Stream Bank Vegetation Research Articles

Long-term Channel Geometry Adjustments for Reference Streams in the North Carolina Piedmont

The evaluation of reference streams can inform stream restoration designs, ecological function targets, hydraulic and sediment transport regimes, and project success criteria. Reference streams are often assumed to be in a state of quasi-equilibrium, with a hydraulic geometry representing a long-term average of a channel’s form that has developed under relatively constant morphological boundary conditions. However, more rapid changes in boundary conditions, such as water or sediment discharge, bed material size, or streambank vegetation, can result in accelerated changes to channel morphology and the development of new hydraulic geometry relationships . The goal of this study was to evaluate the morphologic equilibrium of reference streams by quantifying their long-term adjustments in riffle cross-section dimensions (i.e., width, mean depth, and cross-sectional area) and discharge. Eighteen reference streams in the Piedmont of North Carolina, United States, originally assessed in 2007, were resurveyed in 2017 and 2018 (hereinafter referred to as 2018). The adjustment in riffle channel geometry was quantified and evaluated by analyzing existing boundary conditions and changes in watershed land cover and precipitation patterns. Hydraulic geometry relationships (i.e., geometry parameters and discharge versus drainage area) from 2007 and 2018 were nearly identical and no statistically significant differences were detected in bankfull discharge, cross-sectional area, width, or mean depth. Inspection of individual sites revealed bankfull cross-sectional area adjusted by 0% to 19% at most sites, however 4 urbanizing sites adjusted by more than 25%. The adjustments in discharge and area from 2007 to 2018 were significantly correlated with impervious cover, indicating channel geometry adjustments are likely the result of changes in discharge that occur as a result of changes in watershed conditions and land cover. Changes in precipitation did not appear to be drivers of adjustment, as patterns were similar during the 10.5-year period preceding each field survey in 2007 and 2018. These data were used to update the regional curve relationships, and other summary morphological data compiled can be used to help guide future stream restoration designs. The geometry adjustments and percent erosion reported for the more stable reference streams can serve as a gauge for evaluating the degree of change in channel geometry measured at both degraded and restored streams.

Are natural floods accelerators for streambank vegetation development in floodplain restoration?

AbstractRiverbanks are very dynamic habitats for riparian vegetation strongly influenced by fluvial and geomorphic processes. This habitat type was severely reduced in the past by river straightening and bank stabilisation. Restoration and establishment of new floodplain streams promote this habitat, but a directed succession to later stages was observed many times. Our study aimed to analyse whether the often observed directed succession of the streambank vegetation after restoration implementation could be reversed by a natural flood along a newly created floodplain stream. We investigated the effects of a natural flood in 2013 and different prerestoration conditions on species development in the riparian zone. Vegetation was studied along 12 transects in four different sections from 2011 to 2014. Species composition differed strongly between the sections. Species richness was lowest in a newly dug steep section with high morphological dynamics and highest on wider flat streambanks. Changes during the years reflecting different hydrological events varied between sections. The high natural flood in 2013 reduced the cover of the herb layer and increased bare ground, which led in most sections to a loss of nontarget species. Total target species richness did not change due to the natural flood, while target species showed a high turnover rate. In the following year, however, the flood‐induced development of species composition, in general, was reversed. Natural floods changed abiotic and biotic conditions along the streambank, but they did not accelerate ecological restoration towards predefined target ecosystems. However, they were necessary to preserve the needed dynamic vegetation changes and species turnover to hinder the succession to later stages dominated by a few species. Our study shows that riparian vegetation near the streambank can be monitored most effectively in cross‐profile transects, both in the long‐term and event‐related.

