LARGE‐WOOD LOADING FROM NATURAL AND ENGINEERED PROCESSES AT THE WATERSHED SCALE

Large wood, both live and dead, is essential for producing complex habitat in many streams, especially in forested watersheds that support salmonid populations. The addition of engineered wood structures is a common approach taken in many streams where past watershed management practices have resulted in reduced wood loading. We examined six 300‐m stream reaches in the Lagunitas Creek watershed, Northern California, to determine (i) the distribution of large wood in the bankfull channel and 10‐year floodplain, (ii) the influence of large wood on the size and distribution of pools and (iii) whether streams with engineered wood structures had greater diversity of pool habitat to support salmonid populations. We found that the amount of large wood in the bankfull channel and the amount available for recruitment from the 10‐year floodplain were highly variable among and within reaches examined and largely dependent on the local geomorphic setting. Stream reaches with engineered wood structures had elevated pool frequencies relative to reaches without these structures, suggesting a higher capacity to support salmonids during critical life stages. Among large wood pieces that had a strong influence on pool formation, 23% had an attached root wad and 66% were part of a cluster. All of the study reaches we examined had lower volumes of large wood in their bankfull channels than similar stream types with natural wood‐loading levels, suggesting that increased additions of large wood could provide ecosystem benefits over time. These principles can be understood and transferred effectively to other watersheds using a framework of wood‐loading process domains. Copyright © 2012 John Wiley & Sons, Ltd.     

Herbaceous Versus Forested Riparian Vegetation: Narrow and Simple Versus Wide,Woody and Diverse Stream Habitat

We investigated interactions of riparian vegetative conditions upon a suite of channel morphological variables: active channel width, variability of width within a reach, large wood frequency, mesoscale habitat distributions, mesoscale habitat diversity, median particle size and per cent fines. We surveyed 49 wadeable streams, 45 with low levels of development, throughout the Upper Little Tennessee River Basin in the Southern Appalachians. Conversion of riparian forest to grass has reduced aquatic habitat area (quantified by active channel width), channel width variability, wood frequency, mesoscale habitat diversity and obstruction habitat (wood and rock jams), and such conversion has increased the fraction of run and glide habitat. Channels with grassy riparian zones were only one‐third to three‐fifths of the width of channels with forested riparian zones, and channels with grassy or narrow forested riparian zones were nearly devoid of wood. Particle size metrics were strongly affected by stream power and agricultural cover in the basin, but the data suggest that elimination of riparian forest reduces median bed particle size. Results indicate that even modest increases in the extent and width of forested riparian buffers would improve stream habitat conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

IDENTIFICATION OF FLUVIAL WOOD USING GOOGLE EARTH

Fluvial wood has long been known to enhance stream complexity by creating aquatic habitat and by increasing complexity in channel hydraulics and morphology. Although the presence and dynamics of large wood in river floodplains have been studied in a multitude of settings due to its importance in monitoring and managing ecohydrologic systems, limitations occur when studying fluvial wood on a basin scale. I postulate that with the employment of Google Earth, satellite images may be used to identify large wood and measure floodplain width across broader spatial scales previously inhibited by expensive and incomplete geospatial data. In this study, large wood was correctly identified within the floodplain of the Queets River, Washington, USA, through Google Earth; however, correct identification within the wetted channel was only possible during low flow if at least 50% was above water level. Within the study area, fluvial channel widths are measured as well. Google Earth proves to be an effective tool to discern large wood across greater spatial scales if the high‐resolution imagery is available for the study area. Results of statistical analyses derived from the downstream hydraulic geometry of the river reveal that this channel is influenced by bankfull width, the orientation of the wood to the channel, and whether it is located on a bar or within the wetted channel. In addition, wood counts analyzed in the context of the geometry of the river indicate that the fluvial wood has an influence on overall channel behavior. Copyright © 2013 John Wiley & Sons, Ltd.     

