incision due to gravel mining modeling a case study from the gallego river spain abstract historical information on river degradation was used in a case study on the gallego river a tributary of the ebro river in northeastern spain the gallego drains about 4000 km 2 of the southern slopes of the pyrenees good channel surveys since the 1940s allowed a comparison of longitudinal bed profiles over time over this period about 1 million m 3 of gravel was mined according to the archival records the volume of alluvium lost due to incision in the same period was 2 million m 3 this imbalance is tentatively explained by a budget model based on a bedload equation and an algorithm to determine whether the effective bedload transport is controlled by the transport capacity or by the supply of sediment it appears that the incision process has changed the magnitude of the shear stresses on channel bed as the river became deeper the channel could accommodate higher discharges without overbank flooding the results obtained from a second model based on diffusion equation for the bed elevation compared well with the field data this model is based on the hypotheses of steady uniform flow regarding water and sediment conservation

architecture and evolution of a fjord head delta western vancouver island british columbia the architectural framework and holocene evolution of the zeballos fjord head delta on west central vancouver island was established through a multidisciplinary field based study the zeballos delta is a composite feature consisting of an elevated incised late pleistocene delta and an inset holocene delta graded to present sea level both deltas have a classic gilbert type tripartite architecture with nearly flat topset and bottomset units and an inclined foreset unit time domain electromagnetic tdem and ground penetrating radar gpr surveys borehole data and gravel pit exposures provided information on the internal form lithologies and substrate of both deltas both sets of deltaic deposits coarsen upward from silt in the bottomset unit to gravel in the topset unit the tdem survey revealed a highly irregular buried bedrock surface ranging from 20 m to 190 m in depth and it delineated saltwater intrusion into the deltaic sediments late quaternary sea level change at zeballos was inferred from delta morphology and the gpr survey the elevated late pleistocene delta was constructed when the sea was about 21 m higher relative to the land than it is today it was dissected when sea level fell rapidly as a result of glacio isostatic rebound relative sea level reached a position about 20 m below the present datum during the early holocene foreset beds that overlap and progressively climb in a seaward direction and topset beds that thicken to 26 m landward imply that the delta aggraded and prograded into zeballos inlet during the middle and late holocene transgression sea level may have risen above the present datum during the middle holocene creating a delta plain at about 4 m a s l remnants of this surface are preserved along the valley margins copyright 2004 john wiley sons ltd

late quaternary sea levels and crustal movements coastal british columbia late quaternary sea level fluctuations on the british columbia coast have been established from studies of terrestrial and marine sediments and landforms these studies indicate that the sea level history of mainland british columbia and eastern vancouver island is very different from that of the queen charlotte islands and western vancouver island specifically in the former areas there was a rapid rise of submerged coastal lowlands between about 13 000 and 10 000 years ago emergence culminated about 6000 9000 years ago depending on the locality when the sea relative to the land was 12 m or more lower than at present in some areas during middle and late holocene time relative sea level rose on the mainland coast and at least locally on eastern vancouver island resulting in inundation of coastal archaeological sites and low lying terrestrial vegetation tidal records and precise levelling suggest ongoing submergence of at least part of this region in contrast shorelines on the queen charlotte i

controls and limits on bedrock channel geometry 1 data on channel geometry in naturally incising bedrock rivers reveal variable relationships between channel width slope and erosion rate to explain the range of relationships between these parameters we propose an optimized channel geometry model the model reproduces previous theoretical and numerical modeling scaling relationships however to explain the field data the model must incorporate the effects of immobile sediment cover that reduces vertical incision efficiency adding sediment to a system for a given rate of base level fall both widens and steepens the channel we also find that a constant width to depth ratio is only valid for streams where the shear stress required for sediment transport is insignificant compared to the shear required to erode at the imposed base level fall our model offers an explanation of seemingly contradictory field observations of controls on channel width and shows that channel width fundamentally controls the erosive potential of a river especially when it carries a significant bed load

channel adjustments following two dam removals in wisconsin 1 we examined channel response following the removal of low head dams on two lowgradient fine to coarse grained rivers in southern wisconsin following removal channels eroded large quantities of fine sediment resulting in deposition 3 5 km downstream at one site baraboo river upstream changes were rapid and included bed degradation minimal bank erosion and sediment deposition on channel margins and new floodplain sand was transported through the former impoundment and temporarily deposited downstream at the second site koshkonong river head cut migration governed channel adjustments a deep narrow channel formed downstream of the headcut with negligible changes upstream of the head cut fluvial changes were summarized in a conceptual channel evolution model that highlighted 1 similarities between adjustments associated with dam removal and other events that lower channel base level and 2 the role of reservoir sediment characteristics particle size cohesion in controlling the rates and mechanisms of sediment movement and channel adjustment index terms 1815 hydrology erosion and sedimentation 1824 hydrology geomorphology 1625 1857 hydrology reservoirs surface keywords dams dam removal channel evolution model

migration of a coarse fluvial sediment pulse detected by hysteresis in bedload generated seismic waves a b s t r a c t seismic signals near rivers are partially composed of the elastic waves generated by bedload particles impacting the river bed in this study we explore the relationship between this seismic signal and river bedload transport by analyzing high frequency broadband seismic data from multiple stations along the chijiawan river in northern taiwan following the removal of a 13 m check dam this dam removal provides a natural experiment in which rapid and predictable changes in the river s profile occur which in turn enables independent constraints on spatial and temporal variation in bedload sediment transport we compare floods of similar magnitudes with and without bedload transport and find that the amplitude of seismic shaking produced at a given river stage changes over the course of a single storm when bedload transport is active hysteresis in the relationship between bedload transport and river stage is a well documented phenomenon with multiple known causes consequently previous studies have suggested that hysteresis observed in the seismic amplitude stage response is the signature of bedload transport field evidence and stream profile evolution in this study corroborate that interpretation we develop a metric for the normalized magnitude of seismic hysteresis during individual floods this metric appears to scale qualitatively with total bedload transport at each seismic station indicating a dominance of transport on the rising limbs of both storms we speculate that hysteresis at this site arises from time dependent evolution of the bed for example due to grain packing mobile armoring or the temporal lag between stage and bedform growth reveals along stream variations in hysteresis for each storm with a peak in hysteresis further downstream for the second event the pattern is consistent with a migrating sediment pulse that is a predicted consequence of the dam removal our results indicate that hysteresis in the relationship between seismic wave amplitude and river stage may track sediment transport