The role of increasing riverbank vegetation density on flow dynamics across an asymmetrical channel

Over the last two decades, the role of vegetation in the environmental and ecological restoration of surface water bodies has received much attention. In this context, the momentum exchange between the flow through the main channel and the riparian zone is a key mechanism. The primary goal of this study is to investigate the role of bank vegetation density on flow dynamics across the whole channel. This experimental study presents the major findings from a series of flow measurements across a channel having a sloping bank with vegetation at varying densities. The experiments are conducted under the same, uniform flow and fixed bed conditions, for a range of six linear and rectilinear arrangements of incremental streambank vegetation densities. A set of ten velocity profiles is obtained across the test cross-section of the channel, including the riverbank, for each vegetation density. These flow measurements are analyzed to derive roughness coefficients, which are related to the bulk flow velocities through the main channel and the riverbank and discuss the redistribution of flow velocities. An approximate doubling for the estimates of time-averaged boundary shear stress at the main channel, is observed for the case of no to dense vegetation, which enable further discussing implications for the stability of bed surface material. It is found that the vegetation arrangement, in addition to vegetation density, can have a strong impact in modifying the mean flow velocity at the main channel, for low riparian densities (φ < 0.6%).HighlightsFlow dynamics are measured across the whole channel, including the vegetated riverbank.As stem density increases, mean flow velocity in the main channel increases while mean flow at the riverbank decreases.The arrangement of riparian vegetation can be as important as that of the density, in modifying the mean flow field of the main channel, for low riparian densities.Bed shear stresses at the main channel are estimated to increase with riverbank vegetation, reducing the stability of the stream’s bed surface.

Artemisia estesii (Asteraceae), a new diploid species of the Artemisia ludoviciana complex in the Pacific Northwest (U.S.A.)

The new species described here, Artemisia estesii, belongs to the Artemisia ludoviciana Nutt. species’ group in the Pacific Northwest. It was shown by J.R. Estes (1968a, 1969) to be a diploid member of an otherwise polyploid hybrid complex, with most of its related species and subspecies occurring at the tetraploid and hexaploid levels. Artemisia estesii is recognized by its underground and emergent, over-wintering, basal shoots, which are homologs of the elongate, underground rhizomes found in other herbaceous Artemisia species. Its regularly lobed leaf blades, with usually a broad rachis, differ from subspecies of A. ludoviciana in eastern Oregon. It occupies a narrow zone of streambank vegetation along the central Deschutes River and extends eastward along the lower Crooked River. Disjunct populations are known from Wheeler County and Lake County.

Is the Sosiani River Healthy? Investigating the Relationship between Water Quality Indicators and Macroinvertebrate Assemblages in the Sosiani River

The health of rivers is of great concern to governments and communities worldwide due to their important ecological functions. Numerous studies have established that water quality indicators have a positive effect on river health. However, only a few studies have examined equatorial rivers, and, to date, there has been no study on the Sosiani River in Kenya. As such, this study explored the health of the Sosiani River by considering how its aquatic macroinvertebrate assemblages were affected by various water quality parameters. The research considered whether there was a relationship between water quality indicators and macroinvertebrate assemblages in the Sosiani River. This knowledge is of paramount importance to the communities and decision makers of the Sosiani catchment, and Kenya as a whole, since there is need to understand the relationship between the water quality indicators and the health of the river in order to allocate resources for its rehabilitation and maintenance. This study examined 10 sites, nine being “test” sites and one a “reference” site. The study established a significant relationship between water quality parameters and macroinvertebrate assemblages. The sites with natural riparian zone vegetation conditions were found to have more Ephemeroptera, Plecoptera, and Trichoptera macroinvertebrates when compared to those without or with exotic vegetation. In terms of absolute numbers of surface aquatic macroinvertebrates, sites characterised by dense stream bank vegetation had more macroinvertebrates than those characterised by forest with eroded, bare stream banks. From the study, it was therefore concluded that Sosiani River is healthier at head waters where there was natural forests compared to downstream where there was plantations, intensive farming and urban area. The study recommends that more detailed studies classify macroinvertebrates to gunus level and include microinvertebrates, since this may give a more accurate assessment of the river’s health. The study further recommends that identification keys for East African macroinvertebrates be developed.

Some Medicinal Plant Species of Asamagbe Stream Bank Vegetation, Forestry Research Institute of Nigeria, Ibadan

A survey was conducted along Asamagbe stream bank of the Forestry Research Institute of Nigeria, Ibadan in order to assess the numerous medicinal plants present in the area. 98 species in 92 genera and 49 families were identified. Trees were most common (44%) among the plant life forms identified. Interviews were conducted with local people who reported medicinal uses. These uses are also supported from previous studies. We conclude that it is important to adopt conservation practices for sustainable plant use within and outside the study area in-view of the ecological function of the stream bank and the local therapeutic value of these plant resources.

