Floodplain Restoration Projects Research Articles

A Comprehensive Report of Activities and Monitoring Conducted in the Azame-no-se Floodplain Restoration Project

A Comprehensive Report of Activities and Monitoring Conducted in the Azame-no-se Floodplain Restoration Project

Dynamic floodplain vegetation model development for the Kootenai River, USA

The Kootenai River floodplain in Idaho, USA, is nearly disconnected from its main channel due to levee construction and the operation of Libby Dam since 1972. The decreases in flood frequency and magnitude combined with the river modification have changed the physical processes and the dynamics of floodplain vegetation. This research describes the concept, methodologies and simulated results of the rule-based dynamic floodplain vegetation model "CASiMiR-vegetation" that is used to simulate the effect of hydrological alteration on vegetation dynamics. The vegetation dynamics are simulated based on existing theory but adapted to observed field data on the Kootenai River. The model simulates the changing vegetation patterns on an annual basis from an initial condition based on spatially distributed physical parameters such as shear stress, flood duration and height-over-base flow level. The model was calibrated and the robustness of the model was analyzed. The hydrodynamic (HD) models were used to simulate relevant physical processes representing historic, pre-dam, and post-dam conditions from different representative hydrographs. The general concept of the vegetation model is that a vegetation community will be recycled if the magnitude of a relevant physical parameter is greater than the threshold value for specific vegetation; otherwise, succession will take place toward maturation stage. The overall accuracy and agreement Kappa between simulated and field observed maps were low considering individual vegetation types in both calibration and validation areas. Overall accuracy (42% and 58%) and agreement between maps (0.18 and 0.27) increased notably when individual vegetation types were merged into vegetation phases in both calibration and validation areas, respectively. The area balance approach was used to analyze the proportion of area occupied by different vegetation phases in the simulated and observed map. The result showed the impact of the river modification and hydrological alteration on the floodplain vegetation. The spatially distributed vegetation model developed in this study is a step forward in modeling riparian vegetation succession and can be used for operational loss assessment, and river and floodplain restoration projects.

A study of seed dispersal by flood flow in an artificially restored floodplain

Riverine floodplains play many important roles in river ecosystems. However, many floodplains have suffered degradation or loss of ecological function due to excessive river improvements or through changes in agricultural systems. As a result, many floodplain restoration projects are being conducted worldwide. One of the many methods being implemented to restore floodplain vegetation is flood water seed dispersal. In this technique, precisely estimating the effect of seed dispersal by flood water is important in order to achieve successful floodplain revegetation. Here, we focus our attention on sediment transport by flood water into the Azamenose Swamp, a restored floodplain. We attempt to estimate the function of seed deposition in the restored floodplain and explain how the seeds are deposited in the floodplain by flood water. The result suggests that the restored floodplain functions as a more appropriate deposition site for seeds than the riverbanks of the main river. It was also found that the distance from the inflow site and the weight of the sediment were related to seed deposition.

Local residents’ perceptions of floodplain restoration measures in Luxembourg's Syr Valley

The need for the restoration of semi-natural floodplain-river systems in Europe is widely recognised, and is currently a major task facing those responsible for conservation policy and water management. However, the long-term success of restoration measures and subsequent floodplain management depends largely on their cultural sustainability, which is related to perceptions of the resultant land use changes. In this study, residents of three communities adjacent to a floodplain restoration project in the Syr Valley (Luxembourg) were surveyed on their perception of the threat to floodplains, and their attitudes towards the restoration measures applied. The restoration involved the relocation of the River Syr into the valley bottom and the installation of a low-intensity grazing system. Although local residents did not perceive the floodplains of Luxembourg to be threatened on the whole, a large majority wanted to see more natural and healthy floodplain ecosystems and sought the implementation of eco-agricultural practices in future floodplain landscapes. Support for river restoration and low-intensity grazing was high, and support for their specific implementation to restore the Syr floodplain even greater. The direction of opinions could be predicted on the basis of basic beliefs, lifestyle concept and environmental behaviour, whereas socio-demographic variables were only of minor importance. These results suggested that the mimicking of past floodplain landscapes was viewed positively by the public, but to guarantee its long-term cultural sustainability landscape planners should direct their information and participation efforts actively towards different lifestyle groups.