observations on delta forming processes in a fjord head delta british columbia canada abstract the bella coola delta is a laterally confined steep fronted fjord head delta in north bentinck arm in the pacific coast mountains of british columbia the principal controls on sedimentation are 1 the high sediment yield and bedload dominance of the bella coola river which reflect climatic conditions and high drainage basin relief 2 river mouth processes which are controlled by tidal stage and delta morphology and 3 delta front deformational processes which are related primarily to oversteepening in the upper delta front wave processes are of limited significance the large tidal range 3 9 m mean range 5 9 m large range changes the location of distributary outlets at high tide and high discharge frictional forces dominate and the effluent disperses as a plane jet over the delta plain at low tide and high discharge inertial frictional and buoyant forces are important and the effluent disperses over saline basin water subaqueous landslides and debris flows have produced a series of erosional chutes on the delta front

gpr in sediments advice on data collection basic processing and interpretation a good practice guide within sedimentological studies ground penetrating radar gpr is being used with increasing frequency because it yields images of the shallow subsurface that cannot be achieved by any other non destructive method the purpose of this paper is to provide an introduction to the collection processing and interpretation of gpr data so that future sedimentary studies can be improved with gpr equipment now being lightweight robust and portable proper data collection and survey design methods need to be followed in order to acquire high resolution subsurface digital data various factors are discussed including reflection profiling velocity soundings test surveys topography logistics data quality and extreme environments basic data processing and visualization are then reviewed followed by a discussion on gpr interpretation strategies including a background to radar stratigraphy for the sedimentary geologist or geomorphologist gpr offers unique data of the shallow subsurface including stratigraphy geometry architecture and structure

a 1 d morphodynamic model of postglacial valley incision chilliwack river is typical of many cordilleran valley river systems that have undergone dramatic holocene degradation of valley fills that built up over the course of pleistocene glaciation downstream controls on base level mainly blockage of valleys by glaciers led to aggradation of significant glaciofluvial and glaciolacustrine valley fills and fan deposits subsequently incised by fluvial action models of such large scale long term degradation present a number of important challenges since the evolution of model parameters such as the rate of bedload transport and grain size characteristics are governed by the nature of the deposit sediment sampling in the chilliwack valley reveals a complex sequence of very coarse to fine textural modes we present a 1 d numerical morphodynamic model for the river floodplain system tailored to conditions in the valley the model is adapted to dynamically adjust channel width to optimize sediment transporting capacity and to integrate relict valley fill material as the channel incises through valley deposits sensitivity to model parameters is studied using four principal criteria profile concavity rate of downstream grain size fining bed surface sand content and the timescale to equilibrium model results indicate that rates of abrasion and coarsening of the grain size distributions exert the strongest controls on all of the interrelated model performance criteria while there are a number of difficulties in satisfying all model criteria simultaneously results indicate that 1 d models of valley bottom sedimentary systems can provide a suitable framework for integrating results from sediment budget studies and chronologies of sediment evacuation established from dating

late quaternary sediments and geomorphic history of north central vancouver island materials from two glacial and two nonglacial intervals are identified on north central vancouver island british columbia the oldest pleistocene unit muchalat river drift consists of till and overlying glaciolacustrine silt it has been tentatively correlated with dashwood drift of the semiahmoo glaciation an overlying single exposure of mudflow sediment in the gold river valley contains wood dated at 40 900 2000 years bp within the time span of the olympia nonglacial interval the olympia nonglacial interval was characterized by a period of degradation in which olympia age sediments were deposited in transient sedimentary environments and subsequently eroded gold river drift includes gold river advance deposits gold river till and gold river late glacial deposits and was deposited during the fraser glaciation the fraser glaciation was well underway on north central vancouver island by 25 200 330 years bp during the fraser glaciation maximum which occurred after 20 600 330 years bp coast mountain ice flowed in a southwesterly direction across north central vancouver island overtopping all but the highest peaks of the vancouver island mountains deglaciation commenced prior to 12 930 160 years bp and the ice had probably disappeared before 9500 years ago during postglacial times rivers have dissected older quaternary sediments and bedrock up to at least 40 m macroflora data recorded in postglacial lacustrine sediments suggest that the hypsithermal interval commenced before 8300 70 years bp

hydraulic geometry of cohesive channels undergoing base level drop abstract this study extends earlier contributions on dynamic adjustments of fluvial channels to base level changes we have investigated an in situ response of self formed cohesive channels to a base level drop conditions analogous to a gradual change in uplift and or climate empirical hydraulic geometry equations for clayey cohesive natural streams are presented using data from eight channels draining perennial brackish springs and discharge into the dead sea investigation of downstream variations in gradient and stream power relations suggests existence of three distinct reaches in which channel adjustment to base level drop is shared inequitably among hydraulic geometry variables values of the flow velocity exponent m are low 0 11 m 0 24 the mid channel reach having the lowest exponent the depth exponent f has the lowest value f 0 3 for the uppermost channel reaches the rest having higher values f 0 4 the smallest width exponent b 0 35 characterizes the upper reaches these values and their spatial distribution exhibit a regular pattern we show that the lowermost channel reach adjusts by profile steepening and channel narrowing f b the prevailing mechanism in the mid channel reaches is lateral width adjustment cross sections transiently transforming toward equilibrium the uppermost reaches have wide and shallow channel cross sections because of series of bank collapses and resultant sediment aggradation bringing rise to decreased local gradient forcing further channel widening the results of this study not only allow inference about how cohesive channels regulate their geometry but also reveal the means by which hydraulic forces overcome substrate resistance adjusting slope and channel dimensions and as such have implication for reach scale channel morphology and models of stream power

