REFORM - WP4

Fact sheets for restoration projects

tom.buijse@deltares.nl — Tue, 15 Dec 2015 19:38:48 +0000

This deliverable D4.5 summarizes information and experiences for thirteen river types and lists meta-data analysis results based on 844 publications. The report starts with a summary of a literature meta-data analysis, using the REFORM river reach typology. The main component of the report deals with fact sheets and per river type provides a synthesis of restoration experiences describing best and efficient restoration practices, including promising restoration techniques and variables suited for monitoring restoration.

Of the 22 REFORM river types, 12 types occurred in the database together with four combinations of 2-3 river types. In total, 11 pressure categories and 23 pressures were classified. Channelization was the most common pressure category in all river types. This is not surprising as the focus of the review was on hydromorphology. Second was habitat degradation followed closely by barriers/connectivity, bank degradation and flow alteration. In-channel habitat conditions are mostly improved by restoration with a broad spectrum over actual measures in this category. Next floodplain and river planform appeared mostly restored. Within the floodplain the attention went to reconnecting and creating existing backwaters, oxbow-lakes and wetlands. The river planform measures dealt with re-meandering, widening and re-braiding. The riparian zone, mainly the development of natural vegetation on buffer strips, also was often implemented. Hydrological measures were much less often executed.

The main component of the report deals with fact sheets and per river type provides a synthesis of restoration experiences describing best and efficient restoration practices, including promising restoration techniques and variables suited for monitoring restoration. The river typology that is being developed for the classification of fact sheets is based on an integration of four different classifications commonly used in Europe. Each single fact sheet consists of the paragraphs: River type name, Pressure categories/pressures, Measure categories/measures, and Monitoring scheme.

The river typology adopted for the fact sheets in this Deliverable differs from the river reach typology developed in REFORM. The relation between these typologies is not straightforward. The river typology adopted here, refers to the catchment or subcatchment setting of a river in terms of altitude, size and geology. This setting does not change in time. In contrast, the REFORM river reach typology is designed for assessing the hydromorphological functioning of individual river reaches. REFORM river reach types may change in time because they represent the response of the river reaches to processes of flow, sediment and vegetation, which can all change through time. Furthermore, river catchments or sub-catchments of a single type according to the typology used in this deliverable may contain several reaches of different REFORM types, and indeed all of the REFORM river types could potentially be found within many of the river types used in this deliverable. Notwithstanding the differences in nature, purpose and scale of these two different typologies, Table 11in the deliverable presents an indication of the range of REFORM river types that might most commonly be encountered in reaches of river located within the categories of the river typology adopted in this deliverable.

D4_5 REFORM Factsheets for restoration projects final v2.pdf

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D4.5 Fact sheets for restoration projects

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Final

Policy Brief:

Assessing the societal benefits of river restoration using the ecosystem services approach

tom.buijse@deltares.nl — Fri, 06 Mar 2015 12:43:18 +0000

The success of river restoration is often poorly quantified due to poor design, absence of proper monitoring or incomplete documentation. This study is an attempt to overcome this ex-post using the aggregating nature of the ecosystem services approach. In 8 pairs of restored reaches and their adjacent floodplains of middle-sized European rivers, we quantified as many provisioning, regulating and cultural services as possible that were of final value to humans as annual biogeochemical or –physical fluxes, or densities per year, and summed these to annual economic value normalised per area.

Methods

We separated different forms of land cover using the European harmonised land cover classification CORINE, summing per habitat type and service type. Non-market values were obtained from questionnaire surveys among inhabitants and visitors leading to a.o. willingness-to-pay estimates for restoration, water quality improvement and scenic beauty.

Results

We found a significant difference in total ecosystem service value between unrestored and restored reaches of 1400 ± 600 € ha^-1 y^-1 (2500 minus 1100, p=0.03, paired t-test and regression). We analysed possible relations with 23 physical and social geographical characteristics of the floodplain and upstream catchment after reducing these to 4 principal components explaining 80% of their variance. Cultural and regulating services correlated with human population density, cattle density and agricultural Nitrogen surplus in the catchment, but not with the fraction of arable land or forest, the slope of the floodplain or mean river discharge, or GDP. We interpret this that landscape appreciation and flood risk alleviation are a simple function of human population density. Our total ecosystem service values are comparable to recent literature values from elsewhere and scale with local annual land rent with a median ratio of 3.

