little river revisited thirty five years after hack and goodlett abstract in possibly the first detailed study to relate geomorphology vegetation and hydrology at a watershed scale hack and goodlett 1960 documented variation in the eastern forest with topograhic positions of cove side slope and nose runoff identified as convergent parallel or divergent supported forest types respectively of northern hardwood oak and yellow pine the study conducted in the little river basin of northwestern virginia also described effects on landforms and vegetation of a catastrophic flood that occurred in june 1949 field investigations conducted nearly 4 decades later review selected parts of the study by hack and goodlett 1960 replicate data provide a basis to evaluate interpretations of hack and goodlett to document geomorphic change within the little river basin since the 1949 flood and to identify vegetation change in uplands and bottomlands results suggest that change to hillslope landforms has been minor since 1949 but that changes have occurred to the little river and its tributaries seemingly during flow events of 1952 1955 and 1985 change in areal extent of forest types was not detected change in the relative abundances of dominant species may have resulted from 20th century fire suppression

geomorphic and vegetative characteristics along three northern virginia streams geometry sediment and woody vegetation data were collected from bottomland geomorphic surfaces at valley sections along three gaged perennial streams of northern virginia the basins of the streams differ widely in topography and physiography mean discharges vary from 0 196 to 323 m3 per sec prevalent surfaces identified were the depositional bar the active channel shelf the flood plain and terraces the stages corresponding to active channel shelf levels were equivalent to flow durations of 5 to 13 stages corresponding to flood plain levels were equivalent to discharges with 1 4 to 2 0 yr recurrence intervals the discharge data and statistical tests of geomorphicsurface sediment and vegetative data suggest that the various alluvial features are formed and maintained by hydraulically controlled sorting processes analysis of woody plant and geomorphic data shows that each surface supports characteristic species some of which are nearly unique to a surface tests of sediment type with species distribution showed lower correlation than that of geomorphic surface with species it is inferred that plant distributions largely are controlled by flow frequency and intensity and that plants may help to identify geomorphic levels and potential for flood damage

can the sedimentological and morphological structure of rivers be used to predict characteristics of riparian seed banks abstract seeds are transported by flowing water along with sediment and organic matter and form seed banks within the fluvial landforms or geomorphic units of river systems fluvial processes commonly result in observable gradients in sediment characteristics with elevation above the channel bed this study aims to investigate spatial variability in seed bank characteristics that may be attributed to fluvial processes we compared the extent to which four riparian seed bank characteristics abundance species richness seed mass and seed shape are correlated with 1 fluvially influenced gradients in sediment character percentage of organic matter organic median particle size d50 percentage of fine particles fines and the combined percentage of sand and gravel sand gravel and 2 three geomorphic unit types that form with increasing elevation above the channel bed bars benches and the floodplain seed bank abundance and species richness were weakly yet significantly correlated with sediment gradients significantly increasing with increasing fines and decreasing sand gravel seed bank species richness also significantly increased with increasing organic and decreasing d50 conversely seed abundance was highly variable and relationships between sediment qualities and seed mass and shape were nonexistent we suggest that hydrological factors such as inundation frequency operating most clearly at the geomorphic unit scale ultimately drive spatial variability in riparian seed bank characteristics by 1 directly influencing seed inputs and losses from seed banks via erosion and deposition which is complicated by species specific differences in seed morphology and 2 indirectly influencing seed inputs and losses by mediating seed germination and mortality and the establishment success of plants through impacts on sediment moisture and organic matter content further complexity is added by nonfluvial seed inputs from established vegetation the net result of these influences tends toward decreasing potential for seed losses and increasing potential for seed inputs associated with the reduction in inundation frequency observed from bars to the floodplain for those assessing the potential of the seed bank as a seed source for revegetation sediment sampling for seed bank assays targeted at organic flood debris or fine organic rich sediments such as those typically associated with benches and the floodplain should elicit useful estimations of seed bank composition