small is beautiful upscaling from microscale laminar to natural turbulent rivers 1 the use of microscale experimental rivers with flow depths of the order of a few millimeters to investigate natural processes such as alluvial fans dynamics knickpoints migration and channel morphologies such as meandering and braiding has become increasingly popular in recent years this raises the need to address the issue of how to extrapolate results from the experimental microscale at which flow is laminar to the scale of natural turbulent rivers we address this question by performing measurements of average flow velocity and sediment transport in an experimental laminar river the average flow velocity is correctly predicted from the navier stokes equation solved for a steady uniform laminar flow laminar sediment transport is found to be consistent with the law of meyer peter and muller 1948 commonly used to describe sediment transport in natural turbulent rivers we also show that surface tension is important only if the microscale river width is on the order of or smaller than the capillary length these results allow us to demonstrate that the evolution of longitudinal bed profiles of turbulent and laminar rivers are governed by identical dimensionless equations and therefore follow the same dynamics differences of time and length scales at work in experimental and natural rivers are mainly encoded in the expression of two parameters a diffusion coefficient and a threshold slope on the basis of this analysis we derive a set of equations allowing us to rescale bed elevation downstream distance time and uplift rate from an experimental microscale river to the field scale finally we show how this set of equations can be used to rescale these same parameters in the case of a temporally varying discharge

a demonstration of the importance of bedload transport for fluvial bedrock erosion and knickpoint propagation we provide field evidence for the role of bedload in driving fluvial incision and knickpoint propagation using aerial photographs field surveys and hydrological data we constrain the incision history of a bedrock gorge 1200 m long and up to 20 m deep cut by da an river in western taiwan this reach of the river experienced 10 m of uplift during the 1999 chi chi earthquake for five years following the earthquake bedload was prevented from entering the uplift zone the knickpoint was static and little incision took place bedload transport across the uplift zone resumed in 2004 initiating extremely rapid incision with 620 m of knickpoint propagation and up to 20 m of downcutting by 2008 this change highlights the relative inefficiency of suspended sediment and the dominant role of bedload as a tool for fluvial erosion and knickpoint propagation once bedload tools became available knickpoint propagation was influenced by geological structure lithology and drainage organization in particular a change in dip of the sandstone beds at the site caused a decrease of knickpoint propagation velocity copyright 2012 john wiley sons ltd

channel evolution after dam removal in a poorly sorted sediment mixture experiments and numerical model dam removal is commonly used for river restoration however there are still some uncertainties associated with dam removal mainly related to the sediment transport rates released downstream from the deposit that had previously filled the impoundment this research studies the physical response to dam removal in the antecedent deposit by answering the following questions a how does an initial channel excavated into the deposit evolve and b what is the time distribution of the material released during the early stages of the process these goals are achieved by an experimental campaign using a poorly sorted mixture of sediment in the antecedent deposit the research shows that for the given conditions of our experiments the rate at which the sediment is released depends on the height of the removed dam the water discharge and the maximum potential volume of sediment to be eroded this investigation provides new insights of the width evolution when the sediment is composed of a poorly sorted mixture this evolution is linked to the bed degradation rates channel narrows during a rapid incisional phase and subsequently widens when bed degradation rates decrease channel width changes propagate upstream as a convection like perturbation associated with a kinematic wave starting at the location of the antecedent dam these features are modeled through a new numerical model accounting for mixtures more specifically a set of equations has been derived for the variation of bed elevation channel bottom width and bed grain size distribution which when solved numerically describe the observed channel processes

ground penetrating radar used to assess aggregate in catastrophic flood deposits northeast alberta canada coarse grained aggregate deposited by a catastrophic flood located north of fort mcmurray alberta was examined using ground penetrating radar gpr and lithostratigraphic logging techniques gpr transects were acquired from an upper scoured zone of flood deposits sedimentary structures cross beds and plane beds within the coarse sand and gravel and determinations of depth to bedrock sediment thickness of the aggregate were recognized in the gpr profiles by their varying dielectric properties fine grained conductive underlying oil sand till or glaciolacustrine sediment silt and clay attenuated the radar signal the sedimentary structures mapped from the gpr transects were confirmed in adjacent trench exposures we suggest that gpr is an efficient methodology for determining volumes of aggregate reserves thicknesses of aggregate deposits and mapping sedimentary structures of high energy fluvial sediments key words aggregate ground penetrating radar alberta spillway

