SI-4D (12/1/04 version)
Watershed-Based Options To Address Stream Integrity Impairment: Intervention Options
As noted in the overview, once the feasibility of intervention is analyzed, step 8 of the stream integrity design process involves evaluating and selecting intervention options. For the purposes of the NPS Plan 2005-2010, "intervention" refers to a conscious local decision to implement either active or passive mechanisms to allow formation of a self-sustaining stream channel.
Table 1, summarizes the two key stream morphology stressor indicators that are used to develop alternative stream integrity restoration approaches. Table 1 identifies WHAT needs to be done, whereas the Active and Passive Restoration Methods sections below provide more detail on HOW these approaches can be accomplished.
||Alternative Restoration Approaches
|Vertical Channel Stability
- Identify and manage root causes of channel instability;
- In channel grade control
- Actively change or allow existing channel form to passively change;
- Lower ground elevation adjacent to the channel;
- Raise stream bed elevation;
- A combination of the above;
Passive Restoration Methods
Given the high cost of in-stream channel restoration, and the relatively few hundreds of feet that have been restored each year, passive stream recovery offers the most economical model for improving basic stream morphology. The passive restoration approach focuses on identifying locations where stream recovery is already occurring and facilitating continuation of that recovery. For example, in some cases, bank erosion associated with re-meandering streams or building floodplains is a key feature identifying a location where passive restoration is warranted.
Some examples of passive restoration methods are listed below.
- Riparian Corridor land set asides - through purchase, conservation easements, zoning ordinances and/or stream protection legislation. The purpose of the set-aside is to eliminate encroachment and permanently protect the area necessary for floodplain and/or stream channel recovery. The amount of set-aside needed can be calculated based on the target morphology (the best shape and elevation of the stream and floodplain) identified through the assessment process. In urban areas, set asides may already be necessary to address green-space, flood control, and stormwater management needs, providing a ready opportunity to incorporate stream integrity into the equation.
Floodplain "Higher Standards" package (ODNR, Division of Water) provides information about incorporating broader stream quality goals into local/FEMA flood management programs.
- Potential Stream Restoration Site Inventory - includes data regarding relative need for restoration, potential actions needed to resolve stream morphology issues, and ranking of both, ecological potential and relative potential for restoration. Creating such an inventory may attract funding from entities that have commitments to mitigate or restore stream sites due to a previous regulatory action.
Active Restoration Methods
Active stream restoration approaches generally involve earthmoving either into or out of the stream channel/floodplain. They may also include grade control structures such as riffles, cross veins, and W-weirs, selective planting or removal of streamside vegetation, ditch maintenance to provide a two-stage channel, and/or dam removal or modification. A wealth of information about specific practices is available in Stream Protection, Lowhead Dam Removal and Active Channel Restoration section of the management practices and measures section. Case studies for some active restoration methods are available. Additional stream restoration examples are available at the STREAMs website created and maintained by the Ohio State University as "... a multi-agency initiative whose goal is to provide education, information, technology and communication on stream management strategies."
Increasingly, changes to watershed hydrology during development are increasing the bed-load transport ability of urban streams, thereby starting a cycle of channel incision. Consequently, USEPA instituted the Phase II Stormwater Control Program which includes requirements for stormwater controls during and post-construction. By targeting more frequent runoff events for detention (less than 1 year recurrence interval), bed-load sediment transport rates are better controlled. Information about specific stormwater practices is available in the Construction Site Storm Water Control and Rainwater and Land Development sections of the management practices and measures section.
Targeted Education and Outreach
To successfully restore and maintain self-sustaining stream channels in Ohio, it is essential to target stream integrity outreach and education to streamside property owners, county/municipal engineers, service directors, and consulting engineers. The vast majority of stream side miles will continue to be privately owned. Many local governments actively manage miles of stream channel. Therefore, buy-in from local landowners and land managers will be necessary to achieve stream morphology targets. They in turn rely on the services of consulting engineers who design the local projects that occur in the riparian corridor. Recommendations regarding a targeted education and outreach strategy will be provided by the Management Practices Technical Advisory Group.