woody vegetation and channel morphogenesis in low gradient gravel bed streams in the ozark plateaus missouri and arkansas woody vegetation affects channel morphogenesis in ozark streams of missouri and arkansas by increasing local roughness increasing bank strength providing sedimentation sites and creating obstructions to flow variations in physiographic controls on channel morphology result in systematic changes in vegetation patterns and geomorphic functions with increasing drainage basin area in upstream reaches streams have abundant bedrock control and bank heights that typically are less than or equal to the rooting depth of trees in downstream reaches where valleys are wider and alluvial banks are higher vegetation has different geomorphic functions at drainage areas of greater than 100 200 km2 ozarks streams are characterized by longitudinally juxtaposed reaches of high and low lateral channel migration rates referred to as disturbance reaches and stable reaches respectively whereas stable reaches can develop stable forested floodplains if they are not farmed disturbance reaches are characterized by dynamic vegetation communities that interact with erosion and deposition processes disturbance reaches can be subdivided into low gradient and high gradient longitudinal zones low energy zones are characterized by incremental unidirectional lateral channel migration and deposition of gravel and sand bars the bars are characterized by prominent bands of woody vegetation and ridge and swale topography channel monitoring data indicate that densely vegetated bands of woody vegetation formed depositional sites during bedload transporting events the same floods caused up to 20 m of erosion of adjacent cutbanks scoured non vegetated areas between vegetation bands and increased thalweg depth and definition in high energy or riffle zones channel movement is dominantly by avulsion in these zones vegetation creates areas of erosional resistance that become temporary islands as the channel avulses around or through them woody vegetation on islands creates steep root defended banks that contribute to narrow channels with high velocities calculation of hydraulic roughness from density and average diameter of woody vegetation groups of different ages indicates that flow resistance provided by vegetation decreases systematically with group age mainly through decreasing stem density if all other factors remain constant the stabilizing effect of a group of woody vegetation on a gravel bar decreases with vegetation age

riparian vegetation and fluvial geomorphic processes abstract riparian vegetation and fluvial geomorphic processes and landforms are intimately connected parts of the bottomland landscape relations among vegetation processes and landforms are described here for representative streams of four areas of the united states high gradient streams of the humid east coastal plain streams great plains streams and stream channels of the southwestern united states vegetation patterns suggest that species distributions in the humid east are largely controlled by frequency duration and intensity of floods along channelized streams vegetation distribution is largely controlled by variation in fluvial geomorphic processes cycles of degradation and aggradation in response to increases in channel gradient associated with channelization similarly riparian vegetation of great plains streams may be controlled by fluxes in sediment deposition and erosion along braided streams patterns of riparian vegetation in semi arid regions may be most closely related to patterns of water availability unlike most other streams in more humid environments channel equilibrium conditions control stability of the coincident fluvial landform and attendant vegetation pattern throughout the continent in most situations riparian vegetation patterns are indicative of specific landforms and thus of ambient hydrogeomorphic conditions

interactions between semi natural vegetation and hydrogeomorphological processes abstract within britain lowland heaths and floodplain forests are rapidly disappearing from the landscape this paper considers the hydrogeomorphological significance of these two types of semi natural vegetation cover using research results gathered from a drainage basin in the new forest southern england whilst heathland vegetation communities are closely adjusted to the soil water hydrological regime floodplain forests have a distinctive and significant influence on the geomorphology of river channels both of these types of interaction are not only of hydrogeomorphological interest but provide an essential foundation for the effective management and restoration of catchments and rivers containing these types of vegetation cover

the headward extent of fluvial landforms and associated vegetation on massanutten mountain virginia variation in fluvial landforms and associated vegetation in the headward upstream direction has received little study and the controlling factors are not well understood the relations among channel gradient basin area stream order and the headward extent of fluvial landforms and vegetation was studied in 18 small basins and larger nearby stream reaches in the massanutten mountain area northern shenandoah valley virginia low order streams were traversed to their basin heads notice was made of the point or region of the disappearance of fluvial landforms indicator species were used to confirm landform identification the studied landforms include the channel bar channel shelf floodplain and terraces basin geomorphic characteristics were determined from topographic and geologic maps and ground surveys results suggest that gradient is the most important factor controlling the development of fluvial landforms floodplains have not developed along stream reaches where average channel gradients exceed 0 15 channel shelves and associated vegetation occur farther upstream than floodplains