from river to shelf anatomy of a high frequency depositional sequence the late pleistocene to holocene tiber depositional sequence the late pleistocene holocene tiber delta succession represents the most recent and one of the best preserved high frequency low rank depositional sequences developed along the latium continental margin of the italian peninsula several previous studies have established a robust data set from which it has been possible to describe the stratigraphic architecture of the entire tiber depositional sequence from the landward to seaward sectors and over a distance of 60 km the tiber depositional sequence shows many characteristics found in other late pleistocene to holocene deltaic and coastal successions of the mediterranean area the stratigraphic architecture of the tiber depositional sequence is controlled mainly by glacioeustasy although factors such as tectonic uplift volcanism and subsidence exert an influence at a local scale the resulting depositional model allowed discussion of some important points such as 1 the genesis of the tiber mixed bedrock alluvial valley extending from the coastal plain to the innermost portion of the shelf recording i multiple episodes of incision during relative sea level fall and ii a downstream increase of depth and width of the valley during the base level fall and the subsequent base level rise 2 the different physical expression of the tiber depositional sequence boundary from landward to seaward and its diachronous and composite character 3 the maximum depth reached by the tiber early lowstand delta at the end of the sea level fall is estimated at ca 90 m below the present sea level and not at 120 m as suggested by previous works 4 the backward position of the tiber late lowstand delta relative to the deposit of early lowstand 5 the change of the channel pattern and of the stacking pattern of fluvial deposits within the lowstand systems tract transgressive systems tract and highstand systems tract all of these features indicate that the late pleistocene holocene tiber delta succession even if deposited in a short period of time from a geological point of view represents the result of the close interaction among many autogenic and allogenic factors however global eustatic variations and sediment supply under the control of climatic changes can be considered the main factors responsible for the stratigraphic architecture of this sedimentary succession which has been heavily modified by human activity only in the last 3000 years

detection of subsurface brines freshwater bodies and the interface configuration in between by the time domain electromagnetic method in the dead sea rift israel high radon fluxes in the seismically active dead sea rift seem to be affected by the hydrological system and the different salinities of groundwater bodies involved the time domain electromagnetic tdem method was employed to delineate those different bodies and the configuration of the interfaces between them the present hydrological system and the related brines and interfaces are controlled by the dead sea base level presently at 408 m below msl tdem measurements detect low resistivity 1 ohm m units representing brines and the interface between them as well as the overlying fresher water bodies in addition high resistivity freshwater units are also detected underlying the brines related herein to a multiple hydrological system low resistivity brines detected above the present base level are interpreted herein as yet unflushed ones which correspond to a former higher base level higher sequences below historical sixteenth century base levels are already devoid of brines which gives an indication as to the rate of flushing

channel width response to differential uplift 1 the role of channel width and slope adjustments to differential uplift in rivers within actively deforming terrains remains contentious here high resolution topographic surveying of formerly antecedent outwash channels demonstrates marked changes in channel width as a primary response to differential uplift for five late quaternary alluvial paleochannels crossing small folds along the active ostler fault zone of southern new zealand nearly continuous measurements of paleochannel width and concomitant incision reveal abrupt narrowing of widths toward minimum values at channel positions coincident with the initial uplift when the magnitude of differential uplift is sufficiently small narrowing alone permits these channels to remain antecedent in the context of a unit stream power model for fluvial erosion observed limits on the magnitude of channel narrowing suggest that above some threshold amount of differential uplift continued incision requires concomitant changes in channel gradient thus when crossing small growing folds alluvial rivers simply narrow their channels whereas larger folds that demand greater incision prompt an initial narrowing followed by channel steepening

bank erosion of legacy sediment at the transition from vertical to lateral stream incision streambank erosion is a primary source of suspended sediments in many waterways of the us atlantic piedmont this problem is exacerbated where banks are comprised of fine sediment produced by the intensive land use practices of early european settlers a stream in this region richland creek incises into banks comprised of three stratigraphic layers associated with historic land use pre european settlement early european agriculture and development and water powered milldam operation this study aims to identify the bank processes along a reach of richland creek that is eroding towards its pre disturbance elevation the volume of material that has eroded along this stream since the milldam breached was calculated by differencing a reconstructed surface of the pond bed and an aerial lidar digital terrain model dtm immediately downstream from the study reach the channel is floored by bedrock and immediately upstream the rate of channel erosion approximately doubled along the longitudinal profile of richland creek which indicate that the study reach spans the transition from a channel dominated by vertical incision in the upstream direction to horizontal widening in the downstream direction the combined hydrometeorological conditions and dominant processes causing reach scale cut bank erosion were investigated with analyses of stream stage precipitation and streambank volumetric and surfaces change that was measured during nine terrestrial lidar surveys in 2010 2012 the spatial variability of erosion during a simulated precipitation event was examined in a field based experiment erosion was greatest where mill pond sediment columns detached along vertical desiccation and horizontal seepage cracks this sediment accumulated on the bank toe throughout the study and was a source of readily entrained fine sediment contrary to the upper reaches where depositional accommodation space is more limited findings suggest that hotspots of sediment excavation progress upstream indicating that restoration efforts should focus upon stabilizing banks at these locations copyright 2015 john wiley sons ltd

ongoing research at the late middle pleistocene site of la polledrara di cecanibbio central italy with emphasis on human elephant relationships abstract the site of la polledrara di cecanibbio latium italy is related to deposits of the pg6 sequence middle pleistocene aurelia formation mis 10 and 9 the sediments are mainly volcaniclastic in composition and constitute the filling of incised valleys mainly characterized by fluvial deposits at the base passing upward to fluvio lacustrine and palustrine deposits containing abundant fossil mammal remains and artifacts the arrangement of the specimens and taphonomic observations suggest that most of the transport of the bones occurred during flooding events followed by progressive swampy phases resulting in the formation of areas with stagnant and muddy waters where some elephants became trapped as indicated by remains in partial anatomical articulation recent excavations carried out at the site permit a better definition of the palaeoenvironmental reconstruction already partially outlined in previous publications in particular an area showing a close correlation between the skeleton of an elephant and human activity allows documentation and better understanding of some aspects of human elephant interaction probably mainly represented by scavenging activity

rapid post seismic landslide evacuation boosted by dynamic river width how rivers evacuate large landslide deposits is crucial for predicting post seismic hazards a 2d hydro sedimentary model demonstrates that a narrowing river channel increases sediment transport which reduces export time by orders of magnitude