Conclusions

We conclude that our approach allows ex-post evaluation of river restoration success, and posit that restoration of middle sized rivers in Europe, by and large enhances overall societal benefit.

4.4 Assessing social benefits of river restoration.pdf

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D4.4 Results of the socio-economic survey

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Report

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Final

Policy Brief:

Effects of large- and small-scale river restoration on hydromorphology and ecology

tom.buijse@deltares.nl — Wed, 10 Dec 2014 17:16:10 +0000

Summary

An increasing number of river sections have been restored in the past few decades but only a small number of these projects have been monitored. The few monitoring studies mainly investigated single organism groups, reported contrasting results, and rarely did investigate the influence of catchment, river or project characteristics. In this study, we compiled a harmonized dataset on the effects of hydromorphological river restoration measures on biota based on a standardized monitoring design to minimize scatter due to methodological differences. A broad range of response variables was recorded to draw conclusions on the effect of restoration on biota in general, including habitat composition in the river and its floodplain, three aquatic and two floodplain-inhabiting organism groups, as well as food web composition and aquatic land interactions as reflected by stable isotopes. Additional data on factors potentially constraining or enhancing the effect of restoration were compiled to identify conditions which favour restoration success. The main focus was dedicated to investigate the effect of restoration extent (as indicated by restored section length and restoration intensity).

Ten pairs of one large and a similar but small restoration project were investigated to address the role of restoration extent for river restoration effects. The restoration effect was quantified by comparing each of the 20 restored river sections to a nearby non-restored, i.e. still degraded section. The large restoration projects were representing good-practice examples in different European regions either targeting medium-sized lowland rivers or medium-sized mountain rivers. Many of the mountain rivers investigated were restored by removing bed and bank fixation, flattening river banks, and partly widening the cross-section (referred to as widening in the following). In the lowland rivers, remeandering and reconnecting oxbows were the most prominent measures besides increasing groundwater levels for restoring wetlands. Moreover, instream measures like large wood and boulder placement have been applied.

We found a significant effect on the number of ground beetle species and on richness and diversity of macrophytes, a moderate effect on fish, and a low effect on macroinvertebrates and floodplain vegetation. This isconsistent with the findings of other studies on single organism groups, except for floodplain vegetation, which usually benefits from restoration but restoration effects were constrained by agricultural land use in our study. Since the effect of restoration was generally higher on terrestrial and semi-aquatic organism groups, we recommend that they are considered in the monitoring and assessment of river restoration projects.

In general, the effect of restoration on community structure, traits, and functional indicators was more pronounced compared to the effects on species number and diversity. These changes in community structure indicate specific functional changes caused by river restoration and can be used to increase our understanding how restoration measures affect aquatic ecosystems, investigate causal relationships, and identify sustainable, (cost-) effective restoration measures. Therefore, we recommend that future restoration projects and monitoring studies should focus more on functional aspects (e.g. species traits, community structure) to investigate how river restoration affects river hydromorphology and biota, which would offer a great opportunity to make fundamental advances in restoration ecology and management.

The factors potentially constraining or enhancing the effect of restoration were partly correlated, which made it difficult to infer causal relationships (e.g. most old projects were located in gravel-bed rivers where mainly widening was the main restoration measure applied, and catchment land use was less intensive). Nevertheless, it was possible to draw some first conclusions on the conditions favouring restoration success:

It has been widely stated that large-scale pressures like water quality and fine sediment loads might constrain the effect of restoration. However, in this study, catchment land use did only affect restoration success for floodplain vegetation, and restoration effect might have been rather constrained by the limited species pool available for re-colonization and dispersal since the organism groups which did benefit most from restoration also have relatively high dispersal abilities (ground beetles, macrophytes). This topic clearly merits further investigation since a limited re-colonization potential would need a completely different restoration strategy compared to reach-scale habitat improvements.

Restoration extent (length of restored section, restoration intensity) was not the main factor determining restoration effects. Most probably, the restoration projects investigated were simply too small to benefit from possible positive effects of restoration extent, which is also supported by other recent studies. Furthermore, project age (time between implementation of the measures and monitoring) only had a positive effect on the aquatic habitat conditions but not on any of the organism groups investigated, possibly due to the young age of most projects investigated. In contrast, project age was identified as one of the most important variables affecting restoration success in the REFORM deliverable D 4.2, stressing the need to further investigate the effect of restoration over time in future studies.

