River Restoration, 2018 Has stormwater management been our Achilles Heel in River Management?

Transcription

1 River Restoration, 2018 Has stormwater management been our Achilles Heel in River Management? By Bill Annable, PhD, PhD, PEng, PE, PGeo Department of Civil & Environmental Engineering, University of Waterloo The Canadian Rivers Institute, Fellow Supervising Professor Ecole Polytechnique Federal de Lausanne, Switzerland

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3 Flow release culvert under dam buttress in Rome Henry Darcy Fountain (Flow control) Dijon, France Stormwater Management India Roman stormwater management, Portugal

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5 Current Stormwater Management Strategies (and variants thereof) 90 Discharge (m 3 /s) Unregulated Event Peak Shaving at 2-year Return Why do we keep following this path? Time (hours)

6 Kind of

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8 The quantification and management of bed material transport is still not considered in any holistic fashion in SWM design Elevation NAVD 88 (m) Deposition Erosion Crosley Creek outfall Sweigert Creek outfall Sediment basin Channelization Erosion or Deposition (m) aggradation/degradation ( ) River Station (m)

9 Channel evolution model (Modified from Schumm et al., 1984) Stage I. Quasi Equilibrium (h<h C ) Stage IIa. Degradation (h<h C ) Stage IIIa. Degradation & (h>h C ) Widening h floodplain h h h Stage IIb. Widening (h<h C ) h slumped material Stage IIIb. Degradation & (h>h C ) Widening h Stage IV. Aggradation and Widening (h>h C ) terrace h Stage V. Quasi Equilibrium (h<h C ) bank bankfull terrace aggraded material aggraded material

10 Fundamentals (Stokes Law, 1851) 1.0 m/s 0.1 m/s 7.2 minutes 6.6 days

11 Do we consider the water a nuisance/pollutant or a resource?

12 New (Old) Ways of controlling water and sediment at source

13 Results Patrick Lindemann

14 River Thur, Switzerland Removal of levees and allowing natural processes to reinstate.

15 San Jose, California

16 Guadalupe River, San Jose (2000) Expropriated Properties

17 Guadalupe River, San Jose (2015)

18 Are there quasi urban stream channels and what are there characteristics? Sault Ste. Marie Preliminary Screening Region U.S.A. Detroit CANADA Ontario Toronto b) Niagara Falls Quebec Ottawa U.S.A. a) b) 0 25 km Hamilton L. Ontario Toronto 8 12 Niagara Falls Canada U.S.A. * Population of approximately eight million in the greater Toronto and surrounding areas

19 Stream (and storm sewer) channel length versus effective catchment area Stream network length (km) Effective catchment area (km 2 ) Rural Urban Urban (with storm sewers)

20 Peak Event Discharge

21 Median annual frequency of bankfull discharge (or greater) (Annable et al, RRA, 2012)

22 Bankfull return period versus watershed urban land use (Annable et al, RRA, 2012) Rural Urban Bankfull 1.5-yr recurrence interval, T bf (years) Urban land use (%) <= bankfull <= 32 yr recurrence interval, Weibull or Log- Pearson should not be used on urban streams.

23 Effective Discharge Analysis Effective Discharge (Meyer-Peter Muller) Yield (Tonnes) Yield (Tonnes) Classes Classes Effective Discharge (m 3 /s) :1 3 Yield (Tonnes) Classes Discharge (m 3 /s) Banfull Discharge (m 3 /s) For floodplain connected streams Never for incised channels

24 Bedload Rating Curves of 12 Urban Streams in southern Ontario, Canada (Annable et al., 2012, RRA) Most Urban (12) (8) (1) (7) (9) (3) Bedload Discharge (kg/s) Observed Rating Curve (5) (6) (2) (11) (4) (10) Least Urban Discharge (m 3 /s)

25 Changes in bed material sediment supply with landuse change (Annable et al., 2012, RRA) Exponent a) Yield (Tonnes) Urban Land Use (%) b) Effective Catchment Area (km 2 )

26 Discharge Pulsing Q Ci / Q bf (-) Q c50 /Q bf Q c84 /Q bf Urban land use (%) Number of annual events Q c50 Q c Q bf Urban land use (%)

27 Bed Material Tracking (Plumb et al., WRR, 2017) Morphological Surveys (Form) Longitudinal profiles Cross sections Diagnostic bed sampling Sediment Tracking / Sampling (Process) Bedload measurements (Helley-Smith) Inter-event-based particle tracking (RF- ID transponders) Longitudinal inventories Floodplain relief Bank heights Riparian vegetation Water surface characteristics (flood flow) Infrastructure Upper Left: RF-ID Tag Right: Morphological Surveys using GPS Lower Left: Helley-Smith Sampler

