DSD-INT 2017 Biogeomorphodynamics of rivers, estuaries and their floodplains - Kleinhans
•
1 j'aime•2,046 vues
Presentation by Maarten Kleinhans, University of Utrecht, Netherlands, at the Delft3D - User Days (Day 2: Sediment transport and morphology), during Delft Software Days - Edition 2017. Tuesday, 31 October 2017, Delft.
Recommandé
Recommandé
Contenu connexe
Tendances
Tendances (20)
Similaire à DSD-INT 2017 Biogeomorphodynamics of rivers, estuaries and their floodplains - Kleinhans
Similaire à DSD-INT 2017 Biogeomorphodynamics of rivers, estuaries and their floodplains - Kleinhans (20)
Plus de Deltares
Plus de Deltares (20)
Dernier
Dernier (20)
DSD-INT 2017 Biogeomorphodynamics of rivers, estuaries and their floodplains - Kleinhans
- 1. Faculty of Geosciences River and delta morphodynamics Biogeomorphodynamics of rivers, estuaries and their floodplains Maarten G. Kleinhans L. Braat, I. Lokhorst, B. de Vries, M. van Oorschot, S. Selakovic, M. Brückner
- 2. To twist the lion’s tail Kleinhans et al. 2010 HESS reality conceptual model, description numerical model experiment
- 3. 3
- 4. 4 Uniformly seeded vs spread by water van Dijk et al. 2014 WRR
- 5. Size of a river? discharge sets the size (hydraulic geometry) bank stability modifies width/depth threshold channel (Parker) → braiding vegetated and muddy floodplains (our experiments + models) → meandering Eco-engineering species: mainly vegetation Spread by water 5
- 6. Model of a numerical model time- dependent boundary conditions f (t) flow, waves sand and mud transport morphology, sedimentology Delft3D ▪ hydrodynamics ▪ flow resistance ▪ bioturbation/ stabilisation ▪ substrate ▪ peat formation settling growth mortality select species habitats Life stages: engineering traits van Oorschot et al. 2016 Eco-engineers 6
- 7. 7 6 August 2013: 46 m3/s
- 8. 8 9 August 2013: 326 m3/s (max: 800)
- 10. The life and death of willow and poplar 10 Flooding (days) Dessication (days) Flow velocity (m/s) Mortality (%) Sensitive Resistant Burial : sedimentation > shoot height Scour: erosion > rooting depth van Oorschot et al. 2016 ESPL
- 11. 300 years 3 bends 3.7 km variable Q,H: 11 50-400 m3/s, 2-4 m depth Idealised model inspired by Allier river vegetationdepth (m) van Oorschot et al. 2016 ESPL
- 12. Oxbows Chute cut-off Age distribution Chute cut-off Age distribution Oxbows River morphology observed Bed levelSeedlings Saplings Forest River morphology modelled Comparison
- 13. 13 Mud + vegetation Only mud Mud only less high water less dynamic Vegetation mud along channel more confined and more dynamic vegetation mud mud depth Bente de Vries MSc thesis
- 14. 14 meanfractiononthesurface distance from channel (m) Levees encroach when vegetated Bente de Vries MSc thesis
- 15. Rivers with vegetation + mud More vegetation causes higher flood levels: Combination mud+vegetation: mud well-spread over floodplain close to channel due to vegetation on levees Our numerical model is now muddy, alive and kicking 15
- 16. Dovey estuary (Wales) initial conditions biomorphological processes boundary condition 16
- 17. Vegetation in estuaries: triple trouble? bank stabilised Not a threshold channel Salt marsh and mud flats form protective vegetated and muddy ‘floodplains’? Width/depth modified Bar patterns? Deepening and funneling, or reduction of intertidal area? Tides penetrate further? Longer estuary?? Filling of intertidal leads to flood-dominance? 17 Braat et al. 2017 ESurf de Haas et al. 2017 accepted ESR
- 18. Osborne Reynolds 1842-1912 Scaling well-done*, results nearly useless * from engineering perspective 18
- 19. 19
- 20. www.uu.nl/metronome 20 River: - flow - walnut - seeds Sea: - constant H - waves Scaling: 1:1000 space/time Sediment mobility 1:1
- 21. 21 we go nuts for mud Braat et al. in prep.
- 22. 22 tidal storage filled: ebb-flow reduced → infilling focused channel reduces self-formed friction and lowers water levels → confinement
- 23. Salt marsh 1:1000 23 mm Veronica beccabunga Lokhorst et al. in prep. ESPL
- 25. 25 funneling funneling transitioning to marsh / floodplain transitioning to marsh / floodplain
- 26. 26 Clean sand Vegetation Mud Vegetation and mud Wanna see this pic? Register: www.uu.nl/bruningslecture
- 27. Size of an estuary? Bars scale with estuary width Mud confines width and reduces tidal prism → flood dominance Vegetation enhances mud accretion and focusses flow 27
- 28. Mud funnels and fixes 28 Concentration in river 50 mg/L 20 mg/L 5 mg/L 0 mg/L mud at surfacebed level Braat et al. Esurf 2017 Delft3D
- 29. First attempts with mud + vegetation More funneling and fixing, but also filling? Issues: hydrodynamic and morphological timestep ecological timestep: integrating past conditions bank erosion waves: computational time 29 Braat Lokhorst Brückner
- 30. Vegetation on tidal bar, Westerschelde 30 Muriel Brückner in prep
- 31. Outlook: species data-model 31 Selakovic et al. in prep. ESPL
- 32. Outlook: Holocene estuaries 32 de Haas et al. in prep. Sedimentology peat levees
- 33. 33 Geomorphologists Geologists dynamic equilibrium filling up constant / changing boundary conditions forcings attempt modelling centuries know about millenial scale study living landscapes study dead landscapes cross cultural divide + collaborate
- 34. Conclusions Dynamic river meandering and estuary shape+evolution: requires living landscapes Species Settling, growth, mortality as function of hydromorphodynamics (Mijke van Oorschot, presentation tomorrow) Eco-engineering effects on hydromorphodynamics incl. mud 34
- 35. 35
- 36. Three methods Landscape experiments Numerical model Field observations samples remote sensing geology 36 Rivers and estuaries with mud and vegetation
- 37. 37 No mud 0-15 (mm) 1 m 20% ‘mud’ supply Van Dijk, van de Lageweg & Kleinhans 2013 ESPL Our river experiments: effect of mud
- 38. 38 van Dijk et al. 2014 WRR
- 39. 39 Allier river, France valley confinement + hydraulic resistance of vegetation = higher flood water levels More overbank flow!
- 40. Dynamic biomorph, so much young veg 40Harke Douma & Elisabeth Addink (in prep.) low vegetation pioneerstree cover
- 41. 41 vegetation + mud vegetation mud nothing Bente de Vries MSc thesis
- 42. 42 Kleinhans et al. in prep ESPL
- 43. Endmembers in shape? 43 Andre Ermolaev Mahakam Google Earth < threshold channel versus stable banks > tidal wave dampens tidal wave funnels
- 44. Experiments: tilting flume for tidal flows nature 20 m rivers analogue model 2 cm estuaries old method flood ebb flood ebb steeper won’t work: low flood mobility tidal wave decays ebb flood new method periodic tiltneed same mobility has same sand → steeper Kleinhans et al. 2014 ESR Kleinhans et al. 2015 JGR, 2017 Esurf accepted 44
- 45. Clean sand With mud Braat et al. in prep.