Stream Restoration Techniques Research Articles

Assessing stream channel restoration: the phased recovery framework

Channel reconfiguration is one of the most common and costly stream restoration techniques, though its effectiveness is frequently questioned. Project monitoring often tracks changes in macroinvertebrate communities and other responses for a 5‐year period. However, channel reconfiguration is a documented disturbance to stream ecosystems, suggesting that this form of restoration initiates succession over longer time frames than monitoring typically captures. To address the role of succession in stream ecosystem recovery, we developed the Phased Recovery Framework (PRF) which proposes benchmarks represented by predictable habitat structure and community composition based on project age. The PRF was tested across nine stream restoration projects in western Montana, ranging in age from 1 to 18 years, each paired with an established reference system. We tested for differences in channel form, habitat character, and macroinvertebrate community composition. While restoration established desired channel form, most biotic variables had not recovered to reference condition even for the oldest projects. Across all sites, phases of the PRF were poor predictors of response. However, analyzing responses to reconfiguration independently for sites in watersheds with unimpaired water quality versus those experiencing excessive nutrient enrichment (i.e. impaired sites) indicated that biological variables converged on reference conditions at unimpaired sites, but diverged across impaired reaches. These large‐scale anthropogenic influences may play a stronger role in recovery than do changes to channel form and need to be incorporated into project design and success criteria. Assessment of the PRF suggests that short‐term monitoring is not likely to produce reliable indicators of effectiveness without incorporating locally appropriate change associated with watershed impairment and successional progression.

Hydro-morphological parameters generate lifespan maps for stream restoration management

Anthropogenic, eco-morphological degradation of lotic waters necessitates laws, directives, and voluntary actions involving stream restoration and habitat enhancement. Research and engineering efforts are establishing a vast number of stream restoration planning approaches, design testing frameworks, construction techniques, and performance evaluation methods. As the practice of restoration scales up from an individual action at a single site to sequences of actions at many sites in a long river segment, a primary question arises as to the lifespan of such a sequence. This study develops a new framework to identify relevant parameters, design criteria and survival thresholds for ten multidisciplinary restoration techniques, adequate for site-scale to segment-scale application, in a comprehensive review: (1) bar and floodplain grading; (2) berm setback; (3) vegetation plantings; (4) riprap placement; (5) sediment replenishment; (6) side cavities; (7) side channel and anabranches; (8) streambed reshaping; (9) structure removal; and (10) placement of wood in the shape of engineered logjams and rootstocks. Survival thresholds are applied to a sequence of proposed habitat enhancement features for the lower Yuba River in California, USA. Spatially explicit hydraulic and sediment data, together with numerical model predictions of the measures, were vetted against the survival thresholds to produce discharge-dependent lifespan maps. Discharges related to specific flood-return periods enabled probabilistic estimates of the longevity of particular design features. Thus, the lifespan maps indicate the temporal stability of particular stream restoration and habitat enhancement features and techniques. Areas with particularly low or high lifespans help planners optimise the design and positioning of restoration features.

URBAN STREAM RESTORATION AND APPLIED PRACTICES IN NORTHEAST ILLINOIS

INTRODUCTION: In-stream and watershed dynamics in urban and urbanizing areas have significant impacts on local property and infrastructure, as well as the quality of the stream itself including: water quality, habitat, physical characteristics, and biodiversity. As land development occurs, natural vegetation and exposed soils are converted to buildings, pavement and other impervious surfaces. This leads to increased runoff during storm events as well as decreasing the time that it takes that stormwater to reach streams, wetlands, and other stormwater storage and conveyance systems. These hydrologic changes in a watershed often occur at a rapid pace which results in rapid destabilization and degradation of streams and rivers. Rivers and streams are naturally dynamic systems. They naturally erode and reshape themselves based on changes to the watershed or the stream itself. Erosion and deposition are natural processes that have always been important components of stream systems and in and of themselves are not undesirable. When natural stream dynamics are rapidly accelerated, however, an entire series of negative impacts to the stream and the biological systems that are depended on the stream occur. Rapid destabilization of streams often leads to significant bank and bed erosion that negatively impact stream health and frequently leads to negative impact to property, buildings and structures, as well as public infrastructure. Past approaches to stream bank and bed stabilization often involved channelization, armoring, and other gray infrastructure techniques to protect public and private property in the effected reaches of streams and rivers without taking into account the overall stream system dynamics. Early stabilization efforts frequently led to other unintended consequences by accelerating the rate of bank and bed erosion in untreated reaches, inadvertent flooding, and other infrastructure impacts. The complex nature of stream dynamics and fluvial geomorphology when applied to urban stream systems and significantly modified watersheds require the need for detailed analysis of the morphology of the stream. Consideration of the complex factors and processes that make up fluvial morphology are critical when selecting practices or methods of stream restoration. Many agencies and cooperative partners work to accumulate and analyze case studies and detailed research in order to develop a method of evaluating and prescribing different stream restoration techniques based on the morphologic conditions in the stream reach (Lyn D.A., and Newton J.F., 2015). An accumulation of case studies, research, and scholarly work on stream restoration techniques and practices helps shape and inform designers across multiple agencies in order to effectively select and design restoration practices. Ultimately, in urban streams, the designer is working to establish a condition of dynamic equilibrium in the treated stream reach. Dynamic equilibrium is defined as a stream reach that is in balance with sediment transport, aggradation, degradation, and bank and bed erosion. When those characteristics are in balance based on the inputs of sediment within the watershed, the bed load and sediments the stream transports, and discharge rate and volume, then the stream is considered to be in a relatively stable state (FISRWG, 1998). The selection then of stream restoration and stabilization practices in urban areas is dependent on not only the reach being treated, but also on the overall watershed dynamics. In addition to the physics of the actual practices implemented, including resistance to shear stresses and velocity of the water flow within the stream channel being treated, the practices must also take into account the larger picture of stream dynamics including sediment delivery and transport, within the watershed and not just within the treated reach. Successful urban stream restoration and stabilization techniques mimic the structures found in more undisturbed systems through the utilization of similar materials in an engineered configuration. In many streams the use of a combination of hard and soft armorment and stabilization solutions including stone, woody debris materials, modern geosynthetic reinforcement devices and native vegetation to stabilize and naturalize stream channels, thereby provided enhanced habitat, better water quality, and protecting property and infrastructure.