28 Coarse particle mobility relative to measured morphology (Morphological units travelled) >50% of mobile particles remained on original morphological feature Majority of remainder travelled 1-2 morphological features

29 Riffle and pool characteristics Increased number of pools between bends Surveyed Thalweg D BF H R Regression analysis at bankfull stage D P H RP L R Surveyed bankfull elevation Vertically Exaggerated L RP L IP Riffle are shorter and steeper

30 Change in Morphology - Elongated meander wave lengths, - Typically two or three riffles on a straight section between bends separated by intermediate pools, - Riffles are commonly observed to be ( )W bf not a Leopoldian (2 3)W bf, - Riffles are also steeper and more armoured (often comprised of failed rip-rap revetments, Changes in bedforms are manifestations of changes in hydrology, sediment supply/transport and energy dissipation.

31 Urban Condition Increased frequency in low magnitude floods and of shorter durations, combined with Decreases in bed material supply and decrease in grain sizes (with the exception of anthropogenic material), are resulting in smaller urban bankfull channels to maintain channel stability, however, larger floodplains are required to attenuate flood flow energy. (relative to the pre-development condition) Increased floodplains Decreased main channel width

32 Red Hill Creek Watershed Land Use (85% urban land use) Lake Ontario

33 Site conditions

34 What Was Approved in km of concrete lined channel 19 Bridge Crossings

35 Design Previously Proposed and Approved (1985) 5.5km of concrete lined channel 19 Bridge Crossings (14m spans) Destruction of fish habitat Estimated Construction cost: $13.8 Million (Cdn) Designed / Constructed ( ) 7.2 of creek channel using NCD techniques (0.0km concrete lined channel) 9 Bridge Crossings (min. 32m spans) Increased diversity in fish habitat Elimination of combined sewer overflows Excavation of 230,000 m 3 of material from the valley walls (banks) to accommodate floodplain function Final Construction cost: $7.2 Million (Cdn)

36 FIRST LAW OF RIVER REHABILITATION: To successfully construct a river rehabilitation project, the river reach must be designed with: FS < 1.0! The channel must be designed to fail (in a strict engineering risk sense) in a controlled fashion to maintain dynamic stability(i.e. Dynamic vs. Static Design) This is, after all, how a natural river functions.

37 Channel alignment and site images So = 3.2% Before After So = 1.7%

38 Channel alignment and site images Before After So = 0.4% So = 0.3%

39 Channel alignment and site images So = 0.6% So = % So = 0.6% Before After

40 July 26, 2009 Location Simulated Peak Flows (m 3 /s) Comparison of July 26, 2009 Storm Response to 100 year Event and Hurricane Hazel 100-Year Storm Event (Based on Continuous Simulation) Regional Storm (Hurricane Hazel) July 26, 2009 Storm Event (Using Radar Rainfall) Percentage of 100 Year Storm Event CNR % Davis Creek at Mt. Albion Rd % King Street % Albion Falls %

41 Stage (m) July 25, 2009 Preliminary Stage Data Red Hill Creek, Hamilton, Ontario July 26, 2009 July 27, 2009 Mt. Albion Barton St Time

42 Upstream Widened Sections range between: 16m 21m Sections still demonstrating quasi-stable characteristics range between (Annable, 1994): 8m 10m. Evidence of Downcutting

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44 Annual Centre Line Migration

45 All-in-all Method 2009 Flood 2012 Flood Overall Lateral Erosion Cross sectional Area 58 Sections > 0.3 m 34 Sections < 0.05 m 34 Sections > 0.3 m 35 Sections < 0.05 m 0.18 m/yr 40 Sections > 1.0 m 2 18 Sections > 1.0 m m 2 /yr 22 Sections < -1.0 m 2 6 Sections < -1.0 m 2 Centre Line Migration 33 Sections > 0.3 m 70 Sections < 0.05 m 10 Sections > 0.3 m 67 Sections < 0.05 m 0.10 m/yr And the target design rate of channel migration was estimated to be 0.07 m/ yr* * - reconstruction occurred on sub-reaches (steepest reach and downstream of infrastructure) where erosion rates were greater than 1.0m after the 2009 and 2012 floods.

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47 Finland - The construction of peat land drains to lower the water table to harvest peat for incineration in industrial and residential heating

48 Finland - Has lead to downcutting, deposition and the covering of spawning habitat

49 Increase in drainage density network (and sediment supply) from agricultural drains

50 Discharge (m 3 /s) Discharge (m 3 /s) McKenzie Creek Day (July and August) Day

51 Agricultural drains: Increased erosion, reduction in base flow leading to downstream sedimentation. Continued maintenance costs. Restoration vs. rehabilitation? Has there been a base level change? Has the hydrology (frequency and duration of bed material moving) events changed?