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Integrated Design

Integrated Design. Key engineering concepts Conveyance, capacity of the channel to move water Reliability, capacity of the system to maintain itself and function without breakdown Safety, ability to avoid hazards and recover from upsets.

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Integrated Design

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  1. Integrated Design • Key engineering concepts • Conveyance, capacity of the channel to move water • Reliability, capacity of the system to maintain itself and function without breakdown • Safety, ability to avoid hazards and recover from upsets

  2. Linking Conveyance and Reliability to Restoration and Enhancement • Plant response to flows • How plants “react” to flow, how they steer flow • Modeling flood flows • How looking at roughness as a dynamic parameter changes the equation • Failure modes • Erosion • Overtopping, cracks, holes • Separating people from danger

  3. Plant-Water Interactions • Plant species • Branch density • Rigid/flexible/bending • Emergent/submerged • Scale • Plant scale/stand-reach • Leaf area index (LAI)

  4. Emergent/Submerged • Engineers love equations…..

  5. Rigid/Flexible/Bending

  6. Rigid/Flexible/Bending • Recent research with field tests of bending. • Modulus of elasticity estimated for tree species; natural materials exhibit high variability. From: Stone et al (2013)

  7. Rigid/Flexible/Bending • Bending characteristics estimated for flow velocities using vegetation-bending algorithm. • Results provide approach for predicting bending behavior; i.e., “dynamic” hydraulic roughness. From: Stone et al (2013)

  8. Energy Losses from Vegetation • Plant geometry • Topology • Age • Seasonality • Foilage • Volumetric/areal porosity • Density • Patchiness

  9. Hydraulic Roughness • Past – one value for entire floodplain, plants increase roughness • Current – multiple values for parts of floodplains, plants affect roughness +/- • Emerging – dynamic values accounting for velocity and depth, plants used to place roughness

  10. Manning’s Equation

  11. Variations in Hydraulic Roughness • Channel-floodplain hydraulic geometry • Flow depth and plant height • Plant age

  12. Hydraulic Roughness - Variations with Hydraulic Geometry • Depth in Channel and Floodplain From Chow (1959)

  13. Hydraulic Roughness - Variations with Hydraulic Geometry • Shearing effects and resistance from vegetation and topography slow floodplain overflows. • This, in turn, causes a reduction in the velocity of the flow in the main channel also and leads to a point when channel-floodplain storage is optimized.

  14. Floodplain Storage Optimization • Independent research indicates channel-floodplain storage is optimized when average channel and floodplain velocity is minimized at depth ratios of 1.2 > D/Dc > 1.6, where D = flood depth and = Dc bankfull depth. D= 19-feet Dc= 16-feet D/Dc = 19/16 = 1.2 From: Bhowmikand Demissie, 1982

  15. Hydraulic Roughness – Variation with Flow Depth and Plant Height • Hydraulic resistance varies with canopy height (CH) and foilage/branch density (FD). • Conceptually, as plants submerge roughness decreases from FD value to near novegetation (NV) value. • This neglects understory complexity, bending, etc. From: Anderson et al (2006)

  16. Hydraulic Roughness – Variation with Flow Depth and Plant Height • Four plant scenarios modeled using NWS FLDWAV (1D); 0.0m, 0.5m, 1.5m, 3.0m. • Bare earth n=0.043 and maximum n=0.150. • Weighted average approach of horizontal “slices” defined roughness variation with depth. From: Anderson et al (2006)

  17. Hydraulic Roughness – Variation with Flow Depth and Plant Height • Q2 and Q100 flood waves routed 60 km. • Peak flow attenuation greater for Q100 . • Rising limb flattens more for Q2 with more peak flow lag in various plant scenarios. From: Anderson et al (2006)

  18. Hydraulic Roughness – Variation with Vegetation Community Age • For the same flood stage, plants present a different hydraulic resistance during their life cycle – not addressed much in the literature! n2>n3>n1 n1 n2>n1 Colonization Juvenile Old Age

