the effects of large organic debris on sediment processes and stream morphology in vermont abstract research conducted on a small third order stream in the green mountains of vermont suggests that large organic debris lod has an important influence on areal sorting and storage of sediment spacing of pool riffle sequences and channel geometry large organic debris forms local base levels that trap over 26 cubic meters of sediment and cause over 14 percent of the vertical drop along a 412 meter study reach on tiger brook vermont the local base levels created by large organic debris accumulations are the most important control on sediment storage between large bedrock knickpoints along the study reach focusing fine grained sediment deposition in areas stable at low and moderate discharges the micro steps created by these lod local base levels dominate gradient and sediment storage at short time scales between the slowly evolving large bedrock macrosteps the relation that exists among the volumes of standing timber adjacent to the channel lod and sediment stored behind lod seems to indicate that large organic debris causes a negative feedback type mechanism where channel degradation leads to increased standing timber recruitment and large organic debris sediment storage sites

stabilization of a gravel channel by large streamside obstructions and bedrock bends jacoby creek northwestern california jacoby creek bed width 12 m bankfull discharge 32 6 m 3 s contains stationary gravel bars that have forms and positions controlled by numerous large streamside obstructions bedrock outcrops large woody debris and rooted bank projections and bedrock bends bank projection width and bar volume measured in 104 channel segments 1 bed width long are significantly cross correlated at lags of 1 3 and 4 indicating the tendency for large obstructions and bends to form bars 3 to 4 bed widths downstream and 1 bed width upstream all of the 18 bars downstream of large obstructions or bends in the study reach were along the obstruction side of the channel or outside bank of the bend most of the pools 85 were next to large obstructions or in bends conversely 92 of large obstructions or bends had pools comparison of the volume of four bars with volumetric bar changes and volume of bedload transported during four high flow events suggests that rates of sediment transport were sufficient to cause major changes in bars during bankfull events the only important channel changes observed in 4 yr however have been associated with the movement of large woody debris and with changes in the angle at which the flow approaches an obstruction a general model is proposed that large obstructions and nonalluvial bends stabilize the form and location of gravel bars bars are stabilized by two related mechanisms 1 large obstructions and bends cause intense quasi steady secondary circulation in scour holes that terminate upstream bars at fixed locations obstruction width channel deflection scour hole width and bed width were measured at 26 obstructions these data show that obstructions wider than approximately one third of the bed form pools spanning the entire channel and thus terminating bars smaller obstructions form scour holes contained within a single bar 2 bars are deposited upstream of large obstructions and sharp bends because of backwater reductions in stream power bars are deposited downstream because flow energy is expended around obstructions and bends and because the flow expands downstream of constrictions that result from large obstructions the formation of bars and pools inherent in many gravel channels can thus be enhanced and fixed in position by flow structures set up around large obstructions and bends formed of resistant materials

the 1983 hydraulic jump in crystal rapid implications for river running and geomorphic evolution in the grand canyon for the last 1 000 to 10 000 years dozens of large debris fans have severely constricted the path of the colorado river in the grand canyon arizona at most of these fans the narrowest part of the channel eroded by the river is 0 5 of the upstream width at crystal creek a debris fan was emplaced in 1966 constricting the channel of the colorado river to about 0 25 of its upstream width between 1967 and 1983 forming a major rapid in this paper the hydraulics of crystal creek rapid are described and an analysis is presented to support the hypothesis that the major wave in the rapid was a normal wave one type of hydraulic jump hydraulic jumps rarely occur in natural river channels with erodible beds but one was present at crystal rapid because of the unusually severe constriction of the colorado river by the 1966 debris fan observations on the hydraulics of the river during this time including mid 1983 when progressively higher discharges culminated in excess of 96 000 cubic feet per second h

debris fan constrictions and flood hydraulics in river canyons some implications from two dimensional flow modelling rapids in river canyons are frequently found at sites where debris fans constrict flow along the channel whereas some fans may have persisted in the same location with unchanging geometry for centuries to millennia others have changed in response to flow conditions imposed by successive floods such a change in boundary conditions may alter local flow hydraulics this paper utilizes two dimensional flow modelling to compare flood hydraulics along two alternative versions of an idealized reach of a river canyon one with uniform width gradient and cross section and a second perturbed by a prominent debris fan along the valley wall the flow pattern along the reach with the fan is far more complex than the pattern along the uniform reach maximum velocity along the debris fan reach is up to 50 per cent higher than along the uniform reach maximum bed shear stress is up to three or four times higher and an area of supercritical flow is predicted extending from the nose of the fan into the zone of flow expansion immediately downstream comparison of model output along longitudinal profiles of the two reaches indicates that the backwater effect of the fan extends several valley widths upstream predicted flows based on the same stage are as much as 190 to 230 per cent greater along the uniform reach than along the debris fan reach reconstruction of palaeoflood discharge based on remnant flood marks in the vicinity of the fan would be sensitive to assumptions about boundary conditions that existed in the past this effect relaxes over a longitudinal distance of several hundred metres furthermore there are significant cross stream gradients that change slope and direction several times in the vicinity of the fan calling into question the utility of one dimensional step backwater hydraulic models for predicting high water marks in areas of complex valley morphology

