TRCA Natural Channel Design Monitoring Program. SOSMART Group Meeting December 7, 2010

Transcription

1 TRCA Natural Channel Design Monitoring Program SOSMART Group Meeting December 7, 2010

2 Natural Channel Design (NCD) Reconstruction of a stream channel and floodplain using techniques to restore or replicate natural channel system form and functions; Principal objectives are: Mimic the self-sustaining geomorphic forms and processes of an undisturbed watercourse subject to the same watershedscale influences and local conditions; Support aquatic and riparian ecosystems of composition and quality that are reflective of an undisturbed watercourse subject to the same watershed-scale influences and local conditions.

3 Natural Channel Design is an Adaptive Management Problem Stream projects are designed with prior knowledge that they are experimental, risky, or may require modification later. Monitoring (and adaptive management) is the only means by which such adaptive projects can be implemented with confidence and accountability. -Adaptive Management of Stream Corridors in Ontario, MNR 2001

4 Evolving the practice requires monitoring and evaluation NCD involves complex and inter-related processes and remains experimental; In practice for 15+ years in Ontario with no evaluations of outcomes to date; Limits ability of proponents and practioners to evolve the practice Adaptive Environmental Management Process

5 Evolving the practice requires monitoring and evaluation We in the (U.S.) stream restoration world are currently in the untenable position of spending more than a billion dollars of taxpayer money a year on restoration projects with no real idea of whether or not they are succeeding. Thus supporters and critics of Natural Channel Design should work together to develop a broadly comparable national study evaluating the outcomes of restoration projects based on a variety of approaches. This should give a better sense of what combinations of available tools are working, and indicate the areas where practitioners and researchers need to work together to develop better tools -Rebecca Lave, The controversy over Natural Channel Design: Substantive Explanations and Potential Avenues for Resolution. Journal of the American Water Resources Association, December 2009

6 Natural Channel Projects in TRCA Number of projects: 40+ Project age: 0-18 years Length of affected streams: ~40 km Estimated expenditure: ~$40-50 million

7 NCD Monitoring Program Initiated in 2005, 10 year workplan examines 10 project sites in detail Sites range in age from 1 to 15 years post-construction; Evaluating performance in the context of stated and implicit design objectives; Comparing reconstructed (mitigated) reaches to undisturbed (control) reaches; Program design is based on TRCA Natural Channel Design Monitoring Protocol (2009); Lacking pre-construction biological data and as-built geomorphic surveys. Available at

8 NCD Monitoring Program Parameters assessed (3x over 10 yrs): Geomorphic characteristics (crosssections, longitudinal profiles, bank and substrate character., erosion pins); Engineered elements (functioning of riffles, pools, vanes, bioengineering, mitigation of fish barriers, etc.); Aquatic habitat and communities (fish and benthic invertebrates, OSAP); Riparian vegetation communities (ELC vegetation type and regional species of concern inventories); Amphibians and breeding bird surveys

9 NCD 5 Highland Creek, Toronto Constructed in 1997; 2 nd order stream; bankfull discharge of 2.5 m 3 /s Fully urban u/s drainage area with no SWM controls; 1800 m length, 60 m valley width Design objectives: Renaturalize straightened, Constructed in hardened channel and reconnect with floodplain; Appropriate aquatic and terrestrial habitats; Enhance aesthetics. Design features: Removal of gabions, add rock vortex weirs, plunge pools, crib walls, riparian wetlands, tree and shrub plantings.

10 Geomorphic objectives Most vortex weirs found to be functioning (2006) but some becoming buried by sediments or removed by high flows; Crib walls and flow deflectors generally performing as intended; Channel is still in-transition (degradation; widening) and will continue to undergo adjustments; Some outflanking of the constructed channel into riparian wetlands and formation of islands.

11 1999 (2 years post-construction)

12 2002 (5 years post-construction)

13 2007 (10 years post-construction)

14 Aquatic habitat objectives % in-stream cover is high (70%), composed of flat and round rock, no macrophyte cover yet established; Cool water fish community, mostly native and generalists, similar to u/s control; Species richness, catch per unit effort (CPUE) and index of biotic integrity (IBI) all suggest mitigated reach is providing equivalent quality habitat as u/s control; BUT u/s control represents an unimproved, impaired state! Mean Species Richness

15 Aquatic habitat objectives Benthic invertebrate data indicates poor stream quality (nutrient conditions) at both mitigated and control reaches (Hilsenhof Biotic Index Family level; HBI) %Worms, %EPT, and %Insects indicate that mitigated and control reaches are impaired; CONCLUSION: While habitat of equivalent quality as u/s impaired urban control is being achieved, no improvement from impaired state has been achieved yet. Mean HBI Score Very Poor Poor Fairly Poor Fair Good Very Good Excellent

16 NCD 8 Burndenet Creek, Markham Constructed in 1999; 1 st order stream; bankfull discharge of 3.3 m 3 /s Fully urban u/s drainage area with SWM pond; 900 m length, 60 m valley width Design objectives: Lower channel to accommodate Constructed in SWM pond outlet; Restore natural channel form and function; Rosgen E6 type channel; Appropriate aquatic and terrestrial habitats; Design features: Riffles, pools, fascines, on-line wet meadows, riparian plantings (tree, shrub and grass seed mix).