Vegetation survey in nature-friendly small streams for each protection method

Riparian vegetation distribution patterns and diversity relative to various fluvial geomorphic channel patterns, stream bank stabilization methods, and stream flow processes are described and interpreted for selected nature-friendly small stream bank protection of Goesan, central Korea. Idong Stream Pilot Project, which began in May 2003 and finished in December 2003, was selected to develop effective methods which was nature-friendly stream bank protection. The project aim to maintain or increase stream bank stabilization ecosystem goods and services while protecting downstream and stream bank ecosystem. A number of protecting methods which were a Flight of fieldstone, Vegetation block, Green river block, Stone net, Green environment block, Eco friendly cobble, Vegetation mat and Geo-green cell and Firefly block were applied on the bank of Idong stream. The stream sites have been monitored about vegetation conditions each method in 2007. We selected six points to separately investigate in left and right bank. The main purpose of this study was to find out suitable methods and to improve stream restoration techniques for ecosystem. On the stream bank, H environment block method (9.7) was the highest average of vegetation coverage and Firefly block method (3.87) was the lowest average in applied methods.

Bayesian modeling of the assimilative capacity component of nutrient total maximum daily loads

Implementing stream restoration techniques and best management practices to reduce nonpoint source nutrients implies enhancement of the assimilative capacity for the stream system. In this paper, a Bayesian method for evaluating this component of a total maximum daily load (TMDL) load capacity is developed and applied. The joint distribution of nutrient retention metrics from a literature review of 495 measurements was used for Monte Carlo sampling with a process transfer function for nutrient attenuation. Using the resulting histograms of nutrient retention, reference prior distributions were developed for sites in which some of the metrics contributing to the transfer function were measured. Contributing metrics for the prior include stream discharge, cross‐sectional area, fraction of storage volume to free stream volume, denitrification rate constant, storage zone mass transfer rate, dispersion coefficient, and others. Confidence of compliance (CC) that any given level of nutrient retention has been achieved is also determined using this approach. The shape of the CC curve is dependent on the metrics measured and serves in part as a measure of the information provided by the metrics to predict nutrient retention. It is also a direct measurement, with a margin of safety, of the fraction of export load that can be reduced through changing retention metrics. For an impaired stream in western Oklahoma, a combination of prior information and measurement of nutrient attenuation was used to illustrate the proposed approach. This method may be considered for TMDL implementation.

A Review of Stream Restoration Techniques and a Hierarchical Strategy for Prioritizing Restoration in Pacific Northwest Watersheds

Millions of dollars are spent annually on watershed restoration and stream habitat improvement in the U.S. Pacific Northwest in an effort to increase fish populations. It is generally accepted that watershed restoration should focus on restoring natural processes that create and maintain habitat rather than manipulating instream habitats. However, most process-based restoration is site-specific, that is, conducted on a short stream reach. To synthesize site-specific techniques into a process-based watershed restoration strategy, we reviewed the effectiveness of various restoration techniques at improving fish habitat and developed a hierarchical strategy for prioritizing them. The hierarchical strategy we present is based on three elements: (1) principles of watershed processes, (2) protecting existing high-quality habitats, and (3) current knowledge of the effectiveness of specific techniques. Initially, efforts should focus on protecting areas with intact processes and high-quality habitat. Following a watershed assessment, we recommend that restoration focus on reconnecting isolated high-quality fish habitats, such as instream or off-channel habitats made inaccessible by culverts or other artificial obstructions. Once the connectivity of habitats within a basin has been restored, efforts should focus on restoring hydrologic, geologic (sediment delivery and routing), and riparian processes through road decommissioning and maintenance, exclusion of livestock, and restoration of riparian areas. Instream habitat enhancement (e.g., additions of wood, boulders, or nutrients) should be employed after restoring natural processes or where short-term improvements in habitat are needed (e.g., habitat for endangered species). Finally, existing research and monitoring is inadequate for all the techniques we reviewed, and additional, comprehensive physical and biological evaluations of most watershed restoration methods are needed.