the effects of rock uplift and rock resistance on river morphology in a subduction zone forearc oregon usa relationships between riverbed morphology concavity rock type and rock uplift rate are examined to independently unravel the contribution of along strike variations in lithology and rates of vertical deformation to the topographic relief of the oregon coastal mountains lithologic control on river profile form is reflected by convexities and knickpoints in a number of longitudinal profiles and by general trends of concavity as a function of lithology volcanic and sedimentary rocks are the principal rock types underlying the northern oregon coast ranges between 46 30 and 45 n where mixed bedrock alluvial channels dominate average concavity is 0 57 in this region in the alluviated central oregon coast ranges between 45 and 44 n values of concavity are on average the highest 0 82 south of 44 n however bedrock channels are common and 0 73 mixed bedrock alluvial channels characterize rivers in the klamath mountains from 43 n south 0 64 rock uplift rates of 0 5 mm a 1 mixed bedrock alluvial channels and concavities of 0 53 0 70 occur within the northernmost coast ranges and klamath mountains for rivers flowing over volcanic rocks 0 53 and 0 72 for reaches crossing sedimentary rocks whereas channel type and concavity generally co vary with lithology along much of the range rivers between 44 5 and 43 n do not follow these trends concavities are generally greater than 0 70 alluvial channels are common and river profiles lack knickpoints between 44 5 and 44 n despite the fact that lithology is arguably invariant moreover rock uplift rates in this region vary from low 0 5 mm a 1 to subsidence 0 mm a 1 these observations are consistent with models of transient river response to a decrease in uplift rate conversely the rivers between 44 and 43 n have similar concavities and flow on the same mapped bedrock unit as the central region but have bedrock channels and irregular longitudinal profiles suggesting the river profiles reflect a transient response to an increase in uplift rate if changes in rock uplift rate explain the differences in river profile form and morphology it is unlikely that rock uplift and erosion are in steady state in the oregon coastal mountains copyright 2006 john wiley sons ltd

studies of colloids and suspended particles cigar lake uranium deposit saskatchewan canada abstract the cigar lake u deposit is located in northern saskatchewan in the eastern part of the athabasca sandstone basin and consists of a high grade ore body up to 55 u located at a depth of 430 m as part of a study to evaluate the analog features of this deposit with respect to a disposal vault for waste nuclear fuel colloids 1 450 nm and suspended particles 450nm in groundwater have been investigated to evaluate their effect on element transport through the u deposit tangential flow ultrafiltration was used to concentrate particles from 501 groundwater samples in order to characterize the size distribution concentration composition and natural radionuclide content of particles in representative parts of the u deposit although cigar lake groundwaters contain particles in all sizes ranging from 10 nm to slightly larger than 20 m most samples contained a relatively high concentration of colloids in the 100 400 nm size range particle compositions are similar to the composition of minerals in the sandstones and ore body suggesting that particles in groundwater are generated by the erosion of fracture lining minerals as a result particle concentrations in groundwater are affected by the integrity of the host rock in some piezometers the high initial concentrations of suspended particles which may have been drilling artifacts decreased during the collection of the first 350 1 although colloid concentrations fluctuated during sampling there are no indications that these concentrations will be permanently reduced by continued groundwater pumping the observed colloid and suspended particle concentrations in the deep groundwaters are too low to have a significant impact on radionuclide migration provided that radionuclide sorption is reversible if radionuclides are irreversibly sorbed to particles they cannot sorb to the host rock and their migration can only be evaluated with an understanding of particle mobility the data for dissolved and particulate u th and ra were used to calculate field derived distribution ratios rd between particles and groundwater the wide range of observed rd values indicates that these radionuclides in particulate form are not in equilibrium with groundwater u series isotope data indicated that most of the u and ra on particles was derived from groundwater some particles could have retained their u for as long as 8000 a the u and ra contents of particles in the ore and surrounding clay zones are significantly higher than in particles from sandstone suggesting that the clay has been an effective barrier to particle migration

monument creek debris flow 1984 implications for formation of rapids on the colorado river in grand canyon national park a recent debris flow in monument creek illustrates the nature of debris flows in small tributaries and their hydrologic effects on the colorado river in grand canyon national park a debris avalanche originated in the permian esplanade sandstone of the supai group during intense rainfall on july 27 1984 and fell 600 m into monument creek forming a 7 m high barrier across the channel the subsequent debris flow traveled 4 5 km to the colorado river and achieved velocities of 3 4 to 4 0 m s and a peak discharge of 100 to 120 m 3 s the flow consisted of a main pulse followed by subsequent pulses of debris flow or hyperconcentrated flow the main pulse moved boulders as large as 2 7 m in diameter and deposition at the mouth of monument creek enlarged the fan surface and significantly constricted the colorado river most of the major rapids on the colorado river in grand canyon national park appear to be maintained by episodic debris flows

bedform morphology of salmon spawning areas in a large gravel bed river while the importance of river channel morphology to salmon spawning habitat is increasingly recognized quantitative measures of the relationships between channel morphology and habitat use are lacking such quantitative measures are necessary as management and regulatory agencies within the pacific northwest region of the usa and elsewhere seek to quantify potential spawning habitat and develop recovery goals for declining salmon populations the objective of this study was to determine if fall chinook salmon oncorhynchus tshawytscha spawning areas in the snake river idaho usa were correlated with specific bedform types at the pool riffle scale a bedform differencing technique was used to objectively quantify the longitudinal riverbed profile into four distinct pool riffle units that were independent of discharge the vertical location of thalweg points within these units was quantified with a riffle proximity index chinook salmon spawning areas were mapped and correlated with the pool riffle units through the use of cross tabulation tables the results indicate that 84 of fall chinook salmon spawning areas were correlated with riffles 2 57 5 df 3 p 0 001 with 53 of those areas located on the upstream side of riffle crests the majority of snake river fall chinook salmon spawning occurred at elevations greater than 80 of the difference in elevation between the nearest riffle crest and pool bottom the analyses of bedform morphology will assist regional fish managers in quantifying existing and potential fall chinook salmon spawning habitat and will provide a quantitative framework for evaluating general ecological implications of channel morphology in large gravel bed rivers