17 Geomorphic objectives Very little bed variability between riffles and pools; Channel becoming choked with vegetation; Bank erosion and slumping frequently observed - fascines not working or not present; Channel may be oversized; Channel is still in-transition (aggrading; widening).

18 Aquatic habitat objectives % in-stream cover is high (90%) and entirely composed of macrophytes; Cool water fish community, mostly native and generalists, similar to d/s control; Species richness, catch per unit effort (CPUE) and index of biotic integrity (IBI) all suggest mitigated reach is NOT providing equivalent quality habitat as control reach and is NOT positively contributing to watershed average. Mean Catch Per Unit Effort

19 Mean Index of Biotic Integrity Score Very Good Good Fair Poor 9-20

20 Aquatic habitat objectives Benthic invertebrates data indicates poor stream quality (nutrient conditions) at both mitigated reach, but fairly poor to fair at control reach (Hilsenhof Biotic Index Family level; HBI) %Worms, %EPT, and %Insects indicate that mitigated and control reaches are impaired; CONCLUSION: Both fish and benthic invertebrate data suggest aquatic habitat objectives not being achieved. Mean HBI Score Very Poor Poor Fairly Poor Fair Good Very Good Excellent

21 NCD 18 Morningside Creek, Toronto Constructed in 2003; 2 nd order stream; bankfull discharge of 3.32 m 3 /s Fully urban u/s drainage area serviced by SWM ponds; 1750 m length, 8-60 m valley width; Design objectives: Constructed in Realignment; Restore form and function of stream corridor Appropriate and diverse aquatic and terrestrial habitats. Design features: Vortex weirs, rocky ramps, riparian plantings with deep rooting native grasses (prairie cord grass), high root density plants on outside meander bends.

22 Geomorphic objectives Minor outflanking of riffles observed but >50% functioning (2006); Vegetation becoming established in channel; Beaver activity contributing to the evolution of the site BUT reducing survival of tree and shrub plantings; Channel is still in-transition (degradation; widening).

23 Aquatic habitat objectives % in-stream cover is 55% and >u/s and d/s controls, predominantly macrophytes, very little wood; Cool water fish community, mostly native and generalists, similar to u/s and d/s controls; Species richness, catch per unit effort (CPUE) and index of biotic integrity (IBI) all suggest mitigated reach is providing equivalent or better quality habitat as control reaches and positively contributing to watershed average. Mean Catch Per Unit Effort

24 Mean Index of Biotic Integrity Score Very Good Good Fair Poor 9-20

25 Aquatic habitat objectives Benthic invertebrates data indicates fair to fairly poor stream quality (nutrient conditions) at both mitigated and control reaches (Hilsenhof Biotic Index Family level; HBI) %Worms, %EPT, and %Insects indicate that mitigated and control reaches are impaired; CONCLUSION: Habitat of similar quality ( good ) as urban control reaches is already being achieved! Mean HBI Score Very Poor Poor Fairly Poor Fair Good Very Good Excellent

26 Terrestrial habitat objectives At all sites, immature meadow and plantation communities dominate, with some wetlands; Invasive species are relatively few and low in population (except NCD 11; 71% of veg com.) potential opp. to control them now; Plantings were mostly native species and survival has been moderately successful; Prairie cord grass planted at NCD 18 has been very successful; Highland Creek has the highest number of ELC vegetation types (19), naturally occurring flora species (204) and flora of conservation concern (27)

27 Terrestrial habitat objectives Several breeding bird species observed that are sensitive to urban development (local rank L4), including willow flycatcher, eastern kingbird, grey catbird, northern rough-winged swallow, and swamp swallow; Willow flycatcher recorded at 7 of 10 NCD sites monitored with a total of 17 territories noted best symbolizes an NCD site! American toads, green frogs and northern leopard frogs observed (all are local rank L3). Willow flycatcher Eastern kingbird Grey catbird

28 Overall conclusions All constructed channels are still in-transition BUT very few observations of complete failure to date; Some engineered elements are not functioning at most sites and are in need of maintenance; Biological monitoring suggests positive outcomes are being achieved over the short term opportunities remain to control spread of invasive plants; Disagreement between fish and benthic invertebrate data regarding quality of aquatic habitat, BUT still early in site evolution process; NCD sites already providing habitat for breeding bird species that are sensitive to urban development.

29 Overall conclusions Future NCD projects need more clearly stated design objectives on which to base evaluations of performance; Pre-construction biological data and as-built geomorphic surveys needed to better enable project evaluation; Consistent use of defensible and recognized monitoring methods and protocols is essential for comparisons between sampling events and project sites;

30 Next steps Continuing to monitor current 10 sites until 2015; Repeating full geomorphic assessments; Opportunity to examine evolution of habitats; Initializing new sites that include pre-construction and as-built monitoring; 5 year Progress Report to be completed in early 2011; Final report to be completed in Reports available at