Spatial distribution of large wood jams in streams related to stream‐valley geomorphology and forest age in Northern Michigan

Geomorphology at the scale of stream valleys influences smaller scale processes that give rise to spatially distributed patches, including large wood jams (LWJ) in streams. Understanding the spatial distribution of LWJ along streams with reference to large‐scale geomorphology is valuable for understanding stream and riparian interactions, and may be critical for effective stream management and restoration. We surveyed the locations of LWJ along 18 stream segments within study areas defined by stream‐valley geomorphology. The objective of this study was to test the prediction that LWJ in this system will be aggregated in areas defined by stream‐valley geomorphology, but be randomly distributed at smaller scales. The spatial distribution of LWJ was analysed by a one‐dimensional K‐function analysis capable of detecting aggregated, random and segregated patterns at different scales. The prediction that LWJ aggregate in areas defined by stream‐valley geomorphology was supported: LWJ aggregated at scales up to several kilometres in three streams. LWJ also was segregated at smaller scales in two of these streams; this was detectable when several stream valley segments were considered together. The prediction that LWJ would be randomly distributed at smaller scales was supported at most smaller scales for most streams. In fact, 40% of individual stream valley segments contained LWJ that were randomly distributed at all scales. Twenty‐seven per cent of individual stream valley segments showed segregated LWJ distributions. Large‐scale aggregation of LWJ evidences the need to select reference reaches that encompass several geomorphic patches at the scale of the stream valley. Segregated patterns of LWJ distributions evidence opportunities to better understand the relationships between hydraulic systems, material transport dynamics and riparian forests. Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of large woody debris on surface structure and aquatic habitat in forested streams,southern interior British Columbia,Canada

It is well known that large woody debris (LWD) plays an important functional role in aquatic organisms' life. However, the influence of LWD on channel morphology and aquatic environments at watershed levels is still unclear. The relationships between wood and surface structure and aquatic habitat in 35 first through fifth order streams of southern interior British Columbia were investigated. Study streams in the channel networks of the study watersheds were classified into four size categories based on stream order and bankfull width: Stream size I: bankfull width was less than 3 m, Stream size II: 3–5 m, Stream size III: 5–7 m, Stream size IV: larger than 7 m. We found the number of functional pieces increased with stream size and wood surface area in stream sizes I, II and III (24, 28 and 25 m²/100 m², respectively) was significantly higher than that in stream size IV (12 m²/100 m²). The contribution of wood pieces to pool formation was 75% and 85% in stream sizes II and III, respectively, which was significantly higher than those in stream size I (50%) and size IV (25%). Between 21% and 25% of wood pieces were associated with storing sediment, and between 20% and 29% of pieces were involved in channel bank stability in all study streams. Due to long‐term interactions, LWD in the intermediate sized streams (Size II and III) exhibited much effect on channel surface structure and aquatic habitats in the studied watersheds. Copyright © 2008 John Wiley & Sons, Ltd.     

Geomorphic effects of large wood jams on a sub‐antarctic mountain stream

Dead wood pieces, especially when organized in jams, play an important geomorphic role in streams because of the effects on flow hydraulics, pool formation and sediments storage. The increase in stream morphological diversity and complexity also exerts an important ecological role. This work reports on geomorphic role of large wood (LW) pieces and jams in a third‐order mountain stream located in the Southern Tierra del Fuego (Argentina), and draining an old‐growth Nothofagus‐forested basin not influenced by the beavers damming activity. Even if the in‐stream number of wood pieces (length >1 m; diameter >0.1 m) is comparable to that observed in other climatic areas, the slow growth of the Nothofagus forest causes a lower wood abundance in terms of volumetric load. Because of the relatively small dimensions of the surveyed LW pieces, almost 70% of them demonstrated to have been fluvial transported and also the wood jams reflect the apparent dynamic nature of wood in the channel. Wood jams exert a significant influence on the channel morphology, representing almost half of the drop caused by steps and being responsible for the creation of 30% of the pools. LW‐forced pool volume is strongly and positively correlated to the height of the LW jam. The geomorphic influence of LW jams is also exerted by a considerable sediment storing capacity. Copyright © 2008 John Wiley & Sons, Ltd.     