hydrologic inferences from tree ring studies on the hawkesbury river sydney australia abstract introduced salix trees in australian alluvial environments can be used to make a number of hydrologic inferences dendrochronological studies along the hawkesbury river near windsor suggest that the salix growth form and annual growth ring variability are closely associated with the local hydrologic regime detailed analyses of 33 trees showed that tree growth is suppressed close to water and increases with height above mean low stage levels because of the decreasing influence of flooding alluvial levels contain discrete vegetation patterns and growth characteristics that are not explained by variations in soil and climate growth of salix in thickets on low in channel benches is flood limited with fitted exponential growth curves having positive or zero slopes the high in channel bench contains vegetation influenced by flooding but growing according to classical exponential decay functions trees on floodplain levees show full canopy development and the most rapid growth because of fertile soils the high availability of water and limited influence of floods overtopping levee tops elevation and tree growth relations are used to develop a relation between growth and flood frequency this is applicable to catchments of similar size soil type and climate analyses of tree form and root distribution indicated that dendrochronological techniques may be used to determine the minimum land surface age and rates of accretion around the tree bole in alluvial areas of southeastern australia

floodplain dynamics of a wandering river dendrochronology of the morice river british columbia canada dendrochronological techniques are used to develop a history of flood occurrence and relative stage for the middle section of the morice river based on flood scars bank undercutting dates and tree establishment dates on fluvial features the morice river is the major tributary of the bulkley river skeena river system northwest british columbia canada reach 2 of the morice river drainage area 3499 km2 is forested and little disturbed by human activity it is presently a wandering multiple channel river and shows evidence of frequent channel changes which have reworked most of the floodplain several times in the last 180 years airphoto analysis and dendrochronology demonstrate that many channels show evidence of two or more periods of activity reoccupation and re excavation of pre existing channel segments is more frequent than development of new channels thirty one significant floods over the past 105 years were detected through dendrochronology of flood scarred trees on the morice river flood scars are predominantly caused by flood transported logs abundant log transport results in damage to channel margin trees during events only slightly above bankfull discharge the record of flood scars on channel margin trees and establishment dates of forest stands on abandoned channels and surfaces show that the morice river has maintained its present regimen for the past 115 years during the neoglacial the morice river was more active than in recent times and its channels occupied twice the present area tree establishment dates show that neoglacial surfaces and channels of the morice river were abandoned during the 1820 s the modern floodplain configuration was assumed by 1870

potential controls of alluvial bench deposition and erosion in southern piedmont streams alabama usa abstract benches are bank attached channel deposits occurring at an elevation between the channel bed and top of banks their occurrence in a variety of geologic and hydrologic settings has led to confusion about the mechanisms driving their formation which in turn contributes to difficulty identifying the active floodplain bankfull stage and the determination of environmental flows in some rivers hydrodynamic modeling software river 2d in combination with sediment particle size analysis and total station topographic surveys was used to simulate flow conditions needed to erode and deposit the d84 d50 and d15 particle sizes of concave and lateral benches in two rivers talladega and hillabee creeks in alabama results suggest that bench erosion requires flows at least 150 larger than benchfull stage at the talladega site while the hillabee site experienced erosion at all discharges meeting and exceeding benchfull flow stage likely owing to its overall smaller sediment particle sizes at both sites the presence of vegetation increased the bench area subjected to deposition but somewhat counterintuitively also helped influence the location of erosion by limiting flow vectors in contrast with previous research findings the occurrence of reverse flow was neither sustained nor widespread at either site these findings provide new insight into alluvial benches suggest that the study benches are relatively stable features under the prevailing hydrologic regime and that in some temperate climate settings such as the southern piedmont localized hydraulic controls on bench formation can be superseded in importance by hydrologic flow regime even in the case of concave benches and where flow regulation is not a factor

