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Floodplain Biodiversity and Restoration: Integrated natural science and socio-economic approaches to catchment management

Programme “Energy, Environment and Sustainable Development”
Call Identifier: EESD-ENV-99-1 (JO 1999/C 77/12)
Proposal No. EVK1-1999-00154
Second Meeting
Clermont Ferrand
23-25 February 2001

Present:

Photograph of those present

From left to right: Standing – Rachel Horn (C), Jochen Monstadt (B), Hélène Guilloy (T), Franck Vautier (G), Thomas Weith (B), Phillippe Belleudy (G), Marie-Françoise André (Cl), Stephane Petit (Cl), Etienne Muller (T), Francine Hughes (C), Christer Nilsson (U), Shaojung Xiong (U), Luc Lambs (T), Tim Moss (B), Catharine Allain (G); Crouching – Adrian Hayes (C), Nadia Barsoum (C), Jean-Luc Peiry (Cl), Jacky Girel (G), Matts Johannesson (U). Photograph taken by Keith Richards (C). (Key: G = Grenoble, C = Cambridge, L = Lethbridge, B = Berlin, U = Umeå, T = Toulouse, Cl = Clermont)

Welcome and introduction (Keith Richards)

Keith began by welcoming everyone on Friday morning (23 February), and outlining the aims and structure of the Meeting. The aims were to summarise the procedures for completing the first Annual Report; and to make progress with Work Packages 1 and 7 while the whole group was together.

Francine noted that the Annual Report required an equivalent of the form of Management Report produced at the 6-month stage, a two page summary report, plus a lengthier summary of progress by Work Package (up to four pages for each). In addition she reminded everyone that draft Technology Implementation Plans are also needed at this stage. Keith suggested that the meetings of Work Package groups timed for the Friday afternoon could therefore select a rapporteur for the plenary meeting on Saturday morning, when a summary could be presented that would in essence form the basis for the Work Package report.

However, the first part of the Meeting would be devoted to a presentation by the Berlin group of their progress with the institutional analysis for Work Package 7, followed by parallel Workshop sessions led by the three members of the group. Thomas would meet the Flobar members from England and Wales to discuss the interpretation of the institutional stuctures in these countries, while Jochen would meet the French members and Tim the Swedish members.

Work Package 7: Overview (Tim Moss, Jochen Monstadt, Thomas Weith)

Tim began by outlining the three “activities” of this Work Package. The first was a review of the institutions for water management (organisations, laws, policies, instruments, regulations, and public/private/voluntary sector bodies, in England and Wales, France, Germany, and Sweden. The second was a more specific assessment of institutions for floodplain restoration; and the third was a series of case studies. The first phase involved preparation of a structured diagrammatic representation of the institutions (international, national, regional and local) for each country; then an analysis of strengths and weaknesses on several criteria. These included political credibility, level of co-ordination, processes, participation, effectiveness, economic efficiency and innovation.

Tim, Jochen and Thomas then presented the draft results of Activity 1 (the diagrams) for the four countries. Members were immediately struck by the way the differences emerged in this representation; Sweden a relatively simple structure, France a centralised top-down stucture, Germany a strongly regional structure, and the UK a complex web of institutions.

Tim emphasised that the diagrams were to be taken as drafts at this stage, and that they should not be disseminated outside the Flobar group yet. It was noted that progress with Activity 2 was for the future; and that it would require consideration of links between water management and land use management institutions. It was also noted that criteria for the selection of case studies had been considered, and included the existence of reasonable institutional complexity, scale of project, success in implementation etc. These criteria would be considered in the Workshop sessions.

Work Package 7: Workshop Sessions.

The Work Package 7 team led discussions with groups of other members; Thomas with those from England and Wales, Jochen with those from France, and Tim with those from Sweden. These Workshops discussed the details of the diagrams, the interpretations of institutional inter-relationships and functions, the strengths and weaknesses as they were perceived by the national groups, and the criteria for selecting case studies.

Work Packages 1-6.

Separate meetings were held of the partners involved in the remaining Work Packages, with a view to discussing progress and future intended research, and with the objective of providing summaries for the plenary session on Saturday morning, at which the Work Package convenors would act as rapporteurs. The following sections summarise these reports on Work Package discussions.

Work Package 1 (Francine Hughes).

