Estuary Assessment: Component XII of the Oregon Watershed Assessment Manual

This estuary assessment and prioritization method constitutes Component XII of the Oregon Watershed Assessment Manual (Watershed Professionals Network 1999). This module can serve as a stand-alone method, but is best used as a component of the larger assessment. Conducting a full assessment provides the best understanding of the watershed continuum from ridgetop to ocean.

Introductory material in this document describes the basic characteristics and functions of estuaries and tidal wetlands. Then, a series of seven steps make up the estuary assessment:

1. Use existing data, and generate new data, to determine the full historic extent of tidal wetlands within your estuary study area.
2. Use existing data, and generate new data, to identify alterations to tidal wetlands.
3. Define estuary analysis units based on alterations you have identified, and other site characteristics.
4. Identify and characterize conservation sites.
5. Identify and characterize restoration sites.
6. Identify land ownership for conservation and restoration sites.
7. Prioritize sites (within a given estuary) for restoration and conservation actions.

This module is lengthy, because it includes considerable material specific to estuaries. For example, the first step in the assessment is to locate the resources to be assessed (tidal wetlands) and determine the probability of tidal influence at each site. This module also contains a method for prioritizing sites, and special information on monitoring tidal wetlands.

Despite its length, this module is designed for use by someone with little familiarity with tidal wetlands. The benefits to your organization will be greatest if you conduct this assessment yourselves, rather than hiring a consultant. Many of the tasks are designed to build your understanding of the estuary, rather than merely produce an end result. Technical assistance may be helpful in particular phases of the assessment, but hiring a contractor to conduct the entire assessment will greatly reduce the benefit to you.

This assessment method was developed specifically for Oregon estuaries south of the Columbia River. For example, the method does not evaluate toxic waste disposal sites or sediment contamination, because industrial land uses are relatively rare in this region. By contrast, agricultural uses (including diking for pasture, ditching, and grazing) are covered in detail, because these are the most common alteration types found in the region. Like other components of the Watershed Assessment Manual, this estuary assessment is nonregulatory in nature and is not intended to replace or supersede existing land use planning regulations, inventories, or assessments.