Being inspired by problems and opportunities with instream structures

1. Being inspired by problems and opportunities with instream structures Using Water Framework Directive to create a better environment for people, fish, wildlife and angling – a framework for community action in the field of water policy Dominic Martyn dominic.martyn@environment-agency.gov.uk Environment Agency South East Principal Officer – River Basin Planning River Basin Planning and Ecology

2. A quick question please Please raise your hands if you have attended any Darent and Cray community meetings before?

3. Overview Why are structures built How our learning is developing Structures – impacts and opportunities In practice – removing and mitigating effects Questions throughout?

4. Some thoughts Me? water via jam jars and fishing for 25 years… Today – questions, address some concerns, hopefully be inspired and see options on some of your structures helping you and wider society Good habitats mean healthy fisheries and ecology – resilient to changing climate, flood, pollution and predators Future society? Depleting natural fish stocks and loss of biodiversity Or benefits for all, flourishing, functioning, accessible rivers and water? Aim high and it will work… It can be very much fun (and frustration!)

5. Why structures? Impound water for fishing, manage water levels, gauge flow

6. Why structures? Milling on the Loddon, impounded upstream reach Navigation on the Thames (former Harts weir)

7. Leave, remove or mitigate? Effects of weirs… • Impounding habitat and loss of functioning pool riffle/fish spawning and nursery (often dredged and poor floodplain connection) • Impact on natural processes and sediment transport • Ecology – fish, plants, invertebrates • Connectivity and migration – fish and some wildlife (net downstream drift of young which may not return) • Water quality and hazardous substances

8. What evidence for habitats failing? Reasons our ecology fails

9. Habitats before: Natural long section contains accessible habitats for all life cycle stages of ecology Riffle Pool Wood water level GRAVEL Riffle = Gravel bed with fast flowing water. Vital for invertebrates, fish spawning and plants Pool = Deep gravel or silt area with slow moving water. Vital for adult fish, invertebrates and plants

10. Habitats and fish after - effect of weir Help!!! I can`t get through Pool and riffle system lost SILT GRAVEL Anyone seen my spawning ground?

11. Habitats after - River long section: Weirs cause siltation and reduce stream power Remnant pool and riffle Lost pool and riffle Original gradient Gradient with mills \ weirs Silt

13. Kennet River habitat quality – limiting? - Fluvial audit (Geodata Institute 1999) Main river surveyed across whole catchment 4.1% ‘High sensitivity’ i.e. natural (Kennet – 0.2%) 23% ‘Low sensitivity’ (Kennet – 26%) - Aerial Fish Habitat Mapping (APEM 2007/08) 1% of Kennet (Denford-Newbury) is gravel spawning habitat 16.5% of Lambourn is gravel spawning habitat

14. Habitats: available and accessible spawning and nursery for brown trout, barbel, dace and roach? But weirs can also create wet woodland and marsh and other habitats..We look at costs and benefits…

15. Account for habitat change:Trapezoidal channel, rags brook Cross section size increased and flow variation lost >90% of river length in Thames basin modified (Driver 1996)….

16. Why fish migrate? – climate (drought, floods), spawn, compensate downstream drift, pollution, seasonal, avoid predators To complete life cycle (Lucas et al)

17. Trying to complete their life cycle – Thames salmon at Molesy But is there a future? No recruiting Thames salmon since 1832

18. Ask what the community want to see combining vision and objectives Prioritise but take opportunities Look at the options, evidence & case studies, learn what works and what does not! Do the best for what is affordable In some cases need alternative objectives (with good reasons) Cost, benefit, evaluate and feedback… What can we do about it?

19. Remove, modify or bypass barrier and add missing habitat Remove or modify damaging abstraction or attenuate upstream (wet woodland, wetlands) Modify existing fish pass Construct low-cost informal solution to assist passage Construction of formal fish pass or easement Trapping and trucking… not here I hope Some solutions – natural first..