river mouth processes in a fjord delta british columbia canada abstract the bella coola delta is a high energy coarse grained fjord delta situated in the coast mountains of british columbia river mouth processes are directly related to the large tidal range 3 9 m mean 5 9 m large which changes the location and nature of distributary mouths producing distinct high tide and low tide outlets frictional forces dominate at high tide as the effluent disperses through five dynamic zones producing a radial bar a friction model applies to this outlet during low tide frictional inertial and buoyant forces and an internal hydraulic jump control the development of six dynamic zones and a lunate middle ground bar a buoyant plane jet model qualitatively best approximates low tide outlet dynamics

holocene sea level change on the central west coast of vancouver island british columbia a new holocene relative sea level rsl curve is proposed for the central west coast of vancouver island based on topographic surveys of coastal landforms and the stratigraphy of coastal deposits six study sites are described on vargas island and esowista and ucluth peninsulas and 23 previously unpublished radiocarbon ages that constrain mean sea level msl position are presented a long term rise in rsl from an early holocene 7000 bp lowstand below 3 m asl is documented from dates on tree stumps in the intertidal zone and salt marsh peats and forest floor deposits buried by marine sands and gravels submergence culminated in a stillstand from 6000 to 4800 bp marked by the development of a strandline at 6 m asl msl 3 2 m asl a fall in rsl is documented by a strandline at 4 0 4 5 m asl which dates from 2700 to 2000 bp msl 2 0 m asl little is known of the dynamics of emergence between 4800 and 2700 bp or from 2000 bp to the present although the absence of strandlines below 4 m asl sugges

long term bed load transport rate based on aerial photo and ground penetrating radar surveys of fan delta growth coast mountains british columbia sequential aerial photography sonar bathymetry ground penetrating radar gpr and sediment sampling and analysis provide the basis for calculating the volumetric and mass rate of progradation of the delta of fitzsimmons creek a steep high energy debris flow dominated channel draining about 100 km2 of the southern coast mountains of british columbia fitzsimmons creek is typical of small mountain rivers in the region gpr imaging is used to define the pre depositional morphology of the receiving basin a technique that improves the accuracy of the volumetric survey the 52 year record 1947 1999 of progradation yielded an average annual volumetric transport rate of 1 00 0 16 104 m3 year 1 for bed load corresponding to a mass transport rate of 1 60 0 28 104 mg year 1 bed load yields are consistent with those obtained in hydrogeomorphically similar basins in the region and elsewhere decade based annual rates which vary from 0 64 0 11 104 to 2 85 0 38 104 mg year 1 provide poor estimates of the 52 year average indeed the 52 year record may also not be long enough to fully integrate the significant fluctuations in the sediment efflux from fitzsimmons creek the methodology proposed in this paper can be transferred to other comparable mountain environments worldwide

ground penetrating radar of northern lacustrine deltas ground penetrating radar gpr was used in several selected deltaic sedimentary environments to better understand subsurface stratigraphy and reconstruct former depositional environments the profiles provide high resolution continuous subsurface data on facies thickness and depths orientation of major sedimentary structures postdepositional failure planes and depth of peat deposits field experiments were carried out on six river deltas records from four of the deltas exhibit sedimentary facies a record from one delta shows a possible slump and records from another delta reveal the thickness and stratigraphic relationships of peat deposits the delta types are i sandy wave influenced ii sandy immature wave influenced steeper middle and lower shoreface iii sandy braided and iv gravelly fan foreset in areas of limited subsurface control stratigraphic logs from drill core cutbank exposure or geophysical logs radar profiles can provide big picture perspectives of the subsurface

experimental delta formation in crater lakes and implications for interpretation of martian deltas 1 the morphology of delta deposits in crater lakes on mars is indicative of upstream e g flow discharge and sediment properties and downstream e g basin characteristics parameters from which the hydrological conditions at the time of formation can be inferred to investigate the influences of these parameters on delta morphology we experimentally created deltas in crater shaped basins by feeding a range of constant flow discharges over a feeder channel of various sand textures we reproduced three categorically different types of deltas including most of the types that have been identified on mars our most striking observation is that water level behavior itself a unique function of flow discharge basin size and hypsometry and basin floor permeability can explain most delta morphologies observed on mars stepped retrograding deltas formed during water level rise prograding deltas formed during water level still stand and during water level fall deltas were partially destroyed by erosion on mars numerous retrograding and prograding deltas were preserved most of them without indications of channel incisions or other fluvial modification we conclude that the main difference between a single foreset prograding delta and a multiple foreset retrograding delta is the behavior of the water level in the basin these simple delta morphologies cannot be reconciled with long duration hydrological activity because that would imply crater lake fluctuations due to inherent complex water level histories along with complex sediment delivery histories our experiments and numerical verifications demonstrate that such deltas preferentially form during one aqueous event which parsimoniously argues for short duration hydrological activity

