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The concept of channel-forming ([Q.sub.cf]) or dominant discharge is now a cornerstone of river channel restoration design. Three measures of channel-forming discharge are most commonly applied: effective discharge ([Q.sub.eff]), bankfull discharge ([Q.sub.bf]), and a discharge of a certain recurrence interval ([Q.sub.ri]), which theoretically are similar in geomorphically stable channels. The latter two measures have become particularly widely applied in some channel restoration design procedures, often to the exclusion of [Q.sub.eff] analyses, despite the additional utility of [Q.sub.eff] analysis for most channel design problems. We quantify the three measures of [Q.sub.cf] for four case studies and then follow this with a synthesis of previously published studies to illustrate sources of variability. This synthesis suggests that agreement among the three measures of [Q.sub.cf] is best for snowmelt-hydrology, nonincised channels with coarse substrate. Departures from these conditions result in greater discrepancy between the measures. Channel incision produces [Q.sub.bf] far greater than [Q.sub.eff], and flashy hydrology is associated with generally larger, briefer, and more frequent [Q.sub.eff]. Regional mean or median values for the relative magnitudes of the three measures can be tightly constrained, but site to site variation is quite large. The construction of a cumulative sediment discharge curve and associated determination of [Q.sub.eff] allows quantification of the sediment budget of a channel for a given hydrologic regime, which provides process-based insight of drivers of current and future trajectories of channel stability, and is thus the recommended measure of channel-forming discharge. Reliance on only return-interval or bankfull discharge for channel design is not recommended for channel design activities. DOI: 10.1061/(ASCE)0733-9429(2007)133:7(831) CE Database subject headings: Channel design; Geomorphology; Stream improvement; Rivers; Restoration.

ABSTRACT During fall 2005 and spring 2006, habitat assessments and fish bioassessments were conducted at six sites on Five Mile Creek in Jefferson County, Alabama and two sites on nearby [...]

Various structural measures have been advocated for river restoration and habitat improvement schemes. The W-weir is one such structure that can be used in mobile bed alluvial rivers to diversify habitat and provide grade control. Laboratory studies have been carried out in a large-scale meandering channel with a mobile bed to investigate their effects on flow and sediment transport processes. A W-weir placed immediately downstream of a riffle section created a strongly three-dimensional flow pattern and high-turbulence zones. Two adjacent scour holes of different depths and substrate are formed under clearwater and live bed conditions. The continuity of sediment transport along the channel was not interrupted by the structure and the upstream afflux is minimal. Overbank flow significantly influenced the action of the weir and the scour hole was shifted closer to the structure. In a relatively tight bend followed by a short crossover reach, the weir may affect bed load transport pathways in the downstream bend. Finally, the study provides insights to guide their design for restoration projects. DOI: 10.1061/(ASCE)0733-9429(2007)133:6(596) CE Database subject headings: Hydraulic structures; Weirs; Rivers; Restoration; Scout: Turbulence.

A pumping test and corresponding analysis that permit calculation of several hydrogeological parameters appearing in the Hunt (2003) solution for stream depletion caused by ground water abstraction from a well beside a stream is described. The results show that a pumping test must be carried out for a sufficiently long period of time to allow leakage from the stream to have a significant influence upon the measured drawdown curve.

Although many streams in North America have been rehabilitated to improve the habitat of salmonids, little is known about the long-term impacts of such practices on salmonid habitats and on river dynamics. The success of these improvement schemes is often assessed a short time after the work is completed and is usually based on changes in the targeted biological populations. This article examines the long-term effects of bank-cover deflectors on the physical fish habitat and on the channel morphology. The study was conducted on Lawrence Creek, a small stream in Wisconsin, where trout habitat had been affected negatively by intense cattle grazing. Data on the physical habitat and on channel morphology were collected on a 600-m-long reach in 1963 (immediately prior to the rehabilitation work), in 1966, and in 1999. In the upstream section, the channel flows through a moraine deposit where bed material is coarser than the material of the outwash plain found in the downstream portion of the reach. Results indicate that fish habitat in 1999 was better than in 1963 but has deteriorated substantially since 1966. Pool area increased from 267 [m.sup.2] to 625 [m.sup.2] between 1963 and 1966, but has decreased to 488 [m.sup.2] since then. Most of this deterioration, however, is concentrated in the morainic section. In the outwash plain, the deflectors are still in good condition, and the area occupied by pools has remained constant since 1966. In the morainic section, most structures are no longer efficient and the channel is unstable due to high bed-shear stress values, which entrain bed and bank erosion. Effective long-term rehabilitation schemes should therefore carefully consider the varying sensitivity of river reaches due to different geomorphic contexts. Key Words: flow deflectors, geomorphic context, physical fish habitat, stream restoration.

An overview is presented on threats to riverine biodiversity in tropical Asian regions, such as deforestation, pollution, over-harvesting, dams, and flow regulation. Proposed solutions to these threats include improved public education on environmental issues and increased political commitment to conservation efforts and legal protections.

This article examines the negative effects of river impoundment on populations of freshwater mussels in Oklahoma state. Topics discussed include observed mussel extinction gradients, and conservation management plans to overcome the effects of damming rivers.

Aquatic habitats in a deeply incised sand-bed channel were modified by adding 1,380 t of stone and planting dormant willow posts. Restoration structures (groin extensions and longitudinal toe protection) were designed as complements to existing channel stabilization works. Prior to restoration, base-flow aquatic habitats were characterized by uniform conditions, little woody debris or riparian vegetation, shallow depths, and sandy bed material. The stage-discharge relationship, channel geometry, and bed material size were unaffected by restoration, but the average depth of scour holes adjacent to extended groins increased from 32 cm to 72 cm, and pool habitat in the lower half of the study reach increased from 2.9% to 14% of water surface area. Median water depth at base flow increased from 9 cm to 15 cm. Woody vegetation cover on one side of the channel increased from 38% to 78%. Fish numbers tripled, median fish size increased by 50%, and the number of species increased from 14 to 19. Groin extensions experienced partial failure due to erosion of sand from underneath stones.

ABSTRACT Historically, the Alsea and Yaquina rivers in the Oregon Coast Range were densely vegetated with diverse riparian areas that supported large runs of salmon. Human disturbance of vegetation along [...]

Large-scale river training works have been carried out in the Hunter valley since 1955 in response to flood-driven channel changes. Vegetation was planted on in-channel benches induced by river training works to consolidate the deposits and to increase channel boundary roughness. Exotic species of vegetation such as willows and poplars were previously used. In 1983, ten trial sites were planted with various species of native vegetation. Survival rates were evaluated in 1987 and 1997. The most successful species planted was Eucalyptus camaldulensis with an overall survival rate of 77 per cent in 1997. The Acacia species were found to be short-lived, exhibiting a significant decline in survival rates between 1987 and 1997. Survival rates for most species were higher on sand-bed than on gravel-bed sites. This difference may be attributed to better drainage on benches at the sand-bed sites. Investigations of flood disturbance showed that between 1983 and 1997 the sites were flooded between four and 13 times. The survival rates of Grevillea robusta and Eucalyptus melliodora trees were negatively correlated with the total number of recorded floods at each site. Poor natural regeneration of planted species is attributed to a combination of periodic flooding, intensive weed growth, low light intensities at ground level and grazing disturbance. These trials were not well designed for statistical analysis but provide valuable long-term information on the suitability of various species for planting in riparian rehabilitation programs. Such information is of relevance not only to river and catchment management authorities, but also to community groups.