Habitat Requirements of the Endangered California Freshwater Shrimp (Syncaris Pacifica) in Lagunitas and Olema Creeks, Marin County, California, USA

This study was conducted to better understand the habitat requirements and environmental limiting factors of Syncaris pacifica, the California freshwater shrimp. This federally listed endangered species is native to perennial lowland streams in a few watersheds in northern California. Field sampling occurred in Lagunitas and Olema creeks at seasonal intervals from February 2003 to November 2004. Ten glides, five pools, and five riffles served as fixed sampling reaches, with eight glides, four pools, and four riffles located in Lagunitas Creek and the remainder in Olema Creek. A total of 1773 S. pacifica was counted during this study, all of which were captured along vegetated banks in Lagunitas Creek. Syncaris pacifica was most numerous in glides (64%), then in pools (31%), and lastly in riffles (5%). According to logistic regression analysis, S. pacifica was mostly associated with submerged portions of streambank vegetation (especially overhanging vegetation such as ferns and blackberries, emergent vegetation such as sedge and brooklime, and fine roots associated with water hemlock, willow, sedge, and blackberries) along with low water current velocity and a sandy substrate. These seemingly favorable habitat conditions for S. pacifica were present in glides and pools in Lagunitas Creek, but not in Olema Creek.

Grazed Riparian Management and Stream Channel Response in Southeastern Minnesota (USA) Streams

The U.S. Department of Agriculture-Natural Resources Conservation Service has recommended domestic cattle grazing exclusion from riparian corridors for decades. This recommendation was based on a belief that domestic cattle grazing would typically destroy stream bank vegetation and in-channel habitat. Continuous grazing (CG) has caused adverse environmental damage, but along cohesive-sediment stream banks of disturbed catchments in southeastern Minnesota, short-duration grazing (SDG), a rotational grazing system, may offer a better riparian management practice than CG. Over 30 physical and biological metrics were gathered at 26 sites to evaluate differences between SDG, CG, and nongrazed sites (NG). Ordinations produced with nonmetric multidimensional scaling (NMS) indicated a gradient with a benthic macroinvertebrate index of biotic integrity (IBI) and riparian site management; low IBI scores associated with CG sites and higher IBI scores associated with NG sites. Nongrazed sites were associated with reduced soil compaction and higher bank stability, as measured by the Pfankuch stability index; whereas CG sites were associated with increased soil compaction and lower bank stability, SDG sites were intermediate. Bedrock geology influenced NMS results: sites with carbonate derived cobble were associated with more stable channels and higher IBI scores. Though current riparian grazing practices in southeastern Minnesota present pollution problems, short duration grazing could reduce sediment pollution if managed in an environmentally sustainable fashion that considers stream channel response.

Responses to Riparian Restoration in the Spring Creek Watershed, Central Pennsylvania

Abstract Riparian treatments, consisting of 3‐ to 4‐m buffer strips, stream bank stabilization, and rock‐lined stream crossings, were installed in two streams with livestock grazing to reduce sediment loading and stream bank erosion. Cedar Run and Slab Cabin Run, the treatment streams, and Spring Creek, an adjacent reference stream without riparian grazing, were monitored prior to (1991–1992) and 3–5 years after (2001–2003) riparian buffer installation to assess channel morphology, stream substrate composition, suspended sediments, and macroinvertebrate communities. Few changes were found in channel widths and depths, but channel‐structuring flow events were rare in the drought period after restoration. Stream bank vegetation increased from 50% or less to 100% in nearly all formerly grazed riparian buffers. The proportion of fine sediments in stream substrates decreased in Cedar Run but not in Slab Cabin Run. After riparian treatments, suspended sediments during base flow and storm flow decreased 47–87% in both streams. Macroinvertebrate diversity did not improve after restoration in either treated stream. Relative to Spring Creek, macroinvertebrate densities increased in both treated streams by the end of the posttreatment sampling period. Despite drought conditions that may have altered physical and biological effects of riparian treatments, goals of the riparian restoration to minimize erosion and sedimentation were met. A relatively narrow grass buffer along 2.4 km of each stream was effective in improving water quality, stream substrates, and some biological metrics.