Widening was applied in 11 of the projects investigated and had a significantly larger effect on hydromorphology and several organism groups (e.g. ground beetles, macrophytes) compared to other measures (among others instream measures), which is consistent with the findings of the REFORM deliverable D 4.2, and the widely endorsed assumption that restoring geomorphological processes has a higher effect compared to other measures. Since widening includes a set of measures, it was not possible to investigate the contribution of single measures. Since the positive effect on ground beetles was mainly due to the creation of open pioneer habitats covered by sparse woody vegetation, flattening river banks might already suffice but this has to be further investigated. Moreover, these results do not question the use of instream measures since transferability is limited due to the relatively low number of instream projects investigated in this study, and results of several other studies showing that instream measures generally have a positive effect on different aquatic organism groups.

The results indicated that future restoration projects should aim at increasing and monitoring habitat diversity at spatial scales which are ecologically relevant for the targeted organism groups. Although we found enhanced macro- and mesohabitats, which often is visually appealing, the measures often failed at increasing microhabitat diversity, which in turn was correlated with the effect of restoration on macroinvertebrates. Furthermore, it is not necessarily most important to increase the mere number of habitat types (e.g. habitat diversity) but to restore specific habitats which are of special importance. For ground beetles, the positive effect of widening was mainly due to the strong relationship between ground beetle richness and a specific habitat type: the open pioneer stage covered by sparse woody vegetation, but not to the mere number of habitat types.

The following more specific conclusions can be drawn for the single organism groups and river hydromorphology:

Overall, restoration increased habitat diversity through changes in channel morphology. The dominance of the main channel was significantly reduced, while other channel features such as islands, banks and bars became more frequent. The effect of restoration on hydromorphology was not higher in larger restoration projects compared to smaller projects. The effect of restoration was high for macro- and mesohabitat divsersity but low for microscale substrate composition. Key indicators for identifying restoration success should include parameters at larger spatial scales such as channel adjustments. There is a need to develop terrestrial parameters to assess the lateral dimension of restoration.

In line with other restoration studies no effects of restoration on macroinvertebrates were detected. However, macroinvertebrate richness and diversity was correlated with microhabitat diversity. While restoration projects like widening are visually appealing and increase macro- and mesohabitat diversity, they apparently rarely increase microhabitat diversity relevant for macroinvertebrates and species diversity.

Fish respond in a consistent way to hydromorphological restoration measures by an increase of rheophilic and a decrease of eurytopic fish. The restoration effect increases with habitat quality and length of restored river sections. Future restoration should focus on more dynamic, self-sustaining habitat improvements extending over several kilometres.

Restoration had an overall positive effect on richness and diversity of specific macrophytes (so-called helophytes, emergent plants rooting under water or in wetted soils) but not onemergent and submerged aquatic plants(hydrophytes). Restoration effects were especially high in widening projects located in mountain rivers.

An increase in total ground beetles species richness and richness of habitat specialists could be achieved primarily by creating pioneer patches, for example by river widening, which result in more open banks. Suitable restoration measures should aim on a strong lateral connection between the river and its floodplain. Further research should focus on determining optimal conditions of such pioneer habitats.

Responses of floodplain vegetation were related to changes in trait composition, while general effects on diversity were limited (small restoration projects) or absent (large restoration projects). Few general responses to restoration could be detected because species and trait composition and plant diversity varied substantially between the European regions.

For stable isotopes results supported our hypotheses that trophic length (indicated by Δ15N) as well as diversity of assimilated food sources (indicated by Δ13C) increase with restoration. Δ13C was significantly larger in large restoration projects compared to the corresponding degraded sections, suggesting that macroinvertebrates were feeding from more diverse sources. The results underlined the necessity to limit comparisons to sections within a region, as large-scale differences possibly masked the effects of restoration.