Transient organic jams in Puerto Rican mountain streams after hurricanes

Extreme storms in forested environments commonly increase inputs of coarse particulate organic matter (CPOM) and large wood (LW) to streams. Protruding boulders and bedforms, mid‐channel bars, and standing trees can trap CPOM and LW. These organic accumulations can become large enough to span the bankfull channel width, or the accumulations can be predominantly along the channel margins. We refer to both types of accumulations as transient organic jams (TOJs). TOJs can create diverse geomorphic and ecological effects in channel and floodplain environments. We use data collected from mountain streams of the Luquillo Mountains of north‐eastern Puerto Rico following September 2017 Hurricanes Irma and Maria. We examine the location, characteristics, and geomorphic effects of TOJs in channel segments representing diverse drainage areas and channel gradients. We ask three questions: (a) Does the downstream spacing of TOJs correlate with variables such as drainage area or channel gradient? (b) What variables best predict the volume of organic matter within individual TOJs or within a channel segment? And (c) is there a threshold within a river network that separates channel segments with channel‐spanning versus marginal TOJs? Datasets include multiple TOJs along each of 12 stream segments and presence/absence of channel‐spanning TOJs along an additional six streams. Data analysis with multiple linear regressions indicates that downstream spacing, average volume, and total volume per channel length of TOJs correlate significantly with bankfull channel width. Using the akaike information criterion with correction (AICc) model selection method, Strahler stream order has the most influence on the probability of TOJs being marginal or spanning.     

CONTROLS ON THE LONGITUDINAL DISTRIBUTION OF CHANNEL‐SPANNING LOGJAMS IN THE COLORADO FRONT RANGE,USA

Channel‐spanning logjams completely span the active channel and create longitudinal discontinuities of the water surface and stream bed across at least two‐thirds of the channel width. These jams disproportionately affect channel process and form relative to smaller jams that do not span the entire channel width. We analyze a spatially extensive dataset of 859 channel‐spanning jams distributed along 124 km of 16 distinct rivers on the eastern side of Rocky Mountain National Park, Colorado, USA, with drainage areas spanning 2.6 to 258 km² and diverse valley geometry and forest stand age. We categorized valley geometry in terms of lateral confinement (confined, partly confined, or unconfined), which correlates with gradient. Jams exhibit substantial downstream variability in spacing at channel lengths of 10²–10³ m. The number of jams within a reach is explained by a statistical model that includes drainage area, valley type (lateral confinement), and channel width. Longitudinal spacing of jams drops substantially at drainage areas greater than ~20 km², although jam spacing exhibits tremendous variability at smaller drainage areas. We interpret the lack of jams at larger drainage areas to reflect increasing transport capacity for instream wood. We interpret the variability in jam spacing at small drainage areas to reflect local controls of valley geometry and associated wood recruitment and fluvial transport capacity. Our results suggest that management of instream wood designed to facilitate the formation of channel‐spanning jams can be most effectively focused on smaller drainage areas where these jams are most abundant in the absence of management that alters instream wood recruitment or retention. Unmanaged streams in the study region with drainage area <60 km² have ~1.1 channel‐spanning jams per 100 m length of stream. The cumulative effects of these jams on instream storage of sediment and organic matter, hyporheic exchange, instream habitat, stream metabolism, and channel–floodplain connectivity are likely to be enormous. Copyright © 2012 John Wiley & Sons, Ltd.     