spatial patterns of hydrology geomorphology and vegetation on the floodplain of the amazon river in brazil from a remote sensing perspective abstract the spatial heterogeneity of hydrology and vegetation during high water periods in geomorphically distinct reaches of the amazon river in brazil was determined based on semivariance statistics the spatial statistics were derived from three classified landsat thematic mapper images representing upstream to downstream geomorphic characteristics in the upstream river reach scroll bar topography on the floodplain tends to channelize floodwater into floodplain drainage channels thus reducing the diversity of water types by reducing opportunities for mixing of flooding river water with locally derived floodplain water the highest diversity of vegetation types is along floodplain drainage channels while the rest of the floodplain has a more homogeneous cover in the middle reach of the river the diversity of wetland classes as measured by semivariance is higher than both upstream and downstream perhaps because of exposure to more water types and landforms the diversity of water types is high because flooding river water flows onto the floodplain as diffuse non channelized overbank flow as well as through drainage channels the non channelized overbank flow readily mixes with locally derived floodplain water floodplain landforms available for colonization by vegetation include scroll bars swales lake shores lake deltas and floodplain drainage channels in the downstream reach where the floodplain is wide relatively flat and covered with huge lakes the floodplain supports a moderately heterogeneous mix of vegetation communities where landforms are similar the spatial distribution of the vegetation is similar to that of the middle reach of the river in the downstream reach flooded forest comprised only 37 of the wetland vegetation in contrast in both the upstream and middle reaches over 70 of the wetland vegetation was flooded forest agricultural clearing of the floodplain is more common in downstream reaches and may account for the smaller percent of floodplain forest cover

bankfull hydraulic geometry the role of in channel vegetation and downstream declining discharges in the anabranching and distributary channels of the gwydir distributive fluvial system southeastern australia abstract australian rivers frequently exhibit long periods of low or no flow trees and shrubs that grow on the channel bed and discharges that decline downstream four channels of the gwydir distributive fluvial system gwydir and mehi rivers carole and moomin creeks greatly contrast the hydraulic geometry of most other rivers particularly in the way they respond to changes in discharge downstream data describing 167 cross sections across all four streams are assembled into standard exponential bivariate hydraulic geometry plots with the relationships shown to exist outside the range of previously investigated downstream changes i e in contrast to the commonly obtained exponents for width b depth f and velocity m of 0 5 0 4 and 0 1 respectively comparatively low exponents for width b 0 0 4 and high values for velocity m 0 26 0 42 reflect the importance of slope in accommodating changes in discharge in sharp contrast with nearly all previous hydraulic geometry investigations where discharge increases downstream and slope decreases in the gwydir system slope declines in sympathy with discharge resulting in a marked downstream decline in stream power the presence of in channel vegetation is also argued to be a highly significant influence on the downstream hydraulic geometry of these streams because these streams are frequently dry trees grow in abundance on the bed appearing to displace the flow laterally and causing the channels to widen and shallow downstream an adjustment that contrasts the high mud content of the boundary the result is a very different hydraulic geometry in this anabranching distributary system to that commonly described for other types of river

a calcium aluminum rich inclusion from the essebi cm2 chondrite evidence for captured spinel hibonite spherules and for an ultra refractory rimming sequence abstract an unusual refractory inclusion was discovered in the essebi cm2 chondrite the inclusion has high concentrations of refractory lithophile and siderophile elements with strong enrichments of the most refractory elements lu sc hf in one part of the inclusion the inclusion consists of a melilite rich core partially surrounded by a very refractory rim which in turn is covered by a mantle enriched in si al fe mn cl and s melilite compositions vary from ak 10 26 in the core to ak 0 12 in the rim the core contains several complex framboids consisting of spinel fassaite or spinel hibonite these framboids are probably spherules of the types reported from murchison and were possibly captured by the molten inclusion before it solidified these findings may indicate a genetic link between framboids in cai s and the spinel rich spherules in murchison the rim sequence consists of the following five layers from inside to outside 1 1 hibonite spinel melilite 2 2 hibonite perovskite spinel melilite melilite in this layer is altered to sodalite nepheline calcite 3 3 a hibonite corundum solid solution 4 4 a spinel corundum solid solution as much as 0 1 mole fraction al 2 67 o 4 5 5 sc rich fassaite as much as 6 2 wt sc 2 o 3 spinel al 2 o 3 solid solution al rich diopside pt rich metal crystals occur only in the rim some of these metal crystals contain minor amounts of zr and hf indicating that they formed under reducing conditions the bulk mineral chemistry and texture of the essebi inclusion indicates a complex history involving capture of solid spinel and spinel hibonite spherules similar to the murchison type by a refractory melt droplet solidification of the droplet without obliteration of the spherule textures transportation of the composite object to hotter regions of the solar nebula where the very refractory rim condensed alteration of melilite to sodalite nepheline minor calcite and finally burial in the essebi parent body the cl s bearing mantle probably formed by reactions between the inclusion and liquid and gaseous phases in the parent body