seismic cycles earthquakes landslides and sediment fluxes linking tectonics to surface processes using a reduced complexity model in tectonically active mountain ranges landslides triggered by earthquakes mobilise large volumes of sediment that affect river dynamics this sediment delivery can cause downstream changes in river geometry and transport capacity that affect the river efficiency to export this sediment out of the epicentre area the subsequent propagation of landslide deposits in the fluvial network has implications for the management of hazards downstream and for the long term evolution of topography over multiple seismic cycles a full understanding of the processes and time scales associated with the removal of landslide sediment by rivers following earthquakes however is still lacking here we propose a nested numerical approach to investigate the processes controlling the post seismic sediment evacuation at the mountain range scale informed by results from a reach scale model first we explore the river morphodynamic response to a landslide cascade at the reach scale using a 2d modelling approach the results are then used to describe empirically the evacuation of a landslide volume which avoids using a computationally extensive model in catchments which may have thousands of co seismic landslides second we propose a reduced complexity model to quantify evacuation times of earthquake triggered landslide clusters at the scale of a mountain range examining the hypothetical case of a mw 7 9 earthquake and its aftershocks occurring on the alpine fault new zealand our approach combines an empirical description of co seismic landslide clusters with the sediment export processes involved during the post seismic phase our results show that the inter seismic capacity of the mountain range to evacuate co seismic sediment is critical to assess the sediment budget of large earthquakes over one to several seismic cycles we show that sediment evacuation is controlled by two timescales 1 the transfer time of material from hillslopes to channels and 2 the evacuation time of the landslide deposits once it has reached the fluvial network in turn post seismic sediment evacuation can either be connectivity limited when sediment delivery along hillslopes is the main limiting process or transport limited when the transport by rivers is the limiting process despite high values of runoff we suggest that the southern alps of new zealand are likely to be in connectivity limited conditions for connection velocities 2 m yr 1 are sufficient to allow most of co seismic sediments to be mobilised and potentially exported out of the range within less than one seismic cycle because of the poorly constrained rate of sediment transfer along hillslopes our results potentially raise the issue of co seismic sediment accumulation within mountain ranges over several seismic cycles and of the imbalance between tectonic inputs and sediment export we therefore call for renewed observational efforts to better describe and quantify the physical processes responsible for the redistribution and mobilization of sediment from landslide scars and deposits

radiocarbon age constraints on rates of advance and retreat of the puget lobe of the cordilleran ice sheet during the last glaciation abstract calibrated radiocarbon dates of organic matter below and above till of the last fraser glaciation provide limiting ages that constrain the chronology and duration of the last advance retreat cycle of the puget lobe in the central and southeastern puget lowland seven dates for wood near the top of a thick proglacial delta have a weighted mean age of 17 420 90 cal yr b p which is the closest limiting age for arrival of the glacier near the latitude of seattle a time distance curve constructed along a flowline extending south from southwestern british columbia to the central puget lowland implies an average glacier advance rate of ca 135 m yr the glacier terminus reached its southernmost limit ca 16 950 yr ago and likely remained there for ca 100 yr in the vicinity of seattle where the glacier reached a maximum thickness of 1000 m ice covered the landscape for ca 1020 yr postglacial dates constraining the timing of ice retreat in the central lowland are as old as 16 420 cal yr b p and show that the terminus had retreated to the northern limit of the lowland within three to four centuries after the glacial maximum the average rate of retreat was about twice the rate of advance and was enhanced by rapid calving recession along flowline sectors where the glacier front crossed deep proglacial lakes

analogue modeling of transverse drainage mechanisms fifteen physical experiments on a stream table replicated four general mechanisms proposed to explain transverse drainage development namely antecedence superimposition overflow and piracy the experimental design encompassed multiple strategies to effectively replicate the different mechanisms these experiments roughly emulate natural fluvial processes including aggradation lateral erosion degradation knickpoint retreat ponding and overflow the experiments address landscape morphology and depositional field criteria associated with antecedence overflow and piracy antecedence experiments showed that defeat of streams by a tectonically growing structure could result from a combination of upstream ponding and diversion into a trunk drainage insufficiently fast retreating knickpoints and downstream deposition of eroded sediments piracy can result from stream aggradation until it overtops a low divide by headward erosion of a stream through a divide and by sapping processes for piracy driven by headward erosion asymmetrically sloped ridges allow the drainage divide across the ridge to retreat from headward erosion but a symmetric divide hinders the ability of a stream to retreat across the ridge apex aggradationally driven piracy is potentially hindered because the slope across the divide needs to be sufficiently steep compared to the uncaptured stream otherwise deposition occurs across the divide and a levee is formed which prevents capture for transverse drainages produced by overflow knickpoints retreat across the overflow outlet producing a high probability of downstream flooding a positive feedback develops where added discharge to the drainage from lake water increases erosion and knickpoint retreat further eroding and undermining the basin outlet and releasing even more lake water the result is rapid incision and dramatic flooding downstream of the bedrock high during lake outlet erosion two superimposition experiments were unsuccessful most of the field criteria for antecedence overflow and piracy were either directly replicated or implied based on observations during each experimental run

extreme rates of channel incision and shape evolution in response to a continuous rapid base level fall the dead sea israel abstract in nature opportunities are limited for recording the response to a rapid ongoing base level fall and for examining its effects on channel evolution during the process following a dramatic base level fall the natural laboratory area of the dead sea offers such an opportunity classical shape evolution models of incised channels describe the response to an impulse type base level drop after it became stabilized the dead sea delineates during its continuous level drop a different mode of adjustment from those previously conceptualized we have recorded the entrenchment rates of channels and their transient shape evolution at a station in real time i e during the ongoing base level fall this study represents the first attempt to apply integrated time series of high resolution dems change detection maps differential global position system measurements and field methods to monitor vertical and horizontal entrenchment rates as well as the evolution of the cross sectional shape of channels in response to a continuous and rapidly lowering base level mean vertical entrenchment rates are very high 0 4 0 8 m y and widening rates are even higher 2 1 24 m y elevation change detection maps demonstrate along banks a patchy pattern of channel entrenchment indicating the initial widening stage the incised channels have a trapezoidal gorge like cross sectional form i e they have developed beyond the initial stage of net vertical incision however neither advanced channel widening nor development of an inner floodplain has been observed we conclude that widening is yet ineffective in damping the vertical adjustment the continuous and rapid lowering of the dead sea level entraps the drainage systems in the vertical incision mode preventing the evolutionary progression toward a wide graded and stable geometry which has been conceptualized in existing models