A LIDAR‐DERIVED EVALUATION OF WATERSHED‐SCALE LARGE WOODY DEBRIS SOURCES AND RECRUITMENT MECHANISMS: COASTAL MAINE,USA

In‐channel large woody debris (LWD) promotes quality aquatic habitat through sediment sorting, pool scouring and in‐stream nutrient retention and transport. LWD recruitment occurs by numerous ecological and geomorphic mechanisms including channel migration, mass wasting and natural tree fall, yet LWD sourcing on the watershed scale remains poorly constrained. We developed a rapid and spatially extensive method for using light detection and ranging data to do the following: (i) estimate tree height and recruitable tree abundance throughout a watershed; (ii) determine the likelihood for the stream to recruit channel‐spanning trees at reach scales and assess whether mass wasting or channel migration is a dominant recruitment mechanism; and (iii) understand the contemporary and future distribution of LWD at a watershed scale. We utilized this method on the 78‐km‐long Narraguagus River in coastal Maine and found that potential channel‐spanning LWD composes approximately 6% of the valley area over the course of the river and is concentrated in spatially discrete reaches along the stream, with 5 km of the river valley accounting for 50% of the total potential LWD found in the system. We also determined that 83% of all potential LWD is located on valley sides, as opposed to 17% on floodplain and terrace surfaces. Approximately 3% of channel‐spanning vegetation along the river is located within one channel width of the stream. By examining topographic and morphologic variables (valley width, channel sinuosity, valley‐side slope) over the length of the stream, we evaluated the dominant recruitment processes along the river and often found a spatial disconnect between the location of potential channel‐spanning LWD and recruitment mechanisms, which likely explains the low levels of LWD currently found in the system. This rapid method for identification of LWD sources is extendable to other basins and may prove valuable in locating future restoration projects aimed at increasing habitat quality through wood additions. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydrologic spiralling: the role of multiple interactive flow paths in stream ecosystems

We develop and illustrate the concept of ‘hydrologic spiralling’ using a high‐resolution (2 × 2 m grid cell) simulation of hyporheic hydrology across a 1.7 km² section of the sand, gravel and cobble floodplain aquifer of the upper Umatilla River of northeastern Oregon, USA. We parameterized the model using a continuous map of surface water stage derived from LIDAR remote sensing data. Model results reveal the presence of complex spatial patterns of hyporheic exchange across spatial scales. We use simulation results to describe streams as a collection of hierarchically organized, individual flow paths that spiral across ecotones within streams and knit together stream ecosystems. Such a view underscores the importance of: (1) gross hyporheic exchange rates in rivers, (2) the differing ecological roles of short and long hyporheic flow paths, and (3) the downstream movement of water and solutes outside of the stream channel (e.g. in the alluvial aquifer). Hydrologic spirals underscore important limitations of empirical measures of biotic solute uptake from streams and provide a needed hydrologic framework for emerging research foci in stream ecology such as hydrologic connectivity, spatial and temporal variation in biogeochemical cycling rates and the role of stream geomorphology as a dominant control on stream ecosystem dynamics. Copyright © 2008 John Wiley & Sons, Ltd.     

Reintroducing wood to streams in agricultural landscapes: changes in velocity profile,stage and erosion rates

Historically, perceived increases in erosion and flooding levels have been attributed to in‐stream wood and used to justify its removal from streams and rivers around the world. More recently, recognition of the adverse morphological and biological impacts caused by this removal has led to rehabilitation projects that actively reintroduce wood to streams. However, a perception remains amongst some members of the general community that wood additions increase the likelihood of flooding and erosion in the target streams. To test whether there was a basis for this perception, we experimentally added wood to eight streams across southwest Victoria and Gippsland, Australia. The velocity, stage and bed and bank erosion rates were compared with those of unaltered reaches. We detected localized changes in the velocity and stage parameters but that these were unlikely to operate at the reach‐scale. Bed erosion rates, where maximum erosion was assumed if pins were not recovered, showed increased erosion due to wood additions but this was not supported by channel shape analyses, which identified short‐term increases in the variability of the channel shape, followed by longer‐term stability at treatment sites. We found no clear evidence of increased longer‐term rates of erosion or flooding associated with the introduction of wood to streams over the 18‐month study period. It remains important to carefully design rehabilitation works, but the lack of adverse effects on stream morphology and increased variability of the in‐stream environment suggests improved habitat diversity, supporting the use of wood addition as a stream rehabilitation technique. Copyright © 2008 John Wiley & Sons, Ltd.     

