Conservation of anabranching river system of Narew National Park

Transcription

1 Conservation of anabranching river system of Narew National Park Marcinkowski P. 1, Grabowski R. 2, Gurnell A. 3,Okruszko T. 1 1 Department of Hydraulic Engineering, Warsaw University of Life Sciences, Nowoursynowska 159, , Warsaw, Poland 2 Cranfield Water Science Institute, Cranfield University, Cranfield, Bedfordshire, UK MK40 0AP. 3 School of Geography, Queen Mary University of London, London, E1 4NS.

2 Overview Context Anastomosing systems story from the past Narew River case Management questions future expectations Conclusions

3 Context Natura 2000 Management Plans developed currently in Poland, Identification of River Basin Management Plans as a part of Water Framework Directive implementation, Number of wetland restoration projects in the frame of Life+ in Poland, REFORM (REstoring rivers FOR effective catchment Management) FP7 aimed at providing a framework for improving the success of hydromorphological restoration measures to reach, in a cost-effective manner, target ecological status or potential of rivers.

4 The story begins The first appearance of a multiple channel fluvial systems known as anabranching or anastomosing rivers, occurred during the Carboniferous period after plants development (Gutierrez 2001, Davies & Gibling 2011)

5 Classification confusion For a long time, they were frequently confused with braided rivers. Schumm (1968) may have been the first to point out that the term anastomosing should not be used as a synonym for braiding. Nowadays, the term anastomosing is reserved for a type of river with multiple, interconnected, coexisting channel belts on alluvial plains (Makaske, 2001).

6 Controlling processes Development of such system is controlled by the avulsion process which is the diversion of flow from an existing channel onto the floodplain, eventually resulting in a new channel belt (Smith and Smith, 1980; Gradziński et al. 2003). Universal conditions triggering avulsion are not described. However mutual processes across the world can be identified: the very low stream slope, occurrence of high water stage exceeding bankfull discharge for significant period of time, local flow disturbances caused by blocking structures (woods, vegetation).

7 Human interference (1) At first the system was maintained for: Fishing Timber rafting Water mills Cattle breeding..

8 Timber rafting on river Narew, (source:[wanderer] Wędrowiec, 1881) Fishing dams, (source: wikipedia) Cattle breeding (source:

9 Human interference (2) Later on it stopped being useful and was slowly destroyed by: Agricultural development; Urbanisation expansion; Extensive modifications of rivers and their floodplains; Intensive reclamation of the floodplains; Dredging of the main channel increasing its capacity to overtake redirected flow from side channels; Development of transportation; Constructing spanning structures crossing the floodplain; Large earthworks causing a major floodplain discontinuity; Flooding security structures like embankments; etc.

10 lead to: Rapid extinction of anastomosing fluvial systems Stretch of the River Warta from the past (source: Forysiak 2010) Current planform of Warta (source: google.maps)

11 Narew case Existing system (the last in Central Europe) What are the processes? Key question: should we maintain natural processes or state of the system?

12

13 Area and values Upper Narew catchment, NE part of the country. Part of the river valley protected within Narew National Park (NNP) and Natura 2000 (bird and habitat) Precious anastomosing stretches of the river, one of the last in Europe, Importance of protection: very high Case study location

14 Research questions Identify hydromorphological pressures on the River Narew within the national park; Assess their impact on the anastomosing planform to inform future management plans; Application of HF to the river system to develop a process-based understanding of hydromorphological interactions and responses; In particular, the study documents changes in the number of channels (i.e. anabranches) within the NNP over time and explores the human interventions and pressures that may have produced them.

15 Hydromorphological assessment tool Hierarchical Framework (Gurnell et al in revision) Spatial and temporal hierarchy of the assessment. Hierarchy of spatial scale units [D2.1 Multi-scale framework and indicators of hydromorphological processes and forms.]

16 Stages of analysis (brief description) 1. Spatial units delineation. Biogeographic region Catchment Landscape Units European Environment Agency Maps GIS tools, based on DEM and stream network Uniform geological, elevation and land cover conditions Reaches Segments Uniform planform and valley setting conditions Uniform river energy conditions

17 Stages of analysis (brief description) 1. Spatial units delineation. Biogeographic region (1) Catchment (1) Landscape Units (2) Reaches (35) Segments (7)

18 Findings 1 Characterisation of spatial units (in a nutshell): low stream energy (2-3 W/m 2 ), fine sand river bed substrate, dominating share of reeds and sedges in riparian corridor, very wide (2-4km) riparian corridor, steep river banks composed of organic soil, dominating morphological forms: side bars, mid-channel vegetated bars/islands, floodplain morphological forms: oxbow lakes, inactive vegetated channels, very low sediment delivery potential.

