Low-order stream channels in northern California forested watersheds are a special management problem. They are numerous, high gradient with steep sideslopes, difficult and dangerous to traverse, and constitute the most sensitive lands in all watersheds. Hillslopes adjacent to most low-order streams are typically steep, deliver eroded materials directly to channels, and have landslide-prone "valley inner gorge" morphology (Figures 1 and 2).

Knowing the extent and characteristics of the low-order streams in a planning watershed is critically important information - but is difficult to obtain and therefore usually missing. When such information is gathered, it has commonly been localized (e.g., the channel directly below a cut unit or at a road crossing), and a watershed-wide picture cannot be drawn.

As an part of our Coordinated Resource Inventory (CRI) - which includes the mapping of soils, geology, and vegetation, all at once - we are trying to develop practical techniques for mapping and describing all stream channels in a survey area. The large streams are easy - they are not extensive and are often described in fish habitat surveys. The small streams are the big challenge.

We had two primary questions:

"What techniques for stream channel and streamside slope mapping can produce a useful picture of the most sensitive lands in a planning watershed?"

"What does it take, in time and money, to complete a useful inventory of all stream channels and streamside slopes in the steep, dissected forested watersheds common in northern California?"

We assembled an interdisciplinary group and brainstormed what characteristics we were interested in. We then pared the list down to what seemed to be a practical minimum set of characteristics to measure. We then set out to survey all the streams in a 15,000-acre survey area, in the Bluff Creek watershed near Orleans California, which is tributary to the Klamath River. Streams were defined as:"any channel or declivity showing evidence of annual scour or deposition".

The survey technique divides the stream into short, successive sections based on geomorphic and riparian characteristics. Thus each section contains relatively consistent features. Mappable features within each section are:

• Stream gradient
• Flow (P,I,E)
• Inner gorges (length and slope)
• Channel bankfull width
• Valley bottom width
• Riparian vegetation (width and species comp.)
• Woody debris volume, by size class
• Channel bearing

• Inner gorges, valley bottom width, stream gradient, and bankfull width - a 50% change in either the width, length, or slope
• Riparian - a 100% change in width of the riparian vegetation zone
• Bearing - a 25o change
• Mouth of tributaries
• Change in flow (i.e., perennial to intrmtnt.)

No map is prepared in the field, but aerial photos are carefully referenced and control points are noted in the data. A schematic of a map can be prepared from the data (Figure 3). Automated map generation from a spreadsheet of the data is under development.

Data analysis and integration with geology, soils, and vegetation information, and application of GIS is underway. Many of the channels mapped are difficult or impossible to discern on aerial photos. Therefore, the technique can provide detailed information concerning stream protection and sensitive areas that is otherwise unobtainable. As a first-cut, we believe that this technique is practical, but needs to be refined to reduce the amount and/or resolution of data taken to increase production and decrease costs.

Production

You can contact Sam and Mike at (707) 441-3551 FTS 448-3551