APPLICATION OF AERIAL DIGITAL PHOTOGRAPHY FOR MACROPHYTE COVER AND COMPOSITION SURVEY IN SMALL RURAL STREAMS

Macrophytes are a key biological component in many fluvial ecosystems. In altered streams, they can become highly dominant features, covering extensive parts of the channel with cascading effects on stream conditions and biological composition. The aim of this study is to examine the possibility of using information collected by aerial digital photography‐spectral analysis (ADP‐SA) as an alternative, cost‐effective methodology to the commonly used spectral procedure at a large (section) scale, and to the ground level visual survey (gridded frame) at a smaller (organism) scale. Cladophora glomerata and Nasturtium officinale, were selected as the targeted macrophyte species and classified at the same time (species relative cover) by using the three methodologies. Our findings show that the ADP‐SA methodology was able to detect species and relative cover in similar accuracy (≤10% differences) at the two spatial scales. ADP‐SA had a better spatial resolution than both the hyperspectral and the visual methodology (4 cm vs. 1 m and 10 cm, respectively) and was capable to differentiate submerged from emergent plants. However, on a smaller scale, ground level work is suitable and essential for detecting rarer species and is not hindered by weather, canopy cover or multi‐layered plant composition. ADP‐SA can therefore add a cost‐effective and nonsubjective practice to the existing tool kit of macrophyte surveys, particularly in small streams, which require high spatial resolution. Copyright © 2013 John Wiley & Sons, Ltd.     

The effect of land use on channel geometry and sediment distribution in gravel mantled bedrock streams,Illinois River watershed,Arkansas

Headwater stream morphology is a direct reflection of watershed characteristics and therefore can inform our understanding of anthropogenic influence on channel geometry and sediment dynamics. Little knowledge of the geomorphology of headwater streams in the Ozark Plateaus region of northwest Arkansas exists. The Illinois River watershed, in northwest Arkansas, is of critical interest within the region because of land use changes in the headwaters due to rapid population growth. A mixture of forest and agricultural (open pasture and poultry houses) land use dominates the watershed, but urban areas are rapidly expanding. These land use types: forest, agriculture and urban are an effective proxy for increasing anthropogenic disturbance. Analysis of longitudinal profile, cross‐section and sediment distribution in streams from each land use type shows a strong trend of increasing slope and channel cross‐sectional area with a greater degree of anthropogenic disturbance. Additionally, urban streams are characterized by the presence of exposed bedrock in the stream bed, while agricultural and forested streams are gravel mantled. These data have important implications for current and future stream management policies and practices regionally. Copyright © 2010 John Wiley & Sons, Ltd.     

Geomorphic applications of stream‐gage information

In the United States, several thousand stream gages provide what typically is the only source of continuous, long‐term streamflow and channel‐geometry information for the locations being monitored. In this paper, the geomorphic content of stream‐gage information, previous and potential applications of stream‐gage information in fluvial geomorphic research and various possible limitations are described. Documented applications include studies of hydraulic geometry, channel bankfull characteristics, sediment transport and channel geomorphic response to various types of disturbance. Potential applications include studies to determine the geomorphic effectiveness of large floods and in‐stream habitat change in response to disturbance. For certain applications, various spatial, temporal and data limitations may render the stream‐gage information of limited use; however, such information often is of considerable value to enable or enhance geomorphic investigations. Published in 2008 by John Wiley & Sons, Ltd.     

Hydrogeomorphic and Biotic Drivers of Instream Wood Differ Across Sub‐basins of the Columbia River Basin,USA

Instream wood promotes habitat heterogeneity through its influence on flow hydraulics and channel geomorphology. Within the Columbia River Basin, USA, wood is vital for the creation and maintenance of habitat for threatened salmonids. However, our understanding of the relative roles of the climatic, geomorphic, and ecological processes that source wood to streams is limited, making it difficult to identify baseline predictions of instream wood and create targets for stream restoration. Here, we investigate how instream wood frequency and volume differ between seven sub‐basins of the interior Columbia River Basin and what processes shape these differences within these sub‐basins. We collected data on wood volume and frequency, discharge and stream power, and riparian and watershed forest structure for use in modelling wood volume and frequency. Using random forest models, we found that mean annual precipitation, riparian tree cover, and the individual watershed were the most important predictors of wood volume and frequency. Within sub‐basins, we used linear models, finding that some basins had unique predictors of wood. Discharge, watershed area, or precipitation often combined with forest cover, riparian conifer, and/or large tree cover in models of instream large wood volume and frequency. In many sub‐basins, models showed at least one hydrologic variable, indicative of transport competence and one ecological variable, indicative of the reach or upstream watershed's capability to grow measurable instream wood. We conclude that basin‐specific models yield important insights into the hydrologic and ecological processes that influence wood loads, creating tractable hypotheses for building predictive models of instream wood. Copyright © 2015 John Wiley & Sons, Ltd.     