Genetic Stock Composition of Subyearling Chinook Salmon in Seasonal Floodplain Wetlands of the Lower Willamette River, Oregon

AbstractWe used genetic identification methods to examine the stock composition of subyearling Chinook salmon Oncorhynchus tshawytscha in floodplain wetland and main‐stem habitats of the lower Willamette River, Oregon. Using a microsatellite DNA baseline of 13 standardized loci and 30 Columbia River basin populations, we analyzed 280 subyearlings collected in winter and spring 2005‐2006 from wetland and main‐stem river sites. Genetic stock identification analysis indicated that spring Chinook salmon originating from the Willamette River made up a substantial proportion of the samples and contributed 16‐71% to sample mixtures representing the wetland habitat sites. Fall Chinook salmon from lower Columbia River sources were also present and contributed 58% of winter samples. Spring Chinook salmon from lower Columbia River populations were present in both wetland (17%) and river (16%) samples in spring 2005, and subyearlings from summer‐fall‐run populations in the middle and upper Columbia River contributed to spring wetland samples in 2006 (26%). The results suggest that floodplain restoration projects intended to improve fish habitats during winter and spring periods in the lower Willamette River may benefit Chinook salmon populations from the upper Willamette River, lower Columbia River, and upper Columbia River summer‐fall evolutionarily significant units.

Management approaches to floodplain restoration and stakeholder engagement in the UK: a survey

This paper reviews selected floodplain restoration projects in the UK that have generated data for flood peak reduction and/or, water quality benefits and ecological improvement. The objective was to examine their effectiveness, both in terms of environmental improvement and the decision making of the planning and stakeholder groups that led to their implementation. For riparian zone reforestation, modelling shows that benefits from flood risk reduction are obtained at large scales due mainly to increases in floodplain surface roughness. However, little conclusive proof has been uncovered for benefits, solely in terms of flood risk reduction, on smaller scales. Alternative benefits such as diffuse pollution reduction, with benefits for ecological status targets, often provide better rationales at such scales. Success is realised when the multiple benefits of restoration programmes are clearly communicated and key stakeholders and landowners involved from the planning stage.

Nesting Success of Acadian Flycatchers (Empidonax Virescens) in Floodplain Forest Corridors

AbstractReconnecting forest patches, including those of floodplain forest, often involves the creation of long, narrow corridors that have the potential to act as ecological traps for wildlife. We examined the effect of forest width and habitat composition of the landscapes immediately around nest patches on survival and parasitism of 359 Acadian Flycatcher (Empidonax virescens) nests in the Cache River Bioreserve in southern Illinois. Nests were distributed among 19 floodplain forest corridors along a small river system that is being restored and reconnected along its original floodplain. The corridors spanned a range of widths (80–3,170 m) and varied with the presence or absence of natural water-related habitats (beaver ponds, backwater swamps, and creeks). Although nest success varied slightly between stages of the breeding cycle, confidence intervals overlapped, which suggests constant nest success throughout the breeding cycle. Nest survival was relatively high by regional standards but did not vary significantly with any of the landscape variables measured. Contrary to predictions, probabilities of brood parasitism decreased with increasing proportions of anthropogenic habitats surrounding nests. Probabilities of brood parasitism also decreased, but only slightly, as the breeding season progressed. Finally, Acadian Flycatcher nests were located significantly more often near natural (forest-water interface) edges than expected at random. Narrow corridors such as those along floodplain restoration projects do not necessarily create ecological traps for all forest species. Acadian Flycathcers, however, are one of the only forest-nesting Neotropical migrants that nest in narrow corridors and, therefore, may be less vulnerable to negative effects of fragmentation.Éxito de Nidificación de Empidonax virescens en Corredores de Bosque de Planicies Inundables