19 Stages of analysis (brief description) 2. Spatial units characterisation. 3. Detection of parameters changes in time. Biogeographic region Catchment Landscape Units No changes changes: Land use, rainfall, specific flow, water yield changes: Land use, retention (reservoir) Reaches Segments changes: duration and frequency of floods, channels extinction, riparian corridor structure changes: flow regime, flow characteristics

20 Precipitation variation Average yearly sum of precipitation ( ) from 21 gauging stations in the Narew catchment.

21 Land use The maps of land use in the basin of upper Narew river, 1,2,3,6 settlements and urbanised areas, 4- arable land, 5 pastures and meadows, 7 forests, 8,9 artificial water bodies, 10 wetland Source:(Nasiłowska 2008)

22 Reservoir operation

23

24 Important pressures Construction of Siemianówka reservoir, Cessation of mowing in NNP and expansion of common reed, Construction of bridges crossing the valley, Land reclamation in the tributaries and downstream to the park, Temporal increase of sediment delivery from industrial sources

25 Changes of the system - Local overgrowing of side channels, - Gradual extinction of dying arms. - Degradation of anastomosing system branches branches branches Overgrown side channel

26

27 Findings 2 System is out of the equilibrium; There is no single stressor the pressures are located out and in the system; The biggest observed changes somewhere in eighties.

28 Possible management options

29 Reservoir operation rules

30 Hydraulic structures Small hydraulic structures

31 Hands off on tributaries

32 Opening of the side channels Drilling places

33 Mowing

34 Findings 3 Artificial restoring might not be efficient in present valley and catchment conditions as we have not recognised the key processes yet; The best solution would be a combination of minor artificial/engineering works and (semi)natural processes.

35 Conclusions Number of ecological values present in the river valleys resulted from the extensive human activity; Conservation (restoration) activities aimed on ecological status are often against natural or social processes so we have to mimic the former system behaviour; Hierarchical analysis is an useful tool in identifying the key process in the river system; We are still looking for the tools helpful in optimising the management strategies in protected areas.

36

37 References Gutierrez M Geomorphology. Davies N.S., Gibling M.R Evolution of fixed-channel alluvial plains in response to Carboniferous vegetation. Nature Geoscience 4, Gloger Z Wanderer [Wędrowiec], Warszawa. Chętnik A, Earth [Ziemia], Warszawa. Forysiak J, The application of aerial photo analysis to reconstruct anabranching system of middle part of the Warta river valley. Landform analysis vol. 13 Schumm, S.A., Speculations concerning paleohydraulic controls on terrestrial sedimentation. Geological Society of America Bulletin 79, Smith, D.G., Smith, N.D., Sedimentation in anastomosed river systems: examples from alluvial valleys near Banff, Alberta. Journal of Sedimentary Petrology 50, Gradziński, R., Baryła, J., Doktor, M., Gmur, D., Gradziński, M., Kędzior, A., Paszkowski, M., Soja, R., Zieliński, T., Żurek, S. Vegetation-controlled modern anastomosing system of the upper Narew River (NE Poland) and its sediments. Sedimentary Geology 157(3): DOI: /S (02) A.M. Gurnell1, M. Rinaldi, B. Belletti, S. Bizzi, B. Blamauer, G. Braca, T.Buijse, M. Bussettini, B. Camenen, F. Comiti, L. Demarchi, D. García De Jalón, M. González Del Tánago, R.C. Grabowski, I.D.M. Gunn, H. Habersack, D. Hendriks, A.J. Henshaw, M. Klösch, B. Lastoria, A. Latapi, P. Marcinkowski, V. Martínez-Fernández, E. Mosselman, J.O. Mountford, L. Nardi, T. Okruszko, M.T. O Hare, M. Palma, C. Percopo, N. Surian, W. van de Bund, C. Weissteiner and L. Ziliani, A MULTI-SCALE HIERARCHICAL FRAMEWORK FOR DEVELOPING UNDERSTANDING OF RIVER BEHAVIOUR TO SUPPORT RIVER MANAGEMENT. Aquatic Sciences (in revision). Makaske, B. Anastomosing rivers: a review of their classification, origin and sedimentary products. Earth-Science Reviews Nasiłowska, S. Land use changes in the basin of upper Narew river, in XIX XX century. Teledetekcja środowiska, Warszawa, 2008.