20. Irwell weir:Remove?Restores the long sectionCan be best habitat outcome, may need tweaks

21. Kennet removal

22. Lambourn Woodspeen Mill impoundment before…

23. Lambourn at Woodspeen Mill

24. ….and after

25. Upstream Woodspeen Mill - July 07

26. Upstream Woodspeen Mill - April 2008

27. Upstream Woodspeen Mill - June 09

28. Wandle removal and replace with pool riffle

29. River Cherwell bypass

30. Bypassing weirs - Itchen navigation

31. Potential Solutions – rock ramps

32. Potential Solutions - Formal passes

33. Kennet Blakes larinier trap 1996 to 2012*2616 fish caught >99mm, 17 species

34. Loddon fish passage

35. Loddon case study:Arborfield weirs - whose problem? Water body failing for fish > 4km impounded upstream habitat Barrier to migrating fish Unsafe access Bank breaching Deteriorating wetland habitat Impact to fish spawning and nursery grounds Lack of good pre-post monitoring = opportunity for way forward balancing human and environmental needs

36. Angling Clubs: Arborleigh AC, Red Spinners, 21 Angling, Swallowfield AC, Thames Water, University of Reading, Cranfield University, Farley Estate, Loddon Fisheries and Conservation Consultative, Swallowfield Flood Resilience Committee, Barbel Society, Wokingham Borough Council, defra, APEM, Moore Consulting, Atkins, Cain Bio Engineering, Avon Construction, Environment Agency… Without whom, we’d be nowhere… I’d like to pass this on! Thank you for inspiring, helping and keeping it real…

37. Loddon 160cm weirs lowered by 70cm

38. Impacts? Loddon spawning and nursery grounds restored, wood and vegetation enhances in channel and gives cover

39. Aim high - bypass design evolution, how can we make it great but offer good value? Challenge…

40. Pool riffle pass 0-56m chainage Length 56m including inlet Gradient 1:83, 600mm WL drop 1 concrete inlet 6 staked retained weirs / riffles 1.0 m wide notches (50mm to 90mm per drop) 6 pools > 1500mm Average velocity 0.25-0.36 m s-1 Max velocity approx. 1.4 m s-1 87m long embankment (0.82 m max height)

41. Nature like bypass 56m - 200m chainage Length approx. 150 m Average gradient of the channel 1:300 V av. 0.42 m/s at Q95 and 0.65 m/s at Q20 Assumed Manning’s n = 0.075

43. Working with natural processesShift from fixed to moving parts! Woody debris for refuge and morphology adjustment Potential spawning grounds Backwaters

44. Bypass exit

45. Value added – changes in geometry, gravel ledge, backwaters

46. A difference? 7 to 11 new possible spawning habitats Reach total for 8km 11 to 16 compared to 5 or 6 before 3 backwaters DS of spawning grounds 10 pools (>500mm) 6 in the 50m technical pass, 4 in nature like pass, 300mm to 1500mm deep 1m to 11m wetted width 50 items of woody debris for refuge and scour Full of fish > 500 fish in 200m, 13 species

47. Are we achieving? 1 Communities – designing, balsam, hand digging, habitat creation, volunteer day, surveying 2 Fish passage – 13 species caught: angler targets 3 WFD fish status in the bypass probably good 4 >4km of river restored including new fish spawning 5 2 wet habitat feeds to restore >1ha + HLS plans upstream to improve connectivity 6 Provide case study?! 7 Easier site access under varying flow conditions 8 Frequency of water overtopping collapsing banks reduced and vegetation established

48. 2010 Construction, if we can’t find a digger DIY with Arborleigh Angling Club

49. “In true recognition of successfully completing the difficult and arduous task of constructing the fish pass on the River Loddon at Arborfield in July 2011” Innes Jones Area Manager “it’s the best bypass I’ve seen” Thanks to ALL those who did it! Feedback from fishing club

50. Loddon Fisheries and Conservation Consultative in practice - Team Spirit… www.lfcc.org.uk