large woody debris physical process and riparian forest development in montane river networks of the pacific northwest abstract we present a conceptual biogeomorphic model of riparian forest development in montane river networks the role of physical process in driving the structure composition and spatial distribution of riparian forests is examined we classify the drainage network into disturbance process based segments including 1 debris flow and avalanche channels 2 fluvial and debris flow channels and 3 fluvial channels riparian forests are shown to be significant in the development of channel morphology through the stabilization of active floodplains and as sources of large woody debris olwd lwd is operationally defined as wood 0 1 m diameter and 1 m length lwd plays a key role in the development of montane riparian forests lwd deposited in the active channel and floodplain provides sites for vegetation colonization forest island growth and coalescence and forest floodplain development riparian forest patterns parallel the distribution of hillslope and fluvial processes through the network riparian forest structure composition and spatial distribution through the network are driven by the major disturbance processes including 1 avalanches 2 debris flows and 3 flooding riparian forest patterns also reflect the action of lwd in the organization and development of forested floodplains in gravel bedded montane river networks the focus of our examples are montane river networks of the pacific northwest usa

delivery of upper basin sediment to the lower neuse river north carolina u s a extensive storage of upper basin piedmont sediment and apparent low sediment supply to streams in lower basin coastal plain areas generates questions as to the source of alluvium in lower reaches of rivers of the u s atlantic drainage this was investigated on the neuse river north carolina using a mineralogical indicator of sediment source areas the utility of mica flakes for discriminating between piedmont and non piedmont sources of sediment in the lower coastal plain reaches of the neuse was established on the basis of an examination of the u s national soils database and of 26 soil surveys of the north carolina coastal plain from the neuse river estuary to 48 km upstream there are no mica flakes in floodplain soils or in river bank and channel shelf sediments mica flakes become more common upstream this suggests that a very small proportion of the sediment eroded in the piedmont portion of the watershed is delivered to the river mouth the small amounts which presumably do reach the lower coastal plain are so diluted by coastal plain derived alluvium that no piedmont origin can be discerned this demonstrates a dominantly coastal plain source and underscores the importance of storage and discontinuous transport in fluvial sediment systems more importantly results suggest that upper and lower basin sediment dynamics are not only non linearly related but may be virtually decoupled

vegetative impacts on hydraulics and sediment processes across the fluvial system summary vegetation creates a complicated system of feedbacks and linkages across the fluvial system that is realized through river planform shape interactions occur among flow hydraulics sediment deposition and erosion and plant morphology density and biomechanics interest in the interactions and feedback loops between vegetation and the fluvial system has grown extensively in the past few years this interest is partially driven by the popularity of stream restoration activities worldwide that include re vegetation of stream banks and formation of an ecosystem that is intended to encourage the growth of aquatic macrophytes we present a review of the research into the interactions and dependencies between vegetation and the fluvial system to identify hydraulic and sediment dynamics that are consistent around vegetation located in the channel on channel banks and over the floodplain we illustrate process commonalities operating across spatial locations within the fluvial system and highlight some of the current research opportunities and challenges to encourage research collaborations between those working in areas of the fluvial system traditionally viewed as disparate

preservation of in situ arborescent vegetation and fluvial bar construction in the burdekin river of north queensland australia abstract in sub humid parts of north queensland ne australia certain types of trees are well adapted to living in river bed habitats the bed of the tropical variable discharge upper burdekin river hosts a community dominated by the paperbark melaleuca argentea trees grow preferentially in flow parallel linear groves and engineer their own environment by deflecting currents building sand and gravel bars and stabising banks this is the first study to document in channel bar development resulting from vegetation growth rather than the reverse which has been inferred by previous workers in the burdekin river study site individual melaleuca range from seedlings to mature trees over 100 years old these trees survive regular partial to total submergence and impact damage during wet season runoff events often reaching over 20 000 m3 s 1 at peak discharge partly by adopting structural and growth modifications these modifications include a reclined downstream trailing habit multiple stemmed form modified crown with weeping foliage development of thick spongy bark root regeneration and group strategies notably development of flow parallel linear groves following death in situ remains of trees are preserved within the mainly coarse sand to gravel channel fill either as reclined stems trunks stripped of branches and foliage or as more upright trunks snapped at a height of typically 1 2 m above base both with roots the morphological adapations and styles of preservations of in situ vegetation within the burdekin river are considered distinctive of variable discharge rivers and may be useful in the identification of facies formed in such environments in the rock record particularly when associated with bar development