a review on natural and human induced geohazards and impacts in karst karst environments are characterized by distinctive landforms related to dissolution and a dominant subsurface drainage the direct connection between the surface and the underlying high permeability aquifers makes karst aquifers extremely vulnerable to pollution a high percentage of the world population depends on these water resources moreover karst terrains frequently underlain by cavernous carbonate and or evaporite rocks may be affected by severe ground instability problems impacts and hazards associated with karst are rapidly increasing as development expands upon these areas without proper planning taking into account the peculiarities of these environments this has led to an escalation of karst related environmental and engineering problems such as sinkholes floods involving highly transmissive aquifers and landslides developed on rocks weakened by karstification the environmental fragility of karst settings together with their endemic hazardous processes have received an increasing attention from the scientific community in the last decades concurrently the interest of planners and decision makers on a safe and sustainable management of karst lands is also growing this work reviews the main natural and human induced hazards characteristic of karst environments with specific focus on sinkholes floods and slope movements and summarizes the main outcomes reached by karst scientists regarding the assessment of environmental impacts and their mitigation

valley width variation influences riffle pool location and persistence on a rapidly incising gravel bed river abstract decades of research have demonstrated that gravel bed rivers exhibit multiple spatial scales of landform nonuniformity landform features such as valley wall oscillations alluvial fans terraces river meanders point bars boulder clusters and logjams contribute to river corridor heterogeneity further studies have shown that the locations of riffles and pools in gravel bed rivers are closely associated with the spatial pattern of river corridor morphological variability these studies imply but do not directly test that persistence of riffles and pools through time is also conditioned by landform variability mechanistically it may be hypothesized that overbank flows interact hydraulically with oscillating valley walls by way of a mechanism known as flow convergence routing in such circumstances can variation in valley width influence channel morphology forcing riffle pool location and persistence to address this question research was performed on a valley confined wandering gravel bed reach of the regulated lower yuba river california usa that is incising from reduced sediment supply and flow regulation after a historic period of mining related valley sedimentation this study quantified stream planform change 1984 2006 and elevation change 1999 2006 using eight aerial photo sets and two digital elevation models and it qualitatively assessed channel change in older aerial photos going back to 1937 analysis revealed that the river has undergone rapid incision 0 11 m year and planform change in response to frequent floods yet eight riffles persisted in the same locations which coincided with the locally wide areas of the valley longitudinal profiles revealed that deep pools were associated with long valley constrictions geomorphic analysis and design need to explicitly account for multiple scales of landform nonuniformity in order to rehabilitate natural fluvial processes

conditioning factors in flooding of karstic poljes the case of the zafarraya polje south spain abstract the zafarraya polje undergoes periodical flooding of which the last episode 1996 1997 was analysed in detail on this paper on the basis of the retention curves of the two lakes that formed in the northwestern and southwestern sectors we calculated the total infiltration capacity of the polje to have a maximum value of 3 3 5 m3 s and so we infer that when the flow of the arroyo de la madre exceeds this figure there will be a risk of flooding in the polje we also propose a model for the 1996 flood that can be extended to other similar occurrences in this and other poljes where we can establish the role played by groundwater and surface water during this flood in response to the heavy precipitation the flow of the arroyo de la madre rose abruptly exceeding the infiltration capacity of the main swallow holes on the polje causing first the northern lake and then the southern lake to form with only surface water supply the water table of the karst aquifer rose sharply reaching a situation of equilibrium between the level in the lakes and the water table in this sector of the karst aquifer that prevented infiltration through the swallow holes in the case of the southern lake there were even cases of swallow holes that began to operate as estavelles during this phase of maximum flooding one single lake was present which was divided into two once more when the water table of the karst aquifer in the polje sector began to fall and surface supply also began to decrease

single event time series analysis in a binary karst catchment evaluated using a groundwater model lurbach system austria the lurbach karst system styria austria is drained by two major springs and replenished by both autogenic recharge from the karst massif itself and a sinking stream that originates in low permeable schists allogenic recharge detailed data from two events recorded during a tracer experiment in 2008 demonstrate that an overflow from one of the sub catchments to the other is activated if the discharge of the main spring exceeds a certain threshold time series analysis autocorrelation and cross correlation was applied to examine to what extent the various available methods support the identification of the transient inter catchment flow observed in this binary karst system as inter catchment flow is found to be intermittent the evaluation was focused on single events in order to support the interpretation of the results from the time series analysis a simplified groundwater flow model was built using modflow the groundwater model is based on the current conceptual understanding of the karst system and represents a synthetic karst aquifer for which the same methods were applied using the wetting capability package of modflow the model simulated an overflow similar to what has been observed during the tracer experiment various intensities of allogenic recharge were employed to generate synthetic discharge data for the time series analysis in addition geometric and hydraulic properties of the karst system were varied in several model scenarios this approach helps to identify effects of allogenic recharge and aquifer properties in the results from the time series analysis comparing the results from the time series analysis of the observed data with those of the synthetic data a good agreement was found for instance the cross correlograms show similar patterns with respect to time lags and maximum cross correlation coefficients if appropriate hydraulic parameters are assigned to the groundwater model the comparable behaviors of the real and the synthetic system allow to deduce that similar aquifer properties are relevant in both systems in particular the heterogeneity of aquifer parameters appears to be a controlling factor moreover the location of the overflow connecting the sub catchments of the two springs is found to be of primary importance regarding the occurrence of inter catchment flow this further supports our current understanding of an overflow zone located in the upper part of the lurbach karst aquifer thus time series analysis of single events can potentially be used to characterize transient inter catchment flow behavior of karst systems