Riparian buffers mitigate effects of pine plantation logging on New Zealand streams1. Riparian vegetation structure, stream geomorphology and periphyton

Influences of the riparian zone vegetation characteristics on bank erosion, stream geomorphology, irradiance and periphyton were examined at 28 sites in the Whangapoua area of the Coromandel Peninsula, North Island, New Zealand. Riparian buffers were defined as areas alongside streams that were not managed for production forestry, and which contained native indigenous vegetation or mixed indigenous and introduced flora. Five forest and riparian zone types were selected: (i) harvested pine plantation with a clearcut to stream edge, (ii) harvested pine plantation with a vegetated riparian buffer, (iii) mature pre-harvest pine plantation with a riparian buffer dominated by native vegetation, (iv) mature pre-harvest pine plantation with a riparian zone of plantation pines and a native vegetation understorey, and (v) mature native forest reference sites. Up to eight replicates were selected for each management regime. Species composition and canopy cover were measured from bounded plots, and stream bank vegetation was recorded separately. Bank erosion was measured along the full length of each study reach, and stream water width and bankfull width were measured at ten transects within each study reach. Stream and bank lighting were measured using a canopy analyser. Periphyton standing crop was measured as Chlorophyll a and ash-free dry weight. Although channel width increased with catchment area for all of the study reaches, bank erosion and channel widths were greater at harvested sites where plantation pines occurred at the stream edge (i.e. within the riparian zone), than other forest and riparian treatments. Stream lighting was heavily influenced by the presence of riparian vegetation as well as stream size for these small to moderate size streams. Mature radiata pine in riparian areas of pre-harvest sites provided shading which was similar but less variable than that recorded in the native reference sites. Mature pine forest may be shading out the taller growing native broadleaved canopy, and thus creating a denser 5–11.9 m height class, reducing light penetration. The lack of native species >12 m in height is likely to be due to the length of time which native conifers and hardwoods take to develop as these are the species which normally dominate the greater than 12 m height class. Periphyton biomass was lowest at pre-harvest sites with native riparian buffers present and greatest at clearcut harvested sites with clearcut riparian zones. This work shows that riparian vegetation composition and maturity can influence the physical characteristics of afforested and harvested New Zealand streams.

Riparian buffers mitigate effects of pine plantation logging on New Zealand streams: 1. Riparian vegetation structure, stream geomorphology and periphyton

Abstract Influences of the riparian zone vegetation characteristics on bank erosion, stream geomorphology, irradiance and periphyton were examined at 28 sites in the Whangapoua area of the Coromandel Peninsula, North Island, New Zealand. Riparian buffers were defined as areas alongside streams that were not managed for production forestry, and which contained native indigenous vegetation or mixed indigenous and introduced flora. Five forest and riparian zone types were selected: (i) harvested pine plantation with a clearcut to stream edge, (ii) harvested pine plantation with a vegetated riparian buffer, (iii) mature pre-harvest pine plantation with a riparian buffer dominated by native vegetation, (iv) mature pre-harvest pine plantation with a riparian zone of plantation pines and a native vegetation understorey, and (v) mature native forest reference sites. Up to eight replicates were selected for each management regime. Species composition and canopy cover were measured from bounded plots, and stream bank vegetation was recorded separately. Bank erosion was measured along the full length of each study reach, and stream water width and bankfull width were measured at ten transects within each study reach. Stream and bank lighting were measured using a canopy analyser. Periphyton standing crop was measured as Chlorophyll a and ash-free dry weight. Although channel width increased with catchment area for all of the study reaches, bank erosion and channel widths were greater at harvested sites where plantation pines occurred at the stream edge (i.e. within the riparian zone), than other forest and riparian treatments. Stream lighting was heavily influenced by the presence of riparian vegetation as well as stream size for these small to moderate size streams. Mature radiata pine in riparian areas of pre-harvest sites provided shading which was similar but less variable than that recorded in the native reference sites. Mature pine forest may be shading out the taller growing native broadleaved canopy, and thus creating a denser 5–11.9 m height class, reducing light penetration. The lack of native species >12 m in height is likely to be due to the length of time which native conifers and hardwoods take to develop as these are the species which normally dominate the greater than 12 m height class. Periphyton biomass was lowest at pre-harvest sites with native riparian buffers present and greatest at clearcut harvested sites with clearcut riparian zones. This work shows that riparian vegetation composition and maturity can influence the physical characteristics of afforested and harvested New Zealand streams.