seafloor morphology and sedimentary processes knight inlet british columbia seafloor morphology and sediment distribution in knight inlet are discussed as they relate to turbidity currents and associated gravity resedimentation phenomena the study is based on acoustic imagery high resolution seismic profiling echosounding sediment sampling and seabed monitoring seafloor morphology shows that while the upper part of knight inlet resembles other british columbia fjords it differs in that a great many channels emanate from fjord head deltas to coalesce ultimately into a few and finally one channel farther down inlet this is in contrast to the adjacent fjord buteinlet where only one channel emerges opposite each of the two fjord head rivers joining a short distance downslope to form a single incised channel in both fjords sand transporting turbidity currents are responsible for creating these extensive channel systems in knight inlet these channels are up to 40 m deep and up to 300 m wide continuing 41 km down fjord the upper fjord can be divided into four morphological zones which reflect not only the seabed character but also the flow characteristics of turbidity currents using a variety of theoretical techniques based on channel morphology coarsest grain sizes and bedform characteristics turbidity current dynamics were modelled for the seabed morphological zones turbidity current densities are estimated to range from about 1 024 g cm 3 in distal areas to a maximum of 1 048 g cm 3 in the proximal region of greatest erosion and highest velocities average flow velocities are as high as 7 00 m s 1 diminishing to less than 0 50 m s 1 at the terminus of the channel based on estimates of velocity and turbidity current density sediment fluxes were computed for various channel segments changes in flux rates clearly delineated areas of erosion and deposition and were well correlated with the morphological character of the channel and nearby seafloor estimates of turbidity current velocity based on bedform characteristics tend to be lower than those calculated from coarsest grain sizes and channel morphology preserved bedforms may reflect later waning phases of turbidity current flow whereas channel wall heights and coarsest grain size reflect maximum velocities a close relationship was found between turbidity current events as monitored by turbidity event detectors and river discharge peaks on the klinaklini river at the head of the inlet fluvial suspended matter concentrations associated with such floods are not believed to be sufficient to produce turbidity currents directly rather it is postulated that river mouth bars which accumulate during periods of low river flow are destroyed by floods and the coarse sediments along with flood related bedload are swept onto the steep delta front where they accumulate as temporary unstable sediment masses failing occasionally or continue directly downslope as debris flows turbidity currents

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

sediment transport and channel adjustments associated with dam removal field observations 1 this study documents changes in channel geometry bed level profile and bed grain size distribution and their relations with the sediment transport at the reach scale following the removal of a low head dam after the removal net sediment deposition occurred downstream of the dam and net erosion occurred in the reservoir but approximately less than 1 of the sediment stored in the reservoir was transported downstream no bank erosion was evident either upstream or downstream of the dam bed deposition and scouring in the reservoir accounted for a decrease in the bed slope of 30 the stations downstream of the dam had surface bed material sizes at least 40 finer than preremoval conditions however the sediment transport rates downstream of the dam were not significantly different from predam to postdam removal or from an upstream control overall the removal of the dam had only minor effects on the channel adjustment downstream of the dam a simple analysis linking transport to channel geometry explains this effect

natural streams and the legacy of water powered mills gravel bedded streams are thought to have a characteristic meandering form bordered by a self formed fine grained floodplain this ideal guides a multibillion dollar stream restoration industry we have mapped and dated many of the deposits along mid atlantic streams that formed the basis for this widely accepted model these data as well as historical maps and records show instead that before european settlement the streams were small anabranching channels within extensive vegetated wetlands that accumulated little sediment but stored substantial organic carbon subsequently 1 to 5 meters of slackwater sedimentation behind tens of thousands of 17th to 19th century milldams buried the presettlement wetlands with fine sediment these findings show that most floodplains along mid atlantic streams are actually fill terraces and historically incised channels are not natural archetypes for meandering streams

experiments on upstream migrating erosional narrowing and widening of an incisional channel caused by dam removal 1 the present paper reports on a laboratory investigation of the erosion of a deltaic front induced by the removal of a dam we built a laboratory model of a dam and observed both the sedimentation in the reservoir due to the downstream propagation of a delta front and the erosion of the delta front during dam removal including measurement of channel morphology and flow field the experiments provide a detailed view of a phenomenon that has not been described in detail to date erosional narrowing after the sudden removal of a dam the flow incises into the reservoir deposit first rapidly and then more slowly during the initial period of rapid incision the width of the channel can in some circumstances undergo rapid and substantial narrowing all the while incorporating sediment from its sidewalls as the rate of incision slows the channel first stops narrowing and then enters a phase of slow widening this pattern of narrowing followed by widening tends to propagate upstream the minimum channel width attained at a cross section however increases with upstream distance from the dam while the period of erosional narrowing is very short the incision is so intense that large amounts of sediment are delivered downstream in a short period of time the process thus has practical implications in regard to the strategy of dam removal undistorted froude similitude is used to scale the results up to field dimensions

experimental steep braided flow application to flooding risk on fans flooding processes occurring on alluvial fans are considerably different from those occurring along single thread rivers with well defined floodplains active erosion rapid sedimentation and the uncertainty in flow path make the prediction of flood evolution and extent difficult based on a large scale experiment this study investigates the long term evolution of the flow on a steep noncohesive sediment surface resembling a complex of merged alluvial fans the results are pertinent to the assessment of flooding hazard on alluvial fans at any given time the average flow occupancy was 21 of the surface however the flow was characterized by active channel switching and overflow processes the percentage of the surface remaining dry was found to decay harmonically with time a reworking time was defined as the time at which half of the surface that was initially dry remained dry whereas the other half was inundated at least once an empirical expression was developed in which reworking time is proportional to the average cross sectional area of flow and inversely proportional to the sediment supply