4.3 Effects of large- and small-scale restoration.pdf

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D4.3 Results of the hydromorphological and ecological survey

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Report

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Final

Policy Brief:

Field protocols and associated database for paired river restoration comparison

tom.buijse@deltares.nl — Fri, 15 Aug 2014 09:22:12 +0000

WP4 evaluates effects of river restoration by analysing existing data as well as performing field studies on paired catchments. In tasks 4.2 and 4.3 field studies will use examples of restored sites in which either one large scale measure (flagship restoration site) or smaller restoration measures (small restoration site) have been implemented. These restoration sites will be compared to “control sites” that are situated upstream and are still degraded (nested design). All case study sites comprise mid-sized mountain rivers or mid-sized lowland rivers throughout Europe. D4.1 includes sampling manuals, field forms and protocols for all these abiotic and biotic parameters to ensure comparable datasets for all case study sites.

For all case study sites we collect environmental data, biotic and functional parameters potentially supporting or spoiling restoration success. The data collection encompasses Site information, Hydromorphology, Pressure types, Restoration measure types, Physico-chemical data; Fish, Invertebrates, Macrophytes, Riparian arthropods and Floodplain Vegetation.

4.1 Field protocols and associated database_final.pdf

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D4.1 Field protocols and associated database

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Report

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Policy Brief:

Evaluation of hydromorphological restoration from existing data

tom.buijse@deltares.nl — Fri, 15 Aug 2014 08:15:59 +0000

An increasing number of rivers have been restored over the past few decades but only a small number of these projects have been monitored, and hence, the knowledge on the effect of river restoration on biota is limited. Nevertheless, monitoring results of several projects are available in peer-reviewed scientific literature and have been compiled in recent research projects. The objective was to evaluate the effect of hydromorphological restoration on biota based on these existing data. Specific objectives were to quantify restoration success, to identify catchment, river reach, and project characteristics which influence (either constrain or enhance) the effect of restoration, and to derive recommendations for river management. The study is complemented by a satellite topic on urban river restoration.

Some narrative reviews have already been published, but a comprehensive quantitative meta-analysis which summarizes the findings of these existing studies was lacking. In the meta-analysis, quantitative research findings from a large number of studies were compiled. A meta-analysis is restricted to one single type of research finding and qualitative information cannot be used, but it is less subjective than narrative reviews and allows to investigate the effect of “moderator variables”, i.e. to identify variables which influence restoration success and hence, to identify effective measures and to describe favourable conditions for river restoration. The meta-analysis was complemented by a satellite topic on urban restoration to identify differences between the characteristics of urban and non-urban restoration projects.

Based on the results of the meta-analysis, the satellite topic, and other comprehensive reviews on river restoration already published in literature, the following conclusions were drawn. It is important to note that - as for all statistical analysis - it is not possible to infer causal relationships and hence, results should be interpreted with caution. Furthermore, for most results of this study, restoration success refers to an increase in the number of individuals and taxa simply because these metrics were reported in literature, but other metrics might be better suited to quantify success (e.g. stream-type specific conditions, functional approaches). It is strongly recommended to read the results and discussion sections before applying the results to avoid oversimplified interpretations.

In summary, it was possible to draw some first conclusion for river management from the evaluation of hydromorphological restoration based on existing monitoring data. However, monitoring data are still scarce and more robust, practical relevant, and quantitative results (e.g. thresholds) could be derived and river management would benefit from (i) original monitoring data, which would allow to use functional metrics to investigate the underlying processes and to infer causal relationships, (ii) full before-after-control-impact monitoring designs, which most probably would substantially decrease scatter in the datasets and analyses, (iii) a larger number of monitored projects, which easily could be accomplished since a large number of hydromorphological restoration measures will be implemented in the upcoming years, (iv) the availability of long-time monitoring data sets to investigate the effect of project age,which was identified as the most important variable affecting restoration success. A more intensive exchange and collaboration between river science and river management in planning monitoring programs is strongly recommended. This would offer a great opportunity to make fundamental advances in our understanding of how river restoration affects river hydromorphology and biota and to identify (cost)-effective restoration measures.

Overall, the effect of hydromorphological restoration on biota is positive but variability is high: Restoration in general has a positive effect on floodplain vegetation, ground beetles, macrophytes, fish, and invertebrates. Since variability is high, adaptive management approaches are recommended.

Restoration effect differs between organism groups:It cannot be expected that all organism groups benefit from restoration to the same extent. Results indicate that, in general, restoration effect on diversity is highest for terrestrial and semi-aquatic groups like floodplain vegetation and ground beetles, intermediate for macrophytes, lower for fish, and lowest for macroinvertebrates.