Wood‐induced backwater effects in lowland streams

Placement of wood in streams has become a common method to increase ecological value in river and stream restoration and is widely used in natural environments. Water managers, however, are often hesitant to introduce wood in channels that drain agricultural and urban areas because of backwater effect concerns. This study aims to better understand the dependence of wood‐induced backwater effects on cross‐sectional area reduction and on discharge variation. A newly developed, one‐dimensional stationary model demonstrates how a reduction in water level over the wood patch significantly increases directly after wood insertion. The water level drop is found to increase with discharge, up to a maximum level. If the discharge increases beyond this maximum, the water level drop reduces to a value that may represent the situation without wood. This reduction predominately depends on the obstruction ratio, calculated as the area covered by wood in the channel cross section divided by the total cross‐sectional area. The model was calibrated with data from a field study in four lowland streams in the Netherlands. The field study showed that morphologic adjustments in the stream and reorientation of the woody material reduced the water level reduction over the patches in time. The backwater effects can thus be reduced by optimizing the location where wood patches are placed and by manipulating the obstruction ratio. The model can function as a generic tool to achieve a stream design with wood that optimizes the hydrological and ecological potential of streams.     

Riparian Vegetation Communities of the American Pacific Northwest are Tied to Multi‐Scale Environmental Filters

Riparia surrounding low‐order streams are dynamic environments that often support distinct biodiversity. Because of their connection to nearby uplands, riparian vegetation communities at these streams respond to many environmental filters—climatic, physical, chemical or biotic factors—that restrict what species can occur at a given location from within larger regional species pools. In this study, we examined how environmental filters originating at the landscape, watershed and reach scales correspond to riparian plant community composition across the interior Columbia and upper Missouri River basins, USA. We correlated riparian vegetation to environmental filters, identified unique communities and partitioned the variance within riparian vegetation data among filters originating at different scales. Riparian vegetation composition was strongly correlated to landscape‐scale filters including elevation, precipitation and temperature. Watershed‐scale filters such as grazing and reach filters indicative of fluvial setting were also correlated to vegetation composition, often differentiating communities with similar landscape settings. We identified 10 distinct vegetation communities. Forested communities occurred at higher elevation, moderate gradient reaches with high mean annual precipitation. Shrub–forb systems corresponded to fluvial and watershed disturbances and occurred within climates that could preclude forest establishment. Meadows corresponded to high water tables and/or high grazing activity. Variance partitioning showed that landscape‐scale filters explained the most variance within vegetation communities. Global change will alter many of the environmental filters that drive vegetation. Vegetation change may occur rapidly if local filters (e.g. fluvial process) change rapidly or may occur more slowly if larger‐order filters (e.g. climate) change slowly and without influencing local hydrogeomorphic filters. By identifying filter–vegetation relationships at large spatial scales, hypotheses can be constructed on how riparian vegetation communities may change under future environmental conditions. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

The role of riparian vegetation and woody debris in the development of macroinvertebrate assemblages in streams