use of a flood routing model to assess lateral flows in a karstic stream implications to the hydrogeological functioning of the grands causses area tarn river southern france the aim of this study is to assess the spatio temporal variability of lateral flows in the streams of a large karstic basin to construct a conceptual model of karst contributions to flood generation the lateral flows of the tarn river which crosses the grands causses karst zone in southern france were investigated between several gauging stations along the river first through analysing the lateral flows on an event time scale of 30 floods it was possible to identify the losing and gaining reaches highlighting a highly variable attenuation amplification role of karsts on flood generation second the diffusive wave model was used to quantify the lateral flows on an hourly time step within a flood event the simulations show a high variability of lateral outflows and inflows within a same reach according to the hydrometeorological conditions with in some cases an inversion of the lateral flow direction during the flood the results highlight complex surface groundwater exchanges during a single flood event with high river losses despite the concurrent flow of large springs feeding the stream this spatio temporal variability of the karst influence on flood generation was linked to the aquifer s structure which has improved the understanding of the hydro geo logical functioning of the grands causses massif finally the new methodology proposed here opens challenging perspectives towards a framework for the analysis of surface groundwater exchanges in karstic rivers

equilibrium pool dimensions and sediment sorting patterns in coarse grained new england channels abstract pools and riffles are natural bedforms that produce variations in width and depth along channels deemed critical for aquatic habitat an understanding of this morphology is necessary for the successful design of a reconstructed or restored channel to better understand pool geometry and sorting characteristics of new england channels characterizations of pool geometry were performed on 145 different pools strongly influenced by channel constrictions characterizations of channel bed sediments were also performed at 34 of these locations data from 120 pools were used in least squares multiple regression analysis with 19 different independent variables to develop prediction equations for pool depth length and exit slope gradient these equations were then tested using the 25 remaining pools eighteen different geometric variables were then used to predict sediment 50 values in pool centers pool exit slopes and riffles for the subset of 34 samples the regression analyses for pool geometry indicate that pool depth is significantly influenced to a decreasing degree by pool exit slope width constriction gradient constriction width drainage area upstream channel width and the exit slope expansion ratio with an r 2 value of 0 53 similarly pool length is influenced by channel gradient location of the channel constriction pool width drainage area and constriction length with an r 2 value of 0 72 the gradient of pool exit slope is influenced by drainage area channel gradient and constriction gradient with an r 2 value of 0 34 however r 2 values for exit slope increased to 0 65 when sediment d 50 data were utilized using the resulting regression equations to predict dimensions for the 25 verification pools yields average residuals near zero although moderate variations do exist a tukey kramer hsd comparison of the means for sediment 50 values indicates pool sediments are significantly coarser than pool exit slope and riffle sediments for the subset of 34 pools regression analyses also suggest significant relations between the size of sediments in pools and riffles and a combination of geometric variables with r 2 values that range from 0 45 to 0 62 the results suggest that pool dimensions are related to basin wide variability and local hydraulic conditions the findings also suggest that the characteristics of constrictions and the downstream section of pools provide an important control on scouring and sorting characteristics throughout the pool riffle morphology

formation and maintenance of a forced pool riffle couplet following loading of large wood abstract pool riffle maintenance has been documented in numerous studies but it has been almost impossible to characterize detailed natural pool riffle formation mechanisms because of the lack of baseline data prior to pool establishment in 2013 a study was conducted on the blackledge river in connecticut to document the formation of a new pool riffle couplet on a section of river that had previously been studied from 1999 to 2001 in 2001 the study reach contained a scour hole with a residual depth of 0 08 0 09 m downstream of a 1930s paired deflector with no identifiable riffle immediately downstream at this time a large severely undercut hemlock tree was noted along the left bank sometime between fall 2001 and 2004 the tree fell perpendicular to flow across the channel and formed a large wood lw jam and new pool riffle couplet several meters downstream of the old scour hole pool spacing along the reach decreased from 4 47 bankfull widths bfw in 1999 to 3 83 bfw after the new pool riffle couplet formed the new pool has a residual depth the water depth of the streambed depression below the elevation of the immediate downstream hydraulic control of 1 36 0 075 to 1 59 0 075 m which resulted from a combination of 1 32 0 09 m or less of incision below the old scour hole 95 6 or less of the depth increase and up to 0 18 0 09 m of downstream deposition and associated backwater formation 13 2 or less of the depth increase to assess dynamic stability of the pool riffle couplet over several flood cycles surficial fine sediment and organic material along the reach were quantified the 23 m long pool stores 25 7 of the surficial fine grained sediments and 15 4 of organic material along a 214 m long reach that includes one additional artificially created pool an adjacent 50 m long secondary channel impacted by the lw jam stores 65 3 of the surficial fine grained sediments and 54 8 of organic material along the full reach

