Reconnaissance Level Assessment (RLA) Index
Overview: RLA is the first and most general of three phases in WARSSS assessment. This phase will help the assessor:
- Identify places in the watershed that represent likely sediment sources and channel stability problems, and thereby limit the effort and costs of the more intensive WARSSS phases
- Begin assembling and examining existing information
- Verify or, if needed, clarify or redirect the problem identification
- Eliminate sub-watersheds, reaches or areas within the watershed (e.g., stable slopes) that do not contribute excessive sediment
- Locate and focus on potentially important problem areas, reaches, or sub-watersheds for the next phase, RRISSC level assessment
Level of Difficulty: RLA is meant to be a very rapid, qualitative review of likely and unlikely sediment sources and problem spots in the watershed. A rough estimate of the level of effort for RLA on a third-order watershed is a few days. Because of its reliance on quick observation and expert judgment, RLA is best done by technical personnel very familiar with sediment sources, processes, and effects. Assessors working on this phase should be experienced in relating observations from topographic maps, land cover, soils, and geologic maps, aerial photographs, and field reconnaissance to effects on flow, hillslope erosion and channel processes and the identification of sediment sources and effects.
Getting Started in RLA: Completing RLA is not time consuming if the assessor has already made the following preparations:
- clearly identified on a map or GIS the exact water body and watershed with the sediment problem (Is it the whole river or just a specific reach? Are tributaries included? What is the exact drainage area that feeds the impaired part?)
- obtained monitoring information that indicates the impairment (If the reach is 303(d) listed, what data was used for this listing?)
- obtained the common, reconnaissance-level data sources called for in this methodology (topographic maps, recent and historical aerial photographs, land use/cover and soils maps)
You may wish to download and print out the RLA flowchart (PDF, 21 kb, 1 p.) to view as you follow the online steps, or download the complete RLA text and visuals (PDF) for off-line use.
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