Riparian vegetation development and macroinvertebrate assemblages were studied in 16 streams formed between 35 and 230 years ago, following glacial recession in Glacier Bay National Park, southeast Alaska. Riparian vegetation established most rapidly in streams where flow variation in downstream reaches was buffered by a lake. Riparian vegetation development was positively correlated with lower bank stability, but was independent of stream age. Roots and branches of riparian vegetation trailing into streams (trailing riparian habitat—TRH) were shown to be an important habitat for a number of macroinvertebrate taxa. In young and unstable streams, TRH was colonized mainly by Plecoptera whereas in more stable lake‐influenced streams Simuliidae dominated. Significant coarse woody debris (CWD) accumulations were not observed until after approximately 130 years of stream development had occurred when certain channel features, such as gravel bars, were stabilized by dead wood. Where dead wood was present, opportunistic wood taxa were abundant, even in the younger streams. However, a xylophagous species, Polypedilum fallax, was not recorded until streams were over 100 years old. Two‐way indicator species analysis (TWINSPAN) using presence/absence of macroinvertebrate taxa on TRH, initially divided streams into lake and non‐lake systems, but subsequent divisions were consistent with differences in stream age. TWINSPAN of macroinvertebrate assemblages on dead wood again highlighted differences in stream age. Canonical correspondence analysis indicated that bed stability and stream age were the most important environmental variables influencing macroinvertebrate distribution on TRH. Trailing riparian habitat was most abundant in moderately unstable streams where it facilitates invertebrate colonization. CWD contributes markedly to channel stabilization, provides habitat for invertebrate xylophages, and confers additional habitat complexity. Maximum levels of CWD are predicted to occur in non‐lake streams after approximately 300 years, but at least a further 100 years will be required in stable streams below lakes where dead wood entrainment is not enhanced by flooding, channel migration and bank undercutting. A conceptual model summarizing the role of TRH and CWD on stream development in Glacier Bay is presented. Copyright © 2005 John Wiley & Sons, Ltd.     

STREAM RESTORATION AND CRIBWALL PERFORMANCE: A CASE STUDY OF CRIBWALL MONITORING IN SOUTHERN ONTARIO

Stream restoration focusing on adaptable natural and inert material use has been implemented through soil bioengineering designs aimed at the stabilization of urbanized streams. Within each design application materials such as large wood, sediment fill and vegetation must be suited to diverse settings. This paper discusses the application of cribwalls as soil bioengineering designs found in two Southern Ontario watersheds and the criteria that influence their performance. Field measurements of cribwall cuttings, sediment sampling, erosion pin monitoring, and computer‐generated stream power analysis are used to compare design performance at several sites. It is determined that the technical specifications of the design and site characteristics such as stream power distribution, sediment, and channel planform are equally involved in long‐term streambank stability. The results indicate that cribwalls with dense cutting growth perform well on streambanks that offer a greater amount of soil cohesion, nutrients, and infiltration in the mid and upper sections of the bank. In streams with moderate channel slopes and stream power distribution that is above the watershed mean, streams with well‐developed floodplains, sinuous channel planforms, and low bank height ratios perform better than those that are confined, straightened, and have greater bank height ratios. Throughout the comparison of several cribwall sites, the implication of this work is to demonstrate how to assess the fitness of similar soil bioengineering designs for application to diverse stream settings and to further validate their significance in stream restoration as designs that are multifunctional. Copyright © 2013 John Wiley & Sons, Ltd.     

Spatial distribution and geomorphic condition of fish habitat in streams: an analysis using hydraulic modelling and geostatistics

Reach‐scale physical habitat assessment scores are increasingly used to make decisions about management. We characterized the spatial distribution of hydraulic habitat characteristics at the reach and sub‐reach scales for four fish species using detailed two‐dimensional hydraulic models and spatial analysis techniques (semi‐variogram analyses). We next explored whether these hydraulic characteristics were correlated with commonly used reach‐scale geomorphic assessment (RGA) scores, rapid habitat assessment (RHA) scores, or indices of fish biodiversity and abundance. River2D was used to calculate weighted usable areas (WUAs) at median flows, Q₅₀, for six Vermont streams using modelled velocity, depth estimates, channel bed data and habitat suitability curves for blacknose dace (Rhinichthys atratulus), brown trout (Salmo trutta), common shiner (Notropis cornutus) and white sucker (Catostomus commersoni) at both the adult and spawn stages. All stream reaches exhibited different spatial distributions of WUA ranging from uniform distribution of patches of high WUA to irregular distribution of more isolated patches. Streams with discontinuous, distinct patches of high score WUA had lower fish biotic integrity measured with the State of Vermont's Mixed Water Index of Biotic Integrity (MWIBI) than streams with a more uniform distribution of high WUA. In fact, the distribution of usable habitats may be a determining factor for fish communities. A relationship between predicted WUAs averaged at the reach scale and RGA or RHA scores was not found. Future research is needed to identify the appropriate spatial scales to capture the connections between usable patches of stream channel habitat. Copyright © 2008 John Wiley & Sons, Ltd.