The objective of Work Package 1 is to develop a manual of scientific guidelines on best practices for water allocation specifically to improve the quality of floodplain woodland ecosystems. Francine outlined the aims of the Work Package, drawing parallels with the single function and multi-function methods already developed for restoration of aquatic ecosystems – the recruitment box method, and the building block method being approximate equivalents of PHABSIM and Catchment Abstraction Management Plans. She also reviewed the productive discussions held with the Stakeholder Committee established in the UK to advise on the appropriate form of the proposed Manual of Guidelines for Floodplain woodland Restoration. She noted that the Committee was widely supportive of the view that there was considerable potential for floodplain woodland restoration following the winter flooding in the UK, with a window of opportunity opening for proposals for flood retention on wooded floodplain areas in order to reduce flooding downstream.

The Committee had suggested producing a Manual in two stages: a 10-page executive summary for policy groups/individuals, and a 50-page technical annexe. Francine outlined a preliminary table of contents for the manual and explained that following the discussions held at the annual meeting she would send it to all FLOBAR2 members for comment. It is anticipated that subsections of the manual will be written by different members of FLOBAR2.

Work Package 2 (Luc Lambs).

The objective of Work Package 2 is to investigate the links between hydrological inputs to floodplains and the consumption of water and growth by woody riparian species. Luc outlined the progress of his and Gerard’s work towards this objective. This review included his own studies of the temperature, electrical conductivity, stable isotope characteristics, and soil moisture and groundwater status at sites on the Garonne River. He illustrated these studies with the extensive data sets already accumulated at these sites.

The work undertaken at Grenoble by Gerard Marigo (who had been unable to attend the Meeting) focused on plant physiological responses to drought, with particular reference to the regulation by the plant of its stomatal resistance to reduce water use, and the increase of hydraulic resistivity. This work has been variously concerned with Alnus, Quercus, Populus and Fraxinus species.

Some useful discussion noted the question of upscaling from single trees to areal assessment of water needs of riparian woodland; Luc noted that this might be problematic because individual trees of the same species behave differently, but that an idea might be obtained from the poplar plantations along the Garonne.

Work Package 3 (Mats Johansson and Shaojun Xiong).

The objective of Work Package 3 is to investigate plant community response to manipulated changes in hydrology and litter dynamics, with particular reference to their impacts on biodiversity. Mats outlined a well-planned factorial experiment on the Vindel River in northern Sweden designed to investigate the interaction of hydrology and water level on biomass production and species coexistence. This has involved 96 plots in which 72 required excavation of near-undisturbed soil turves (a fairly physical experiment!). Each “plot” is in fact a multiple plot with areas for recording species composition, and for sampling biomass.

The experiment is ongoing, but after the first season, plots from the highest level lost species when moved to the lowest level, where naturally there is a lower species richness but a higher biomass (giving rise to a frequently noted inverse relationship between biomass and species richness).

Following this presentation, Shaojun described a second experiment in which a similar experiment on the interaction of hydrology and litter will be performed in a small channel near Wicken Fen. In this experiment locally collected seeds will be sown in plots at different heights with cleared and uncleared leaf litter, with the plots being monitored for germination and subsequent growth. The seeds have been collected and preserved, and the experiment is expected to begin in the spring. Greenhouse germination experiments will also be performed to add a more controlled test of this phase of the experiment.

Work Package 4 (Mats Johansson).

The Objective of Workpackage 4 is to investigate the influence of hydrology and other environmental variables on the sex ratios found on floodplains among members of the dioecious Salicaceae family. Mats reported on experimental observations designed to assess whether sex ratios of dioecious species vary along a hydrological gradient, and whether they vary between free-flowing and controlled river reaches.

The first question was tested in three areas of the Vindel River, using Salix spp. The results showed that female trees were consistently more common, but that no spatial separation of the sexes occurred with height above river level. It is however unclear if the observed predominance of females in the study sites differs from the overall biased sex ratio towards females in the region which is due to differential effects of herbivory. A similar result was found in an examination of sex ratio differences between rivers – females were again more common, but the sex ratio did not vary between managed and free-flowing rivers.

It was planned to investigate this issue further with additional field studies, and possibly with greenhouse experiments using Salix spp.

Work Package 5 (Mark Winfield and Nadia Barsoum).