pool and riffle characteristics in relation to channel gradient abstract the depths of pools relative to the dephts of runs and riffles were correlated with reach scale channel gradient along three rivers in coastal northern california the sample included 122 pools formed in channels with gradients from 0 172 to 0 002 relative pool depth on these rivers and relative distance between pools increase as channel gradient decreases mean pool riffle depth is 2 8 1 at the highest channel gradient and 6 2 1 at the lowest gradient while mean pool riffle length is 1 0 8 at high channel gradient and 1 1 8 at low channel gradient we hypothesize that these trends reflect changes in energy expenditure with decreasing gradient as a result of the flow s ability to erode its channel boundaries channel reaches with high gradients are characterized by resistant channel boundaries coarse material and relatively low discharge and total stream power channel reaches with low gradients have less resistant channel boundaries finger grained bed material and higher values of discharge and total stream power these changes in channel and flow characteristics with decreasing gradient result in flows in high gradient reaches expending a greater proportion of their energy in overcoming boundary and internal resistance with less energy available for channel bed scour and the formation of pools in their relatively resistant channels in contrast with less energy available for channel bed scour the channel bed creating deeper pools because the channel boundaries are less resistant and the proportion of flow energy available for sediment entrainment and transport should be greater

sediment deposition and transport patterns following a reservoir sediment release a reservoir sediment release on the north fork poudre river supplied 7000 m3 of silt to pebble sized sediment to an originally boulder bed channel deposition along the 12 km of channel downstream from the reservoir occurred primarily in pools during the subsequent snowmelt hydrograph sediment was progressively scoured from the upstream and then the downstream pools initial sediment reworking in the pools created a deep narrow thalweg scoured to the original pool bed with additional sediment deposition in lateral eddies continued reworking reduced but did not completely remove these eddy deposits the channel became supply limited with respect to finer grain sized fractions clay to medium sand first at upstream and then at downstream sites and eventually became supply limited with respect to coarser grain sized fractions coarse sand to pebbles bedload transport rates at a site were strongly linked to the depletion of sediment stored in upstream pools magnitude duration and sequence of flows were all important controls on bedload transport and return of the channel to its prerelease state

the characteristics of turbulence in a shear zone downstream of a channel constriction in a coarse grained forced pool a field based project was initiated to characterize the influence of varying discharge and bed topography along a pool exit slope on the strength of turbulence generated by vortex shedding velocities were measured with an adv downstream of a boulder constriction within a shear zone of a large pool measurements were repeated for four flows that varied from 20 to 50 of bankfull discharge an additional longitudinal profile was conducted along the pool thalweg plots of velocity demonstrate high near bed velocities and turbulence levels in the pools turbulence levels were highest closer to the constriction in the shear zone turbulent kinetic energy decayed in the downstream direction in response to the bed topography and at lower discharges instantaneous velocities are large enough to temporarily lift pebbles at this depth it appears that instantaneous forces created by vortex shedding may play an important role in scouring pools downstream of constrictions the turbulence may also respond to changes in bed topography in a manner that encourages feedbacks among bed topography characteristics of turbulence and sediment transport

pool spacing in forest channels field surveys of stream channels in forested mountain drainage basins in southeast alaska and washington reveal that pool spacing depends on large woody debris lwd loading and channel type slope and width mean pool spacing in pool riffle plane bed and forced pool riffle channels systematically decreases from greater than 13 channel widths per pool to less than 1 channel width with increasing lwd loading whereas pool spacing in generally steeper step pool channels is independent of lwd loading although plane bed and pool riffle channels occur at similar low lwd loading they exhibit typical pool spacings of greater than 9 and 2 4 channel widths respectively forced pool riffle channels have high lwd loading typical pool spacing of 2 channel widths and slopes that overlap the ranges of free formed pool riffle and plane bed channel types while a forced pool riffle morphology may mask either of these low lwd loading morphologies channel slope provides an indicator of probable morphologic response to wood loss in forced pool riffle reaches at all study sites less than 40 of the lwd pieces force the formation of a pool we also find that channel width strongly influences pool spacing in forest streams with similar debris loading and that reaches flowing through previously clear cut forests have lower lwd loading and hence fewer pools than reaches in pristine forests

contribution of spectral coherency analysis and tracer test to study leakage at the doosti dam reservoir iran and turkmenistan the doosti dam was built across the harirood river on the border between turkmenistan and iran during the reservoir impounding leakage occurred as new springs through the sandstone layers of the pesteleigh aquifer and limy sandstone and limestone layers of the neyzar kalat aquifer at the right abutment of the dam to evaluate the grout curtain operation a tracer test was carried out by injection of uranine in a borehole located at the upstream of grout curtain in the pesteleigh aquifer tracer test results demonstrated a diffuse flow component through the grout curtain in the pesteleigh aquifer but no tracer was detected at the main leakage point sp1 spring emerged downstream of grout curtain from the neyzar kalat aquifer using the spectral coherency function the lag time between changes in the water level of the injection borehole and water level in the tracer detected boreholes or discharge of the tracer detected springs was determined linear regression analyses indicated that the estimated lag time by the time series analysis was close to the first arrival time of the tracer therefore the estimated velocities based on the lag time of time series could be considered close to the calculated velocities based on the first arrival time of the tracer the estimated groundwater velocities based on the time series analysis ranged from 3 91 to 20 31 m h 1 showed that diffuse flow dominated pathways from the reservoir toward the downstream boreholes in the neyzar kalat aquifer while conduit flow was present within the pathways toward the sp1 spring regarding the reservoir volume the negligible amount of leakage at the maximum water level of the reservoir confirmed well overall operation of the grout curtain at the dam site