Plan could protect Klamath fish and agriculture

Klamath River basin fish and farms in Oregon and California both could be protected, according to a 21 October report by the U.S. National Research Council. The report, by a committee of the Council's Board on Environmental Studies and Toxicology, calls for protecting three imperiled fish species through the removal of some dams which serve as migration obstacles, habitat improvement, and measures to stem the loss of stream bank vegetation and to lower the summer water temperatures in tributaries.The committee found that maintaining water levels and flows higher than those of recent past years would not likely lead to the recovery of two endangered sucker species and a genetically distinct population of Coho salmon that is threatened.

Influence of bank vegetation on channel morphology in rural and urban watersheds

Stream-bank vegetation significantly influences the morphology of streams in the Piedmont region of the United States. We surveyed the morphology of 26 paired stream reaches in southeastern Pennsylvania, northern Maryland, and Delaware. One member of each pair has a forested riparian zone, whereas the other has a riparian zone composed pri marily of grass. The paired reaches are nearly contiguous, so all significant channel-forming variables except riparian vegetation are held constant. The extent of urban development of the watersheds upstream of the paired reaches also varies considerably, allowing us to determine the combined influence of riparian vegetation and urbanization on channel morphology. Statistical analyses indicate that (1) channels with forested riparian zones are wider than channels with nonforested riparian zones, (2) channels in urbanized watersheds are wider than channels in nonurbanized watersheds, and (3) the effect of riparian vegetation is independent of the level of urbanization.

Lag in Stream Channel Adjustment to Livestock Exclosure, White Mountains, California

AbstractLivestock have been excluded from riparian zones along many streams in western North America in an effort to restore aquatic and riparian habitat degraded by livestock grazing. Within these exclosures, channel adjustment to elimination of grazing pressure may lag behind plant recovery because of the time required to deposit sediment along the vegetated banks of the stream channel. Moreover, unless grazing is eliminated from the watershed, the channel within the exclosure must still accommodate increased runoff and sediment loads from upstream. This hydrologic regime may prevent a return to predisturbance channel morphology. Cross sections of the North Fork Cottonwood Creek in the White Mountains of California showed no significant difference in channel width within and downstream of a 24‐year‐old exclosure, despite a lush growth of stream bank vegetation that gives the impression of a narrower channel within the exclosure.

Effects of Electric Transmission Rights-of-Way on Trout in Forested Headwater Streams in New York

Fifteen crossings of headwater streams by electric transmission rights-of-way (ROWS) in forested areas of New York State were studied to determine the effects of ROWS on habitat and populations of brook trout Salvelinus fontinalis and rainbow trout Oncorhynchus mykiss. Trout habitat and abundance in ROWS were compared with those in adjacent upstream reaches within the forest. The stream reaches in the ROWS were exposed to more light, had more dense streambank vegetation, were deeper and narrower, and had greater area composed of pools; water temperature was not significantly greater. Trout were more abundant in reaches within ROWS. The greater mean depth and more numerous pools within ROWS were believed to have caused higher densities of trout.

The origins of acid runoff in a hillslope during storm events

Abstract At the Svartberget Research Catchment in northern Sweden, stream pH had risen to 5.7 after a period of dry summer weather in 1987 before it dropped to below 4.4 during three ensuing storm events. To clarify the relationship between flow pathways and episodic acidity, the sources of storm runoff and its acidity in one of the catchment hillslopes were investigated. Hydrological considerations locate the origins of the runoff within the upper four decimeters of the soil in a swath some 50m wide along the stream. Groundwater remained alkaline throughout the episodes. Increases in the total organic carbon content of runoff appeared to play a central role in the stream pH decline. The episode's acidity and distinctive chemical ‘fingerprint’ originated in the runoff's passage through the organic-rich forest mor and/or streambank vegetation. Results from a column-leaching experiment supported this hypothesis. Such localized origins of runoff and especially of acidity may be of significance when calculating the rate at which acid episodes in other catchments respond to changes in acid deposition. A better understanding of the interaction between runoff and organic material is needed to determine whether the acidity at Svartberget is natural or if it has been affected by atmospheric inputs of anthropogenic origin.