The objective of Work Package 5 is to investigate the influence of hydrological and sedimentological inputs to floodplains on the proportions of vegetative and non-vegetative regeneration exhibited by the early successional members of the genus Populus. Nadia reported an experimental design for the River Drome, where seedling counts had been made along cross-section lines in both the channelised and the freely-migrating reach, and a GIS/Remote Sensing study was currently under way to investigate patches and measure their stability in relation to rates of colonisation and sediment turnover. The ultimate aim of this study was to examine the relative roles of vegetative and seed-based regeneration in controlled and uncontrolled river reaches (and therefore the genetic diversity associated with different river behaviours).

Mark then explained how the genetic analysis of plant tissue progressed, and how it related to the sampling design. Plant tissue samples had been obtained from vegetated areas of the two reaches of the Drome, along the edges and in the centre of vegetated bars. Samples were not collected from shoots that actually appeared to have been produced vegetatively (for example, on bank edges where it was clear that shoots were from common root stock). The cluster analysis of lines in the DNA traces suggested that samples from both channelised and freely migrating reaches, and from the edge and centre of patches, all have high levels of similarity (of the order of 88%), but that this level was nevertheless less than would be expected from clones. There is as much diversity at one site on an island as there is on the island as a whole (that is, not much diversity), but there is nevertheless not much evidence of clonality although there is visible evidence of vegetative reproduction.

Work Package 6 (Keith Richards).

The objective of Work Package 6 is to investigate the flow resistance associated with riparian vegetation. Keith reported that three research students were now working on this Work Package (Catharine Allain at Grenoble, Rachel Horn in Cambridge, and Stephane Petit in Clermont). Research was well under way across a broad front. Flume experiments would identify the roughness of stems of varying densities, with different arrangements and different surface roughnesses; and attempts would be made to model the ground level flora of herbs and bushes on a two-level velocity profile with a slow-flow region in the ground-level vegetation, and a fast-flow region above. The Cambridge group had designed a method to enable collection of field data on overbank flow velocities through floodplain woodland, using a tracer study. Field investigations carried out by the Grenoble group included the mapping of flow directions in overbank flow events over the Brignoud Island, and the surveying of the water surface slope over a 15km reach of the Isère in order to analyse the total head loss over this reach. Field mapping of vegetation types and densities provided an essential empirical requirement for estimation of the flow resistance, and significant progress had been made in mapping vegetation along an 80km reach of the Isère from Albertville to Grenoble.

Three approaches to the numerical modelling of flow properties had been attempted to date, including (i) a 1D model to simulate global head loss over the 15km reach of the Isère from Grenoble to the Brignoud Island; (ii) a 2D model to simulate the pattern of flow direction and velocity across the Brignoud Island during a flood inundation; and (iii) a 2D model to study spatial patterns of velocity and shear stress in the Isère River around bars and islands, as a basis for interpreting and predicting the locations and rates of deposition and erosion.

Studies had been initiated on the patterns and rates of sedimentation within woody vegetation areas on the floodplains of the Isère and the Allier. On the Isère at Brignoud, a longer-term study of sedimentation has been sustained following two floods in October 2000, which deposited fine sediment 40cm thick. On the Allier, a 300m wide floodplain is extensively inundated during floods, and here the aim is to examine distribution of sedimentation at two scales. Modelling of sediment transport is also being undertaken. A 2D model of the velocity profile is being used to investigate suspended sediment advection through the upper fast-flow region, and the trapping and deposition of suspended sediment in the lower slow-flow region amongst the ground vegetation. In addition, a 2D model is being used to simulate bedload transport patterns, bank erosion, and island destruction.

Close watch is being kept on the implications of their research for river management. This is reflected in the work by Frank and Jacky on the different strategies for management of bar/island vegetation in the 80km stretch of the Isère from Albertville to Grenoble. The management practice of cutting vegetation and scraping surface sediment and roots has been shown to be beneficial for both flood control and biodiversity. PB and J-LP organised a successful Workshop in Lyon on 9 November 2000, attended by 82 individuals roughly divided into three equal groups of scientists, river managers and engineers, and entitled: Interactions entre l’évolution des cours d’eau et la végétation.

Conclusion (Keith Richards).

To conclude the formal elements of the Meeting, Keith reminded team members of the requirements for reporting at the end of the First Year, and the dates for provision of scientific and financial information to Francine.

He then concluded by thanking Jean-Luc and Marie-Françoise for creating an environment conducive to such an excellent and productive meeting.

Field excursion (Jean-Luc Peiry).

The team departed after lunch on saturday for a field trip to sites on the Allier River north of Clermont, which were to be the locations of field study for Work Package 6.