geostatistical analysis of the effects of stage and roughness on reach scale spatial patterns of velocity and turbulence intensity although previous research has documented well organized interactions between the turbulent flow field and an irregular boundary the spatial variability of turbulent flow characteristics at the reach scale remains poorly understood in this paper we present detailed field measurements of three dimensional flow velocities and turbulence intensities in a high gradient cobble bed riffle from three discharges additional data on sediment grain size and bed topography were used to characterize boundary roughness an acoustic doppler velocimeter was used to measure velocities along five cross sections within a 6 in long reach of the north fork cache la poudre river vertical profiles were also measured along the channel thalweg we adopted a spatially explicit stochastic hydraulic approach and focused not on coherent flow structures per se but rather time averaged reach scale variability and spatial pattern scaling velocities and turbulence intensities by the reach averaged friction velocity u accounted for changes in flow depth and enabled comparisons among the three discharges we quantified the effects of stage and roughness by assessing differences among probability distributions of hydraulic quantities and by examining geostatistical metrics of spatial variability we computed semivariograms for streamwise and transverse directions and fit parametric models to summarize the spatial structure of each variable at each discharge cross correlograms were also used to describe the local and lagged effects of boundary roughness on flow characteristics although the probability distributions yielded some insight incorporating spatial information revealed important elements of stage dependent flow structure the development of secondary currents and flow convergence at higher stages were clearly documented in maps and semivariograms in general the spatial structure of the flow field became smoother and more continuous as stage increased and the effects of boundary roughness diminished although roughness elements do influence velocities and turbulence intensities our data suggest that the flow primarily responds to the gross morphology of the channel and that flow depth is the primary control on flow structure the geostatistical framework proved useful and our results indicate that a complete stochastic description must also be explicitly spatial c 2006 elsevier b v all rights reserved

structure and water storage capacity of a small karst aquifer based on stream discharge in southwest china summary karst spring stream discharge reflects the global configuration of the aquifer however quantitative description of the aquifer structure such as effective porosity neff and water storage capacity by the discharge analysis is difficult because of the complex conduit fracture system this study attempted to quantify the characteristics of karst aquifer based on discharge recession and time series analysis methods three recession models including modified maillet mangin and boussinesq models were evaluated to choose the most suitable one for analyzing the aquifer structure and auto correlation and cross correlation functions were applied to study the aquifer response in both year and rainfall event time scales the results showed that the modified maillet model was more suitable in the study catchment with mangin model overestimating and boussinesq model underestimating the discharge the neff was 3 73 for the total aquifer and it was 0 07 0 33 and 3 33 for the conduit fracture and matrix respectively based on a case study of a rainfall event with precipitation of 68 mm the water volumes drained by the three media were 25 43 33 40 and 41 17 respectively this indicates that although conduit network is not very developed with lower neff it is still an important water transmissive element draining more than a quarter of water after the rainfall event the memory time of the aquifer was 4 days for the year scale and 8 h for the rainfall event 68 mm scale this demonstrates that the aquifer has a well developed drainage system with a quick response to the rainfall the above results provide further insights for hydrological processes modeling and water resources management for the small catchment in karst regions

flume simulation of recirculating flow and sedimentation experiments were conducted in a 4 m wide flume to simulate recirculating flow and sedimentation in a lateral eddy within a channel expansion the percentage of main stem sediment that was captured by the eddy decreased from 37 when the eddy was empty to 24 when sand filled approximately 32 of the eddy volume the reattachment bar within the eddy grew in an upstream direction and the finest size sediment was deposited in the lee of the obstruction both observations are consistent with field observations measurements of reattachment length during sediment transport 0 5 1 0 kg s at constant discharge 0 60 m3 s show that reattachment length depends not only on characteristics of the expanding jet but also on the topography of the channel bed downstream reattachment length decreased when part of the channel expansion was filled by an aggrading midchannel bar comparison of these results with measurements in the colorado river in grand canyon suggests that downstream channel irregularities play a large role in controlling the length of eddies in natural rivers

rainfall runoff relations for karstic springs part i convolution and spectral analyses karstic basins contain large reserves of subsurface water in this paper three karstic systems located in the pyrenees mountains ariege france are studied long records of rainfall and discharge rates for these karstic springs are available sampled at different rates daily hourly and half hourly this study aims at illustrating and assessing the capabilities and limitations of linear black box methods for analysing rainfall runoff type relationships and reconstructing runoffs from rainfall rate data using such systems in this study precipitation and discharge rates are considered as two autocorrelated and cross correlated stochastic processes a linear and stationary rainfall runoff model is adopted which is used for identification and simulation purposes different versions are analysed including a model based on a convolution integral between the precipitation rate p and a transfer function h t which can be thought of as the unit impulse response of the system it is shown that this linear stochastic model i e the statistical version although accurate in some respects does not represent the hydraulic behaviour of the system very well during low flow episodes and floods it is also shown that the use of fourier analysis alone does not lead to a satisfactory reconstitution of observed runoff sequences for these reasons the use of non linear random process input output models based on volterra integral series is proposed and discussed

