Habitat Conditions, Design Strategies,

Transcription

1 Habitat Conditions, Design Strategies, Coho on Cedar Ck. five years after analog-based stream restoration work. and Stream Classification In river work, computer modeling is an insidious procedure in which an air of surety hides questionable assumptions L.B. Leopold, 1997 What s in your Manning's n today? Photo by: DD 2005, Cedar Creek The weight of evidence wraps a tighter spiral around the most accurate answer. Presented by W. Barry Southerland, PhD Fluvial Geomorphologist WNTSC-USDA-NRCS

2 Rationale for this discussion To discuss structure relative to landscape setting To increase your understanding of pool wood cover complex To establish an understanding of channel hydraulics and wood Discuss design strategies to accommodate deeper pools with cover

3 What are the desired habitat conditions? Better question: Are the physical conditions present to support the desired habitat conditions? Brian Bair Diagram by BB, USFS

4 Desired habitat conditions Consistent local deposition and scour with cover and structure. How do we do this? Photo by WBS Photo by WBS Photo by WBS Photo by WBS

5 15 foot deep low flow White River, WA East Cascades by W. Barry Southerland Photo by WBS, White River, 2002

6 White River East Side: photo by W. Barry Southerland

7 Good intentions but not the way to deal with a gradient and habitat problem Johnson Creek, WA: 2005 photo by W. Barry Southerland

8 Planning the structure and not the system? Little Washougal River, WA, DD Little Washougal River, WA, DD

9 Designing structure and not the geomorphic Little Washougal, WA by DD system Little Washougal. WA by DD

10 High water Little Washougal by DD

11 When expensive structures fail Little Washougal, WA by DD Little Washougal, WA by DD

12 Little Washougal, WA by DD

13 W:D Ratio, T,, and Bernoulli s Principle τ WP A γw s τ d γw s Little Washougal Photo by WBS 2 lbs lbs / ft d 3 ft slope ( ft ft ) Little Washougal If slope and sinuosity are given relative to longitudinal profile in a design, what are we left with on the hydraulic geometry to appropriately affect pool depth and bedload transport? Answer: Width to Depth Ratio and the centrifugal force of the meander geometry relative to resistance

14 Bernoulli Relationship Too complex to model in a log cover complex, but conceptually it applies. A centrifugal component can be added. The degree of modeling complexity grows. p - pressure g - density z - elevation v - velocity g - acceleration of gravity Total Head (H) = p γ + z + v w 2 2 g v 2 2 g p =d γ ω E n e rgy Lin e W a ter S u r fa c e (EGL) (HGL) B o tt o m o f C h a n n e l Brian Bair z Datum

15 Log jam next to high W:D ratio, shallow pool Photo by WBS, Little Washougal

16 Structure design with or without analysis of local deposition and scour while maintaining bedload transport capacity.

17 The good news Current Stable Analog White River East side Cascades Photo by WBS

18 Complete restoration of severely perturbated stream corridors includes a temporal (timeframe) aspect to design that we are not capable of achieving in the short-term or instantaneously. To add complexity to this tenet, most stream restoration projects are implemented without much control over the contributing drainage area. Historical Analog East Side Cascades - Napeequa River Historical Analog West Side of Cascades Downey River Photo by WBS Photo by WBS

19 Dimensionless ratios are: three dimensional representations of a river morphology morphometric measurements including longitudinal profiles, cross-sections, planview morphology valley geomorphological relationships to meander geometry and profiles and so forth. Replication of dimensionless ratios results in a natural stable stream form yielding balanced bedload transport and increased fish habitat and riparian structure/diversity.

20 Analog Approach There is a miss-conception that the Rosgen Stream Classification is the design. Stream classification is to a Rosgen Analog Approach to restoration as to what a soil survey would be to a conservation plan or a holistic conservation measure design. Stream classification stratifies by similar form and predictable characteristics and provides a mechanism to extrapolate site-specific data to stream reaches having similar character. None of the this stratification precludes an extensive geomorphic design process that includes a comprehensive approach.

21 Analog Approach is it simplistic? Rosgen, 2005

22 Examples of several dimensionless ratios from a current stable morphological m C4 stream type used in design on East Slopes of Cascade Mountain Range Dimensionless ratios, i.e. C4 stream type on Cascade East slope in glacialfluvial troughs Profile Pool bankfull depth/average bankfull depth, ft/ft Riffle bankfull depth/average bankfull depth, ft/ft Run bankfull depth/average bankfull depth, ft/ft Glide bankfull depth/average bankfull depth ft/ft Cross-Section(s) Width to depth ratio riffle(s) Width to depth ratio pool(s) Width to depth ratio run(s) Width to depth ratio glide(s) Planview Sinuosity ft/ft Radius of curvature/meander belt width ft/ft Meander wavelength (times average bankfull width) Slope (water surface) Pool bankfull slope/average bankfull slope, %/% Riffle bankfull slope/average bankfull slope, %/% Run bankfull slope/average bankfull slope, %/% Glide bankfull slope/average bankfull slope, %/% Bed slopes Mean Range

23 What are the dimensionless ratios for the stable form relative to the specific reach of interest? C Channels B Channels A Channels Wildland Hydrology, 1998 modified 2006

24 Wildland Hydrology, 1996

25 Stream type Sensitivity to disturbance 1 Recovery potential 2 Sediment supply 3 Streambank erosion potential influence 4 Vegetation controlling A1 very low excellent very low very low negligible A2 very low excellent very low very low negligible A3 very high very poor very high high negligible A4 extreme very poor very high very high negligible A5 extreme very poor very high very high negligible A6 high poor high high negligible B1 very low excellent very low very low negligible B2 very low excellent very low very low negligible B3 low excellent low low moderate B4 moderate excellent moderate low moderate B5 moderate excellent moderate moderate moderate B6 moderate excellent moderate low moderate C1 low very good very low low moderate C2 low very good low low moderate C3 moderate good moderate moderate very high C4 very high good high very high very high C5 very high fair very high very high very high

26 Rosgen Interpretations Mgt.

27 Rosgen Interpretations Mgt.

28 Conclusion Cowlitz, 1996, WBS Hoh, 2005, WBS What goes around - comes around Hoh, 2005, WBS