Restoration has a higher effect on the number of individuals than on the number of taxa:The effect of restoration is more pronounced on the number of fish and invertebrate individuals than on the number of taxa.

Restoration effect does only slightly differ between measures, i.e. there is no single “best” measure:There are no large differences in the overall effect of different measures but there is a tendency that terrestrial and semi-aquatic organism groups like floodplain vegetation and ground beetles as well as macrophytes benefit most from channel-planform measures and aquatic groups like fish and invertebrates from instream measures.

Urban restoration projects do not substantially differ in respect to the pressures occurring and the measures applied: Urban restoration projects were mainly applied in small rivers and length of the restored reaches was shorter compared to non-urban restoration projects. However, approaches towards (sub)urban and non-urban river rehabilitation practices were similar.

Urban restoration projects are rated less successful compared to non-urban projects by scientists and river managers: …which is probably due to the low absolute effect, which is rated as a failure, but which often is a high relative effect since urban river start from a low base, and hence, should not be assessed too negative.

Conditions which favour restoration success can be identified but restoration outcome cannot be predicted: Restoration success is especially high for the different organism groups under specific conditions (see section 2.2.5) but the variance explained by the models is too low and low sample size restricted the use of rigorous statistical tests to really predict the restoration outcome.

Overall, restoration success most strongly depends on project age, river width, and is affected by agricultural land use:Success is generally lower but restoration still has a positive effect in catchments dominated by agricultural land use. Since land use is a proxy for e.g. water quality, there is an urgent need to identify the underlying causal relationships.Project age is the most important predictor affecting restoration success, but the direction of the effect of project age on restoration success differs between organism groups (no simple increase of effect with time). There is an urgent need for long-time monitoring to investigate the restoration effect over time, to better understand the trajectories of change induced by restoration measures, and to identify sustainable measures which enhance biota in the long-term.

4.2 Evaluating HyMo restoration from existing data FINAL.pdf

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D4.2 Evaluation of hydromorphological restoration from existing data

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Report

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Final

Policy Brief:

D4.1 Field protocols and associated database

tom.buijse@deltares.nl — Fri, 10 Aug 2012 15:39:08 +0000

WP4 evaluates effects of river restoration by analysing existing data as well as performing field studies on paired catchments. The field studies will use examples of restored sites in which either one large scale measure (flagship restoration site) or smaller restoration measures (small restoration site) have been implemented. These restoration sites will be compared to “control sites” that are situated upstream and are still degraded (nested design). Deliverable 4.1. documents the abiotic and biotic parameters to be recorded at the case study sites and provides a description of the methods for field investigations in 2012 and 2013 including manuals, field forms and protocols.

For all case study sites we collect environmental data, biotic and functional parameters potentially supporting or spoiling restoration success. To manage the gathered data, a database was created in two steps. To collect the data from all case study partners a Microsoft Excel file with 33 sheets was created at first. In this file 10 key subjects are required - 5 abiotic and 5 biotic topics (Site information, Hydromorphology, Pressure types, Restoration measure types, Physico-chemical data; Fish, Invertebrates, Macrophytes, Riparian arthropods, Floodplain Vegetation). Secondly, the received datasets will be merged in a Microsoft Access database. Additionally the procedure of the selection and final determination of the parameters and field methods are described as well as the general sampling design and techniques. The site-specific record sets will be complemented by data at catchment scale.

To manage the gathered data, a database was created. The final section of this report provides an overview of the structure and organisation of the database and a compilation of tables showing the set of variables to be recorded and their detailed description.

Data on river hydromorphology (CEN compliant survey method and meso/microhabitat transect method) and functional parameter (stable isotope analyses) will be recorded during the first year. Methods have been discussed during the REFORM workshop at Florence in December 2011 and at the field training workshop at Silkeborg in May 2012.

The biotic parameters will be checked if available datasets are comparable and useful for data analyses. Biotic core parameters are fish, macroinvertebrates, macrophytes, riparian arthropods and floodplain vegetation.

D4.1. includes sampling manuals, field forms and protocols for all these abiotic and biotic parameters to ensure comparable datasets for all case study sites.