineering – refers to the use of locally available natural materials such as woody debris and alluvium. Restore to natural conditions using natural stuff.

• Hard engineering – hydraulic engineering approach, which typically optimizes for one use (e.g., flood conveyance, drainage, etc.) and utilizes concrete, sheet pilings, riprap, or other imported materials.

• Biotechnical engineering: channel or bank modification methods that use vegetation in a variety of innovative ways.

From Interagency Handbook

Root Balls

RockWeirs

Log/WillowErosion Structures

Headcut Structures

WillowFences

From Rosgen, 2003

Cross Vane

Rosgen, 2003

Additional Considerations to the Alternative Selection Process

• Identification of possible alternatives that exist. Must include no action.

• Analysis of how cost-effective it is. Requires two types of data:

– Estimates of the alternatives net benefits (output). – Estimates of costs. More readily determined.

• Risk assessment: No matter what alternative is ultimately selected, there is always a certain amount of risk that the project will fail. The potential for failure should be evaluated.

Channel Design and Reference Reaches

• In some cases, it may be advantageous to entirely or partly reconstruct a channel from scratch.

• Channel should be constructed to transport the available water and sediment delivered to the system without causing significant erosion or deposition.

• Reconstructing a channel from scratch is an extremely complicated process, and there are multiple methods of attacking the problem.

LakeChristopher

Erosion Control Project

(Tahoe Basin)

Channel Breaching, 1995 Flood

ExcavatedChannel

Reference Reach Approach

• Can be based on either:– Biology: reach with desired biological

conditions, which will be used as a target to strive for when comparing various restoration options.

– Geomorphology: reach that serves as a template for the geometry of the restored channel. The channel morphology is transferred either exactly or by altering scale to fit them to reaches with slightly different characteristics (e.g., basin size).

Use of Regional Curves

From http://www.ncsu.edu/sri

From http://www.ncsu.edu/sri

Problems Inherent in the Use of Reference Reaches

• Most associated with the difficulty of identifying suitable reference reaches.

1. Must have similar geology, relief, size, rainfall, and land cover.

2. Must have similar land-use histories

3. Curves assume that bankfull is the dominant discharge. This may or may not be true.

4. Assumes that the that hydrology and sediment load characteristics of the disturbed basin are the same as the stream to be restored.

Stream Classification Systems(Uses)

• As a communications tool.

• Provides a framework for analyzing data. It can be argued that streams that fall within a certain class will function similarly and therefore can be analyzed together.

• Provides a means of understanding the variability that may exist for selected parameters such as channel size, shape, pattern and classification.

• Placing a stream of interest into a particular category, may allow use to gain important insights into how that stream or river functions.

Disadvantages of Using a Classification Approach in Restoration

• They are based on channel characteristics at one specific time – the time of analysis. Therefore, the dynamic condition of the stream is not directly indicated by the classification system.

• The river response to a perturbation or restoration action is normally not determined from classification alone.

• Biological health of a stream system is usually not directly determined from a geomorphic classification system.

Rosgen ClassificationFrom Rosgen, 1996

Important Comment

• Most academics will state that classification systems, including Rosgen’s, should be used cautiously and only for establishing some of the baseline conditions on which to base initial restoration planning.

• Interagency Handbook states, “Standard design techniques should never by replaced by stream classification alone.”

Table from NRC, 1992

From W.M. Davis to Rosgen???

• While there is a lot of talk surrounding the whole system, the classification system of Rosgen is generally applied at the reach scale. Thus, it draws attention away from a systems approach, and focuses on a specific reach.

• Represents a cookbook method that is commonly linked to evolutionary schemes that may or may not be valid for a particular stream of interest.

• Ignores that river processes are a function of that system’s history.

• Suggests that all rivers behave the same, regardless of climatic/hydrologic regime, geology, etc. For example, commonly stated that it applies to arroyos as it does to any other type of river. This is simply incorrect.