recent and historic sediment dynamics along difficult run a suburban virginia piedmont stream abstract suspended sediment is one of the major concerns regarding the quality of water entering the chesapeake bay some of the highest suspended sediment concentrations occur on piedmont streams including difficult run a tributary of the potomac river draining urban and suburban parts of northern virginia accurate information on catchment level sediment budgets is rare and difficult to determine further the sediment trapping portion of sediment budget represents an important ecosystem service that profoundly affects downstream water quality our objectives with special reference to human alterations to the landscape include the documentation and estimation of floodplain sediment trapping present and historic and bank erosion along an urbanized piedmont stream the construction of a preliminary sediment balance and the estimation of legacy sediment and recent development impacts we used white feldspar markers to measure floodplain sedimentation rates and steel pins to measure erosion rates on floodplains and banks respectively additional data were collected for from legacy sediment thickness and characteristics mill pond impacts stream gaging station records topographic surveying and sediment density texture and organic content data were analyzed using gis and various statistical programs results are interpreted relative to stream equilibrium affected by both post colonial bottomland sedimentation legacy and modern watershed hardening associated with urbanization six floodplain channel sites from high to low in the watershed were selected for intensive study bank erosion ranges from 0 to 470 kg m y and floodplain sedimentation ranges from 18 to 1369 kg m y m refers to meters of stream reach upstream reaches are net erosional while downstream reaches have a distinctly net depositional flux providing a watershed sediment balance of 2184 kg m y trapped within the system the amounts of both deposition and erosion are large and suggest nonequilibrium channel conditions both peak discharge and number of peaks above base have substantially increased since the mid 1960s when urbanization of the watershed began deposition patterns are most closely correlated with channel gradient sinuosity and channel width floodplain width for recent and historic periods the substantial amounts of fine grained sediment deposited on the floodplain over the past two centuries or so do not appear to be closely related to historic mill pond presence or location the floodplain continues to provide the critical ecosystem service of sediment trapping in the face of multiple human alterations trends in sediment deposition erosion may react rapidly to land use practices within the watershed and offer a valuable barometer of the effects of management actions

patterns of floodplain sediment deposition along the regulated lower roanoke river north carolina annual decadal centennial scales abstract the lower roanoke river on the coastal plain of north carolina is not embayed and maintains a floodplain that is among the largest on the mid atlantic coast this floodplain has been impacted by substantial aggradation in response to upstream colonial and post colonial agriculture between the mid eighteenth and mid nineteenth centuries additionally since the mid twentieth century stream flow has been regulated by a series of high dams we used artificial markers clay pads tree ring dendrogeomorphic techniques and pollen analyses to document sedimentation rates amounts over short intermediate and long term temporal scales respectively these analyses occurred along 58 transects at 378 stations throughout the lower river floodplain from near the fall line to the albemarle sound present sediment deposition rates ranged from 0 5 to 3 4 mm y and 0 3 to 5 9 mm y from clay pad and dendrogeomorphic analyses respectively deposition rates systematically increased from upstream high banks and floodplain to downstream low banks reaches except the lowest reaches conversely legacy sediment deposition a d 1725 to 1850 ranged from 5 to about 40 mm y downstream to upstream respectively and is apparently responsible for high banks upstream and large wide levees along some of the middle stream reaches dam operations have selectively reduced levee deposition while facilitating continued backswamp deposition a gis based model predicts 453 000 mg of sediment is trapped annually on the floodplain and that little watershed derived sediment reaches the albemarle sound nearly all sediment in transport and deposited is derived from the channel bed and banks legacy deposits sources and regulated discharges affect most aspects of present fluvial sedimentation dynamics the lower river reflects complex relaxation conditions following both major human alterations yet continues to provide the ecosystem service of sediment trapping