Naturalization of Developed Floodplains: An Integrated Analysis

SummaryReducing future flood damages and restoring natural services provided by floodplains is not as simple as buying levee districts from willing sellers and then breaching the levees. Removing agriculture from the floodplain can have a significant negative impact on the local economy, unless outdoor recreation, tourism or other activities are developed that are compatible with the naturalized floodplain. The value of the area for these activities depends in turn on the quality of the naturalization. We evaluated the potential for naturalization using a simulation model for an indicator group of plants, the moist‐soil plant community, that depends on the natural flooding cycle and provides food and shelter for a variety of valued species. Existing conditions and two alternative scenarios were evaluated by analyzing the frequency of successful growing seasons for moist soil plants using a 47‐year record of daily water levels and a hydraulic simulation model (for the scenarios). Results were expressed as color‐coded probabilities of plant success overlain on 3‐D maps of the floodplains—a visualization of results that was readily understood by stakeholders.One of the stakeholders, The Nature Conservancy, subsequently funded a more detailed study by our scientists of the Emiquon Floodplain Restoration Project, a 2,125‐ha agricultural drainage and levee district purchased for $18.3 million in 2000 by the Conservancy and located within our study reach on the Illinois River. Based on the results, the Conservancy plans to undertake a managed reconnection of the river and the floodplain at Emiquon, using gates in the levee to admit river water (and aquatic organisms) during the spring flood, but to exclude the unnatural, frequent summer floods that drown moist‐soil plants. The Conservancy intends the Emiquon Restoration to be a model not only for its floodplain restorations in the Upper Mississippi River Basin, but also a model for naturalization projects undertaken by state and federal agencies. Three papers from this project are cited extensively in the U.S. Army Corps of Engineers' Illinois River Basin Restoration Comprehensive Plan and Integrated Environmental Assessment and the plan includes recommendations for naturalizing the hydrology of the river and restoring moist‐soil vegetation (USACE 2006).The results from the project are also used in an introductory lecture for summer interns at the National Great Rivers Research and Education Center and have been the basis of the development of an economic module for the NSF curriculum development project on Interdisciplinary Modeling of Aquatic Ecosystems (Saito et al. 2005). Our co‐PIs and project information were among the resources used by graduate students in a project in Urban and Regional Planning at the University of Illinois to: (1) analyze the evolution of planning efforts on the Illinois River; (2) compare these efforts to planning efforts elsewhere; and (3) develop a framework for improved, integrated planning for the Illinois River (Fassero et al. 2001).

Perceptions of river managers of institutional constraints on floodplain restoration in the UK

The restoration of river environments has been of growing importance to river management and planning in the UK. The extension of ecological restoration to floodplains as well as river channels is more complex, partly because of the range of stakeholders and the diversity of relevant management institutions. This paper draws on a qualitative survey of river managers in the UK to identify institutional factors relevant to the success or failure of floodplain restoration projects.

Fish assemblages of perennial floodplain ponds of the Sacramento River, California (USA), with implications for the conservation of native fishes

AbstractTo assess the likelihood of enhancing native fish populations by means of floodplain restoration projects, habitat characteristics and fish assemblages of seven perennial floodplain ponds in Yolo Bypass, the primary floodplain of the Sacramento River, California (USA), were examined during summer 2001. Although all ponds were eutrophic, based upon high chlorophyll a or dissolved nutrient concentrations, relatively large shallow ponds generally exhibited higher specific conductivity and dissolved phosphorus concentrations than small deep ponds, which exhibited greater water transparency and total dissolved nitrogen concentrations. Using multiple gear types, 13 688 fishes comprising 23 species were collected. All ponds were dominated by alien fishes; only three native species contributing <1% of the total number of individuals and <3% of overall biomass were captured. Fish assemblage structure varied among ponds, notably between engineered vs. natural ponds, and was related to specific conductance, total dissolved solids and water transparency.