transient electromagnetic sounding for groundwater the feasibility of using the transient electromagnetic sounding ts or tdem method for groundwater exploration can be studied by means of numerical models as examples of its applicability to groundwater exploration we study four groundwater exploration problems 1 mapping of alluvial fill and gravel zones over bedrock 2 mapping of sand and gravel lenses in till 3 detection of salt or brackish water interfaces in freshwater aquifers and 4 determination of hydrostratigraphy these groundwater problems require determination of the depth to bedrock location of resistive high porosity zones associated with fresh water determination of formation resistivity to assess water quality and determination of lithology and geometry respectively the ts method is best suited for locating conductive targets and has very good vertical resolution unlike other sounding techniques where the receiver transmitter array must be expanded to sound more deeply the depth of investigation for the ts method is a

basin sedimentation and the growth of prograding deltas a theoretical model is developed for the infilling of a basin by the progradation of a delta the model simulates four mechanisms for the transfer of sediment from the land to the sea 1 bed load dumping along the delta front 2 hemipelagic sedimentation under the seaward flowing river plume 3 proximal slope bypassing by turbidity currents and 4 the combined effects of both short term wave and tidal action and long term creep and small slides downslope diffusion of the accreting sediment mass the general model is of relatively low precision useful for predicting basin infilling on time scales greater than a few hundred years the river plume portion of the model can predict sedimentation on time scales of less than a year and is designed to reflect the dynamics of a free two dimensional buoyant jet that transports a composite size population of suspended particles the general model allows the prediction of lithologies changing with time and space the model has been used to simulate infilling processes for knight and bute inlets two grabenlike fjord basins along the coast of british columbia model simulations of delta progradation over the last 10 000 years favorably predicted the modern seafloor bathymetry and sediment accumulation rates to within a factor of 2 of measured 210pb 137cs and sediment trap rates

imaging the subsurface stratigraphy in the ubehebe hydrovolcanic field death valley california using ground penetrating radar abstract ground penetrating radar gpr surveys were carried out to collect subsurface images of the basaltic base surge deposits in the ubehebe hydrovolcanic field death valley national park california antennae with frequencies of 50 100 and 200 mhz were used this technique allowed the collection of useful geologic data for example the lower stratigraphic boundary of the pyroclastic deposits can be imaged and their thickness can be estimated different radar responses were also obtained from base surge deposits and underlying sedimentary rocks which enable their recognition where no outcrops are available furthermore gpr data confirmed the presence of small eroded craters which are partially filled by alluvium in this case an unconformity between the overlying horizontally bedded alluvium and the underlying bowl shaped base surge deposits can be recognized within the crater and the thickness of the alluvium estimated common mid point cmp surveys suggested subsurface velocities of the electromagnetic waves in the upper part of these deposits between 0 095 0 1 m ns

alluvial gully erosion an example from the mitchell fluvial megafan queensland australia considerable attention has been focused on the role of gullies as a contributor to contemporary sediment loads of rivers in australia in southern australia rapid acceleration of hillslope gully erosion has been widely documented in the post european period last 200 years in the northern australian tropics however gully erosion processes operating along alluvial plains have not been well documented and can differ substantially from those gullies eroding into colluvium on hillslopes aerial reconnaissance surveys in 2004 along 13 500 km of the main stem rivers that drain into the gulf of carpentaria goc identified extensive areas of alluvial lands that have been impacted by a pervasive form of gully erosion more detailed remote sensing based mapping within the 31 000 km2 mitchell river fluvial megafan has identified that active gullying into alluvium occupies 0 4 129 km2 of the lower mitchell catchment these alluvial gullies are concentrated along main drainage channels and their scarp heights are highly correlated to the local relief between the floodplain and river thalweg while river incision into the megafan since the pleistocene has developed the relief potential for erosion other factors such as floodplain hydrology soil dispersibility and vegetation also influence the distribution of gullies in this paper we present a conceptual model of alluvial gullies and contend that they represent a distinct end member in the continuum of gully forms that have been described in the geomorphic literature an understanding of the processes driving this form of alluvial gullying can only be gained when they are differentiated from widely described colluvial hillslope gully models and theories we present evidence of type examples of alluvial gullying in the mitchell and through analysis of their distribution and morphology at different scales highlight some of the key mechanisms that are potentially initiating these features and driving their expansion copyright 2009 john wiley sons ltd

radar facies of paraglacial barrier systems coastal new england usa analysis of a large data base of ground penetrating radar gpr profiles from both natural and developed paraglacial barriers along the coast of new england has allowed identification of eight reflection configurations that characterize this type of mid to high latitude coastal environment bedrock anchor points yield primarily hyperbolic configurations whereas glacial anchor points and sediment source areas are characterized by chaotic parallel and tangential oblique configurations beaches and dunes produce predominantly sigmoidal oblique hummocky reflection free and bounding surface configurations back barrier sediments may yield basin fill configurations but generally include abundant signal attenuating units the gpr data calibrated with information from cores were collected across swash aligned and drift aligned barriers in a variety of wave and tidal energy settings application of a 120 mhz antenna as used in this study enables portrayal of a range of sedimentary units from individual bedforms on single records to entire barrier elements using large numbers of intersecting gpr sections at maximum vertical resolutions that vary between 0 2 m and 0 7 m the most important drawback of gpr in the coastal environment is attenuation of the electromagnetic em signal by layers of salt marsh peat or by brackish or salty groundwater primarily along barrier edges this disadvantage is offset by many benefits data can be collected at rates of several km per day making gpr an excellent reconnaissance tool a core that is used in the calibration of gpr data can be matched with great accuracy to its position on the complementary gpr record allowing detailed correlation between lithostratigraphy and reflection configuration