natural colloids and suspended particles in the whiteshell research area manitoba canada and their potential effect on radiocolloid formation abstract natural colloids 1 450 nm and suspended particles 450 nm were characterized in groundwaters of the whiteshell research area of southern manitoba to evaluate their potential role in radionuclide transport through fractured granite data on particle concentrations size distributions compositions and natural radionuclide content were collected to predict radionuclide formation and to provide a database for future colloid migration studies the concentrations of colloids between 10 and 450 nm ranged between 0 04 and 1 mg l the concentrations of suspended particles which require higher groundwater velocities for transport varied from 0 04 to 14 mg l colloid 10 450 nm concentrations as low as these observed in whiteshell research area groundwater would have a minimal effect on radionuclide transport assuming that radionuclide sorption on colloids is reversible if radiocolloid formation is not reversible and radionuclide containing colloids cannot sorb onto fracture walls the importance of natural colloids in radionuclide transport will depend upon particle migration properties

aquifer response to stream stage and recharge variations i analytical step response functions abstract laplace transform step response functions are presented for various homogeneous confined and leaky aquifer types and for anisotropic homogeneous unconfined aquifers interacting with perennial streams flow is one dimensional perpendicular to the stream in the confined and leaky aquifers and two dimensional in a plane perpendicular to the stream in the water table aquifers the stream is assumed to penetrate the full thickness of the aquifer the aquifers may be semi infinite or finite in width and may or may not be bounded at the stream by a semipervious streambank the solutions are presented in a unified manner so that mathematical relations among the various aquifer configurations are clearly demonstrated the laplace transform solutions are inverted numerically to obtain the real time step response functions for use in the convolution or superposition integral to maintain linearity in the case of unconfined aquifers fluctuations in the elevation of the water table are assumed to be small relative to the saturated thickness and vertical flow into or out of the zone above the water table is assumed to occur instantaneously effects of hysteresis in the moisture distribution above the water table are therefore neglected graphical comparisons of the new solutions are made with known closed form solutions

stream aquifer interaction model with diffusive wave routing a practical approach to modeling the hydraulic interaction of a stream and aquifer via streambed leakage is based on the established u s geological survey usgs model modflow to represent flood wave propagation and the associated bank storage modflow s stream module is replaced by the muskingum cunge diffusive wave routing scheme the diffusive wave model closely approximates a dynamic model of a flood wave s speed shape and streambed leakage because the stream responds more rapidly to disturbances than the aquifer streambed leakage is calculated at the flood routing time scale in order to properly represent the stream aquifer coupling however both the relative magnitude and timing of aquifer response to a flood wave depend on the strength of this coupling we find discrepancies in both the flood wave and the streambed leakage when the wave and ground water motions are evaluated at different time scales these discrepancies are significant in the case of a strong stream aquifer coupling for which equal aquifer and flood routing time steps may be required wave diffusion and bank storage are shown to be comparable in magnitude and should therefore be included in stream aquifer interaction models diffusive wave routing more accurately represents wave propagation bed leakage and aquifer response if short aquifer time steps are taken and is preferable to the stream module for simulating short time transients however the stream module is useful for simulating large time frames if accurate modeling of the flood wave propagation is not required

water exchange and pressure transfer between conduits and matrix and their influence on hydrodynamics of two karst aquifers with sinking streams summary karst aquifers are heterogeneous media where conduits usually drain water from lower permeability volumes matrix and fractures for more than a century various approaches have used flood recession curves which integrate all hydrodynamic processes in a karst aquifer to infer physical properties of the movement and storage of groundwater these investigations typically only consider flow to the conduits and thus have lacked quantitative observations of how pressure transfer and water exchange between matrix and conduit during flooding could influence recession curves we present analyses of simultaneous discharge and water level time series of two distinctly different karst systems one with low porosity and permeability matrix rocks in southern france and one with high porosity and permeability matrix rocks in north central florida usa we apply simple mathematical models of flood recession using time series representations of recharge storage and discharge processes in the karst aquifer we show that karst spring hydrographs can be interpreted according to pressure transfer between two distinct components of the aquifer conduit and matrix porosity which induce two distinct responses at the spring water exchange between conduits and matrix porosity successively control the flow regime at the spring this exchange is governed by hydraulic head differences between conduits and matrix head gradients within conduits and the contrast of permeability between conduits and matrix these observations have consequences for physical interpretations of recession curves and modeling of karst spring flows particularly for the relative magnitudes of base flow and quick flow from karst springs finally these results suggest that similar analyses of recession curves can be applied to karst aquifers with distinct physical characteristics utilizing well and spring hydrograph data but information must be known about the hydrodynamics and physical properties of the aquifer before the results can be correctly interpreted

