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TS3E Rosgen Stream Classification Technique

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TS3E Rosgen Stream Classification Technique Technical Rosgen Stream Classification Supplement 3E Technique—Supplemental Materials (210–VI–NEH, August 2007) Technical Supplement 3E Rosgen Stream Classification Part 654 Technique—Supplemental Materials National Engineering Handbook Issued August 2007 Cover photo: The Rosgen stream classification system uses morphometric data to characterize streams. Advisory Note Techniques and approaches contained in this handbook are not all-inclusive, nor universally applicable. Designing stream restorations requires appropriate training and experience, especially to identify conditions where various approaches, tools, and techniques are most applicable, as well as their limitations for design. Note also that prod- uct names are included only to show type and availability and do not constitute endorsement for their specific use. (210–VI–NEH, August 2007) Technical Rosgen Stream Classification Supplement 3E Technique—Supplemental Materials Contents Purpose TS3E–1 Data requirements TS3E–1 Stream reach TS3E–1 Plan view (planform) type and level I classification TS3E–1 Valley types .......................................................................................................TS3E–2 Channel slope—level I ....................................................................................TS3E–2 Morphological description (level II classification) TS3E–2 Channel slope—level II ...................................................................................TS3E–9 Bankfull discharge validations .......................................................................TS3E–9 Entrenchment ...................................................................................................TS3E–9 Channel material ..............................................................................................TS3E–9 Width-to-depth ratio ......................................................................................TS3E–14 Sinuosity ..........................................................................................................TS3E–14 Procedure TS3E–14 Interpretations and uses of the Rosgen stream classification TS3E–14 Stream management ......................................................................................TS3E–16 Channel evolution ..........................................................................................TS3E–16 Planning stream restoration measures .......................................................TS3E–16 Communication ..............................................................................................TS3E–16 Prediction ........................................................................................................TS3E–16 Trends and dominant processes ..................................................................TS3E–18 Conclusion TS3E–20 (210–VI–NEH, August 2007) TS3E–i Technical Supplement 3E Rosgen Stream Classification Part 654 Technique—Supplemental Materials National Engineering Handbook Tables Table TS3E–1 Plan view characteristics of Rosgen stream TS3E–2 types Table TS3E–2 Aerial and surface views of major stream types TS3E–4 Table TS3E–3 Valley type, morphological description, and TS3E–8 stream type association Table TS3E–4 Stream morphometry and landform TS3E–15 Table TS3E–5 Summary of delineative criteria for broad level TS3E–17 classification Table TS3E–6 Summary of characteristics of Rosgen stream TS3E–19 types by watershed conditions Figures Figure TS3E–1 Major stream types TS3E–3 Figure TS3E–2 Hierarchical level II key TS3E–10 Figure TS3E–3 Measuring stream gradient TS3E–11 Figure TS3E–4 Field measurement of entrenchment ratio TS3E–11 Figure TS3E–5 Entrenchment ratios of major stream types TS3E–12 Figure TS3E–6 Pebble count TS3E–12 Figure TS3E–7 Plotted particle size distribution TS3E–13 Figure TS3E–8 Evolutionary stages of channel adjustment TS3E–18 TS3E–ii (210–VI–NEH, August 2007) Technical Rosgen Stream Classification Supplement 3E Technique—Supplemental Materials Purpose Data requirements Rivers are complex natural systems. A classification The Rosgen stream classification can be met through system is often used to stratify river reaches into a hierarchical assessment of channel morphology groups that share common physical characteristics. measured based on bankfull dimensions. In order, the A stream classification system provides better com- hierarchical attributes are: munication among those studying river systems and • single-threaded or multiple-threaded channels promotes a better understanding of river processes. The river classification system presented in this tech- • entrenchment ratio nical supplement is based on measurable physical • width-to-depth ratio parameters. • sinuosity The stream classification presented in this technical • slope supplement is condensed from the more detailed ver- sion by Rosgen (1994). It is intended for planning pur- • material size D50 median particle size bed material poses, but is not sufficient for design. Appropriate data for use in river classification systems can be obtained from simple measurements and estimates. Stream reach The objectives of the Rosgen stream classification are to: The classification applies to segments or reaches of the stream as defined by the user. However, any given assimilate a relatively complex mix of math- • stream reach should be comparatively uniform in its ematical relationships that describes a type of physical and biological characteristics. river and simplifies it into a system that can be understood Stream reaches can be defined from U.S. Geological • provide a consistent and reproducible frame of Survey (USGS) 7.5-minute quadrangles, aerial photo- reference for those working with river systems graphs of appropriate resolution, and confirmed by and communicating stream morphology among field reconnaissance. Soil and geologic maps may also a variety of disciplines and interested parties provide helpful information for delineating stream and enable people to talk in common terms reaches. about streams • predict a river’s behavior from its appearance and better understand cause and effect rela- Plan view (planform) type and tionships (the specific measured stages in chan- level I classification nel evolution models) • provide a mechanism to extrapolate site-spe- Level I classification is related to basin relief, land- cific data to stream reaches having similar char- form, and valley morphology. This broadest character- acteristics ization level is used only where general classification is required. The dimensions, patterns, and profiles are • encourage thinking about stream processes relative to channel evolutionary changes and based on information from topographic and/or land- trends form maps and aerial photography. The intent of level I classification is for a broad characterization that inte- • provide a tool to define a target such as the grates landform and fluvial features of valley morphol- stable reference reach or desired form to aid in ogy with channel relief pattern, shape, and dimension departure analysis and for setting objectives for (table TS3E–1). restoration or rehabilitation (210–VI–NEH, August 2007) TS3E–1 Technical Supplement 3E Rosgen Stream Classification Part 654 Technique—Supplemental Materials National Engineering Handbook A geomorphic characterization describing A through G Valley types stream types completes the level I classification. The stream type is based upon the measures of the stream Stream type, width-to-depth ratio, sinuosity, entrench- in plan view from topographical or ortho-digital maps ment, and other morphological features are dependent (fig. TS3E–1 (Rosgen 1996)). The plan view is classi- upon the valley development. For an initial broad level fied as straight, sinuous (meandering), sinuous with association of stream types, valley types are invaluable active point bars, or braided (numerous intertwining to level I classification and as a general indication of channels separated by longitudinal and/or transverse morphological pattern. Table TS3E–3 provides more bars). Some reaches may have actively eroding banks, detailed description of the 11 valley types used in the anastomosing (multiple narrow and deep channels Rosgen stream classification system. with extensive well-vegetated bars and flood plains), tortuous (extremely contorted meanders), or highly sinuous low width-to-depth bankfull channels. Channel slope—level I Aerial photographs of sufficient resolution to show the Over substantial distances, elevations, and channel plan view of the channel bed are good tools depend- lengths can sometimes be determined from a com- ing on the channel size and age of air photos. Judg- bination of USGS 7.5-minute quadrangles and aerial ments should be verified by field reconnaissance, since photos. Aerial photographs can be used to calculate channels are dynamic and can change their plan view sinuosity. Thus, slope can often be calculated by first character over time. Photographs and field observa- multiplying sinuosity times stream length from the tions are best obtained at times of low flow and opti- quad maps, then second, by dividing the difference in mum visibility. Flood stages or vegetation can mask elevation by the total sinuous stream length. important features from observation and could result in misidentification of the plan view type. A general longitudinal profile, which can be inferred from topographic maps, serves as the basis for break- ing the stream reaches into broad slope categories that reflect profile morphology.
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