Habitat Assessment

Overview

The habitat evaluation process involves rating many different habitat conditions as optimal, suboptimal, marginal or poor based upon criteria (descriptions and a rating scale) included on the survey data sheets. The optimal category is a description of conditions that meet natural expectations; suboptimal includes descriptions of criteria that are less than desirable, but satisfies expectations under most circumstances; marginal is a description of moderate levels of degradation with severity at frequent intervals throughout the reach; and poor are descriptions of criteria for streams that have been substantially altered with severe degradation characteristics. Descriptions of the habitat conditions are provided below. For additional information go to Chapter 5 of the US EPA's Rapid Bioassessment Protocols Manual. The conditions here should be applied when describing the habitats of rocky-bottom streams and rivers.

Resources

• Rapid Bioassessment Protocols

  U.S. EPA's Rapid Bioassessment Protocolas manual.

• Level 1 Habitat Assessment

  This portion of the survey discusses general physical observations, making several judgments based on established rating descriptions, as well as some collection and measurement procedures.

Embeddedness refers to the extent to which rocks (gravel, cobble, and boulders) are surrounded by, covered, or sunken into the silt, sand, or mud of the stream bottom. Generally, as rocks become embedded, fewer living spaces are available to macroinvertebrates and fish for shelter, spawning and egg incubation. To estimate the percent of embeddedness, observe the amount of silt and sand sediments overlying and surrounding the larger gavel and cobble size particles. You should base your embeddedness assessment on the composition of the materials that you observe. Embeddedness is always evaluated in the riffles used for your macroinvertebrate collections. In most cases the best person(s) to comment about this condition is the person(s) collecting macroinvertebrates. If cobble and gravel are easy to remove from the riffle and there is little sand or silt either in the net or suspended during collections, embeddedness is minimal. In some cases chemicals can cement (armoring) the substrate together and cause severe embeddedness.

Riparian buffer width is an estimate of the width of natural vegetation from the edge of the stream bank out through the riparian zone. The vegetative zone serves as a buffer to pollutants entering a stream from runoff, controls erosion, and provides habitat and nutrient input into the stream. A relatively undisturbed riparian zone supports a robust stream system; narrow riparian zones occur when roads, parking lots, fields, lawns, bare soil, rocks, or buildings are near the stream bank. Residential developments, urban centers, golf courses, and rangeland are the common causes of anthropogenic degradation of the riparian zone. Conversely, the presence of old fields, paths and walkways in an otherwise undisturbed riparian zone may be judged to be inconsequential to altering the riparian zone and may be given relatively high scores.

Riparian buffers are the most valuable protection a stream system has against outside influences. In most cases healthy riparian directly reflects upon the condition of the stream unless the source of the insult is a specific pollutant. Enhancement of the riparian buffer by re-planting native grasses, forbs, shrubs and trees is the first step in the recovery of the stream back to a more natural condition. Some of the benefits of a healthy riparian buffer include:

• Provides organic material as food for invertebrate, fish and wildlife
• Supplies large and small pieces of woody debris that provide habitat for fish, invertebrates and amphibians
• Alters how sunlight reaches the stream and is an important temperature moderator
• Stabilizes stream banks and reduces erosion
• Filters sediment and materials from overland runoff and roots of many plants traps and holds the sediments
• Absorbs nutrients from overland and sub-surface flows
• Reduces the impacts of flooding through temporary storage, interception/diversion and slow releases (especially wetlands) from heavy rain