  19. Floodplain Definitions • Hydraulic floodplain - “The surface next to the channel that is inundated once during a given return period regardless of whether this surface is alluvial or not.” (Hydraulic Engineering Centre, 1976; Ward, 1978) • Genetic floodplain - “The largely horizontally-bedded alluvial landform adjacent to a channel, separated from the channel by banks, and built of sediment transported by the present flow-regime.” Nanson and Cooke (1992) • Polyphase floodplain – “The product of secular climate or other environmental (e.g. base level or land use) change.” Nanson and Cooke (1992)

  20. Floodplain Evolution • Floodplain terraces. From: Leopold et al (1992)

  21. Floodplain Evolution • Natural levees. From: Greenfieldgeography – Floodplain Mangement (2013) http://greenfieldgeography.wikispaces.com/Floodplain+management

  22. Update with Central Valley example From: Cook Inlet Wetlands (2013) http://www.kenaiwetlands.net/EcosystemDescriptions/Riparian.htm

  23. Floodplains and Groundwater From Malanson (1993)

  24. Floodplains and Microclimate From Malanson (1993)

  25. Floodplains and Water Temperature

  26. Changes in Land Cover Bay Institute, 2003 CWEMF – April 2013

  27. Changes in Hydrology CWEMF, April 2013

  28. Changes in Ecology CWEMF – April 2013

  29. Floodplain Functions

  30. Ecohydrology Management Concepts • Ecologically Significant Floods • Ecosystem Function Relationships • Seasonal Recruitment of Floodplain Vegetation • Survival of Floodplain Vegetation in Regulated Systems • Long-Term Seasonal Sustainability

  31. Ecologically Significant Floods • Large events are important geomorphically to create, disturb and maintain floodplain habitat. • Small/moderate longer duration events are important for species utilization. From: McBain and Trush (XXXX)

  32. Ecosystem Function Relationships

  33. Seasonal Recruitment of Floodplain Vegetation • xxx Mahoney and Rood, 1998

  34. Survival of Floodplain Vegetation in Regulated Systems From: Stillwater Sciences, 2006

  35. Long-Term Seasonal Sustainability USACOE HEC, 2009

  36. Additional Design Concepts • Natural levee emulation • Non-uniform floodplain levee storage • Strategic flow resistance schemes • Levee modifications

  37. Non-Uniform Floodplain Levee Storage and Levee Modification Concepts • Consider maintaining/modifying existing levees near river (similar to natural levees). Uniform Floodplain Levee Storage • Two-stage levees increase detention storage function of floodplain. (Jansen et al, 1979) Non-Uniform Floodplain Levee Storage

  38. Strategic Flow Resistance (Plan View) Establish tree plantings in “chevron-shaped” patterns on wide floodway areas to distribute and slow the movement of overbank flood flows.

  39. Flood Modeling Approach • Advantages of models in floodplain restoration design • Types of models • 1, 2 and 3 dimensional hydraulic models • What you need to build a model • Where you get the information • What the models show you/how to read the outputs

  40. Types of Models • Hydraulic [HEC-RAS, M11, M21, M3, Delft3D] • Ecological [HEC-EFM, ??] • Biological [RIVER2D, ??]

  41. 1, 2 and 3 Dimensional Hydraulic Models • Differences • Advantages/disadvantages • Simplification of complex systems

  42. Differences Between 1, 2 and 3D Models Source: Colorado Floodplain and Stormwater Criteria Manual (Chapter 12) CWEMF – April 2013

  43. Differences Between 1, 2 and 3D Models NCHRP-106, 24-24, Criteria for Selecting Hydraulic Models, December 2006 CWEMF – April 2013

  44. Differences Between 1, 2 and 3D Models NCHRP-106, 24-24, Criteria for Selecting Hydraulic Models, December 2006 CWEMF – April 2013

  45. Differences Between 1, 2 and 3D Models NCHRP-106, 24-24, Criteria for Selecting Hydraulic Models, December 2006 CWEMF – April 2013

  46. Differences Between 1, 2 and 3D Models CWEMF – April 2013

  47. Depth-Varying Roughness

  48. Examples Feather R Plant mosaic

  49. Example Feather River maintenance

  50. Example FR safety (from previous showing potential erosion hot spot)

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