Modelling nitrate removal by riparian vegetation in a springfed stream: The influence of land-use practices

Abstract Downstream nutrient flux has been modelled in a second-order springfed stream in New Zealand where the stream banks have been protected by the establishment of fenced riparian strips. This has allowed the development of an aquatic stream bank vegetation which assists in the removal of dissolved nitrogen from the stream water. The model comprises a coupled system for first-order, non-linear partial differential equations to incorporate the feedback effects of nitrogen uptake and release as the water moves downstream. The most sensitive parameters in the model were shown to be the growth and mortality constants for the aquatic vegetation. Analysis of varied farming practices on nutrient uptake by the riparian vegetation shows that winter grazing of the system is disadvantageous to nutrient uptake but that grazing at rates 2 to 3 times the regional average can be sustained during summer months without adversely affecting uptake. Decreasing nutrient mass flows at the springs either by altering concentration or discharge would greatly reduce nutrient export when below defined threshold values, and increases in mass flows above these values would increase export proportionately. Nutrient uptake was found to be proportional to concentration only at low flows.

Grazing Effects on Stream Habitat and Fishes: Research Design Considerations

A 4-year study of a montane stream from which cattle grazing had been excluded for 10 years indicated that stream bank vegetation and stability were markedly improved and that stream substrate fines were somewhat reduced, but it indicated that fish populations were unaffected. Shortcomings of this case history study are common to past similarly designed studies of grazing effects on fishes and their habitats. Three major deficiencies in research design are (1) lack of pretreatment data, (2) improper consideration of fishery management principles, and (3) linear positioning of treatments along a stream. Future research on riparian grazing effects must address these factors in addition to designs of long-term (10+ years) ecosystem (watershed) studies.

Effects of thirty-five years of afforestation with Pinus radiata on the composition of mesic mountain fynbos near Stellenbosch

The fynbos vegetation of Biesievlei, Jonkershoek, was surveyed and described in 1945. In 1948 the catchment was afforested with Pinus radiata . This paper presents results of a reassessment of the vegetation in 1984 using the same methods that were used in 1945. Afforestation has reduced the cover of the vegetation (excluding P. radiata ) from 75% to 20%. The total number of species was reduced by 58% from 298 to 126. At least 190 species found in 1945 were not found in 1984, and at least 18 species were added to the list. The mean plant density was reduced from 260 to 78 plants m − 2 . Only stream bank vegetation, comprising mainly large-leaved sprouting shrubs, persisted in a relatively unmodified state. Away from the stream, annuals, geophytes and hemicryptophytes were dominant. Dominant species in the pre-afforestation flora were not resilient to afforestation. Serotinous Proteaceae, woody small-leaved sprouting and myrmecochorous shrubs and large-leaved sprouting shrubs have been virtually eliminated. Certain groups may re-establish after clearfelling, but others, notably various groups of shrubs may have been permanently eliminated. The implications for weed control in conservation areas are discussed.

Material and Site Controls of Stream Bank Vegetation

ABSTRACT THIS article describes three specific conditions which limit the estabhshment of permanent vegetative cover for many stream banks in northern Mississippi. Critical conditions are imposed either directly or indirectly by the properties and failure mechanisms of the bank materials. These materials are primarily outcrops of valley-fill units that were deposited during the Holocene Epoch. Material properties and failure mechanisms are relatively consistent within units but differ between units. Two of these specific conditions involve bank height and angle. For a given material, these site conditions indirectly hmit vegetation by controlling mass failure frequencies. Bank instabiUty occurred when bank heights and/or angles were greater than critical, resulting in a loss of vegetative cover. The third condition was imposed by distinctive properties of the early-Holocene massive silt unit. This material is dense and has a well-developed polygonal structure that causes near-vertical bank angles. Outcrops of this material in the channel bank are typically barren of vegetation, but many such outcrops have been relatively stable except where channel entrenchment has exposed excessively weak toe materials. These results establish that bed and bank-toe stability is a prerequisite to the development of permanent vegetation on channel banks for this study area in northern Mississippi. Additionally, these results illustrate the usefulness of classifying channel bed and bank materials as units of the valley-fill system.