ASSESSMENT OF THE RESTORATION POTENTIAL OF THE LOGONE FLOOD‐PLAIN (CAMEROON)

Over the last thirty years, floodplain ecosystems in West Africa have been extensively damaged or destroyed by the construction of major agricultural and hydro‐electric infrastructure. In many cases this has induced a serious loss of biodiversity and reduced the potential to produce economic benefits for the local population from fishing, flood‐recession agriculture, dry‐season grazing and groundwater recharge. In 1993, in order to address the degradation of the Logone floodplain, the World Conservation Union initiated a floodplain‐restoration project.In order to study the feasibility and effectiveness of a larger‐scale restoration, a sophisticated one‐dimensional hydrodynamic model was developed. This paper describes the results of modelling various options for this restoration under three climatic scenarios (good, average, poor). Results indicate that, for ‘good’ years, up to 93% of the degraded floodplain can be re‐inundated through a major adjustment of the existing infrastructure, without compromising other floodplain uses such as the irrigated agriculture and reservoir fisheries. The extension of model use for restoration assessment in other floodplains is also examined.

Restoration strategies for river floodplains along large lowland rivers in Europe

1. Most temperate rivers are heavily regulated and characterised by incised channels, aggradated floodplains and modified hydroperiods. As a consequence, former extensive aquatic/terrestrial transition zones lack most of their basic ecological functions.2. Along large rivers in Europe and North America, various floodplain restoration or rehabilitation projects have been planned or realised in recent years. However, restoration ecology is still in its infancy and the literature pertinent to river restoration is rather fragmented. (Semi‐) aquatic components of floodplains, including secondary channels, disconnected and temporary waters as well as marshes, have received little attention, despite their significant contribution to biological diversity.3. Many rehabilitation projects were planned or realised without prior knowledge of their potential for success or failure, although, these projects greatly contributed to our present understanding of river–floodplain systems.4. River rehabilitation benefits from a consideration of river ecosystem concepts in quantitative terms, comparison with reference conditions, historical or others, and the establishment of interdisciplinary partnerships.5. We present examples from two large European rivers, the Danube and the Rhine, in which the role of aquatic connectivity has been extensively studied. The Danube delta with its diversity of floodplain lakes across an immense transversal gradient (up to 10 km) serves as a reference system for restoration projects along lowland sections of large rivers such as the Rhine in the Netherlands.

The use of economic and participatory approaches to assess forest development: a case study in the Ettrick Valley

The forest floodplain restoration project in the Ettrick Valley in the Borders Region of Scotland is a nationally important project which aims to expand and create forest floodplain habitats along the Upper Ettrick. The project aims to enhance existing habitats and wildlife whilst ensuring a partnership approach is maintained with the local community. The paper evaluates the project's success in achieving these aims, using two distinct approaches. The first, an economic approach uses the contingent valuation method to estimate the total economic value of the site. Results show that the mean willingness to contribute to this project on a one-off basis, was £10.39 per household. Aggregated over the Borders population, these results suggest that the project has a minimum value of approximately £450 000, as compared with an estimated cost of £350 000. The second approach uses participatory methodology — a Citizens’ Jury. A Citizens’ Jury consists of a small group of people, selected to represent the general public, who meet to deliberate upon a policy question. The Jury met to assess the project and to provide qualitative information on its value and importance to the local community. The Citizens’ Jury approved of the project, and although they did not place a monetary value upon it, they indicated that they valued the role it played in preserving the natural ecosystem, encouraging wildlife and educating the young. However, they were concerned about visitor access and the future management of the site.

Restoration of floodplain forests in Britain

Floodplain forests have almost completely disappeared from Britain. Throughout the temperate regions of Europe and North America they have been greatly reduced and many of the remainder are threatened. River control has altered the natural flooding and disturbance regime. However, changes in agricultural requirements and attitudes to river management and the need to water quality have created an opportunity for restoring some more natural river dynamics habitats. This paper presents a case for including managed and natural floodplain forests in river and floodplain restoration projects. Benefits would accrue for timber production, reduction of agricultural surpluses, nature conservation, fishing, water quality, river control and landscape quality. Limited practical experience of floodplain forest restoration in North America and continental Europe suggests that practical problems can be overcome.