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~(JaD~! Thal~-Watershed Area link (T-Walk) The deepest part of the channel is called the "thalweg." The condition of the thalweg results from the interaction of stream physics and channel materials. The interactions are complex and driven by a host of factors including soils, geology, climate, human use, wildlife, topography, hydrology, vegetation, and natural disturbances. All of these can have profound effects on Stream Health factors such as pool depths and substrate. The "Watershed link" phrase acknowledges the stream's dependence on watershed processes and conditions. The tool introduced here is called T-Walk (Thalweg-Watershed Area linK) and is accepted by the Forest Service (1996) as a suitable method for determining Stream Health. However, the concern is not so much with determining Stream Health as it is in preventing the conditions that reduce Stream Health. Since it is generally cheaper to stay out of trouble than to get out of trouble, the primary focus for T-Walk is on advance wanning of upcoming problems so project activities can be modified before major costs for restoration (and litigation) have been incurred. In that context, T-Walk deals mainly with the physical processes that start with the land and end up in the stream. The first consideration is to implement land use practices that reduce the concentration of pollutants from land disturbing activities. As a practical matter, nearly any method that will disconnect disturbed areas or sediment sources from the stream network will be beneficial. Simple methods, such as sediment traps and vegetated filter strips, can prevent substantial stream damage with minor, if any, extra cost. T-Walk uses a 700 foot (200 meter) stream reach to characterize both habitat and substrate. Characteristics such as Tarzwell Substrate Ratios, thalweg depths, bank stability, bank vegetation, riffle insects, pools, and instream vegetation are all directly interpreted in light of the Stream Health Classes. With the emphasis on advance warning and physical processes, not all of the legal elements (Page 2) have been included, For example, T-Walk does not check for compliance to State water quality standards or identify changes in natural temperature or dissolved oxygen patterns. Nor does T-Walk directly measure effects within the biological and chemical systems such as organic accumulation and eutrophication. T-Walk contributes to the overall objective of water quality management by providing a system of evaluation and formal notification about Stream Health, adverse impacts, cost liability for restoration, proposed remedial action, and follow-up monitoring. Technical perspective is based on ecological integrity, rather than a parameter list, and incorporates influences of stream physics, channel materials, sediment deposition, and storm runoff characteristics. Text Page 12 .;' ,', 1 ",.