particle size and mineralogical composition of inorganic colloids in waters draining the adit of an abandoned mine goesdorf luxembourg particle size distributions and the mineralogy of inorganic colloids in waters draining the adit of an abandoned mine goesdorf luxembourg were quantified by single particle counting based on light scattering 100 nm 2 m combined with transmission electronic microscopy coupled with energy dispersive spectroscopy and selected area electron diffraction this water system was chosen as a surrogate for groundwaters the dependence of the colloid number concentration on colloid diameters can be described by a power law distribution in all cases power law slopes ranged from 3 30 to 4 44 depending on water ionic strength and flow conditions the same main mineral types were found in the different samples 2 1 phyllosilicates illite and mica chlorite feldspars albite and orthoclase calcite and quartz with a variable number of fe oxide particles the colloid mineralogical composition closely resembles the composition of the parent rock spatial variations in the structure and composition of the rock in contact with the waters i e fissured rock versus shear joints are reflected in the colloid composition the properties of the study colloids as well as the processes influencing them can be considered as representative of the colloids present in groundwaters

hydrologic and topographic variability modulate channel change in mountain rivers summary the relationships between flow hydrology topography and channel change in mountain rivers is important to understanding landscape evolution the structure and persistence of aquatic habitat and also the physiochemical cycling of upstream derived organic and inorganic materials there is a paucity of detailed studies that analyze the joint roles of hydrology and topography in controlling multiple mechanisms of channel change in mountain rivers in this study gravel and cobble channel change in a bedrock river canyon were analyzed in light of a controlled yet natural experiment where 4491 metric tonnes of rounded gravel and cobble was augmented below a sediment barrier dam in a 1200 m long mountain river reach that had no prior sources of rounded gravel or cobble and still experiences floods above the bankfull discharge the overall study goal was to investigate how flow hydrology can modulate multiple channel change processes depending on the topographic features engaged by the flow channel change was assessed via differencing of high resolution repeat topographic and bathymetric surveys along with cm scale aerial photography post injection statistical tests used to implicate topographic feature specific mechanisms of channel change that vary with discharge included analyzing geomorphic covariance structures of flow dependent width bed elevation and channel change as well as autocorrelation of flow width spatial series stage dependent topographic steering was inferred from associations of erosion and deposition with changes in 2d model derived flow directions at multiple discharges a variety of mechanisms of channel change were qualitatively and quantitatively confirmed including particle hiding topographic steering eddying and flow convergence no single mechanism explained the observed patterns of channel change but rather it is thought that process blending occurs as modulated by the interactions of flow hydrology with complex topography results from this study suggest that both existing channel boundary variability and input hydrologic variability work together to create hydrodynamic spatial patterns that control the fate and transport of sediments in mountain rivers and ultimately their spatial structure

holocene debris flows on the colorado plateau the influence of clay mineralogy and chemistry holocene debris flows do not occur uniformly on the colorado plateau province of north america debris flows occur in specific areas of the plateau resulting in general from the combination of steep topography intense convective precipitation abundant poorly sorted material not stabilized by vegetation and the exposure of certain fine grained bedrock units in cliffs or in colluvium beneath those cliffs in grand and cataract canyons fine grained bedrock that produces debris flows contains primarily single layer clays notably illite and kaolinite and has low multilayer clay content this clay mineral suite also occurs in the colluvium that produces debris flows as well as in debris flow deposits although unconsolidated deposits have less illite than the source bedrock we investigate the relation between the clay mineralogy and major cation chemistry of fine grained bedrock units and the occurrence of debris flows on the entire colorado plateau we determined that 85 mapped fine grained bedrock units potentially could produce debris flows and we analyzed clay mineralogy and major cation concentration of 52 of the most widely distributed units particularly those exposed in steep topography fine grained bedrock units that produce debris flows contained an average of 71 kaolinite and illite and 5 montmorillonite and have a higher concentration of potassium and magnesium than nonproducing units which have an average of 51 montmorillonite and a higher concentration of sodium we used multivariate statistics to discriminate fine grained bedrock units with the potential to produce debris flows and we used digital elevation models and mapped distribution of debris flow producing units to derive a map that predicts potential occurrence of holocene debris flows on the colorado plateau

two pool to pool spacing periods on large sand bed rivers mega pools on the madeira and mississippi abstract the madeira river thalweg includes two pool to pool spacing periods first standard pool crossing sequences form 6 to 8 m deep pools these pool crossing sequences recur approximately every six channel widths 9 7 km or 6 8 w on average however the madeira study reach between manicore and porto velho in northern brazil is relatively straight making these pools more frequent than meanders second much deeper pools 13 to 30 m deep also form at relatively regular but much longer spacing 50 60 km about 40 channel widths apart the deeper mega pools occur where the river reaches the edge of the holocene alluvium encountering resistant units e g granite mud clasts and conglomerates in the confining pleistocene units these two pool scales also occur on the lower mississippi river downstream of tarbert landing this study identified pool formation processes responsible for these two pool depth and spacing scales on two large sand bed rivers the analyses computed pool statistics and correlated the deepest pools with planform controls two distinct pool formation hypotheses explain the two pool types the standard pools are rhythmic features developed by macro turbulent feedbacks while the mega pools are forced features imposed by the regional geology the former are fundamentally periodic the latter are not however periodogram analysis indicates that mega pools on the madeira form a second relatively regular pool period the regional geology including the confining pleistocene bluffs and potentially orthogonal neotectonic lineaments imposed periodic regularity to these mega pools on the madeira river that is not observed on the mississippi river a comparably sized sand bed river with mega pools

controls on pool characteristics along a resistant boundary channel abstract the north fork poudre river in phantom canyon has a pool riffle sequence formed in granitic bedrock we address two questions what controls downstream pool spacing within a pool what factors control pool dimensions we hypothesize that both pool spacing and pool geometry could be governed by available flow energy or by substrate characteristics these hypotheses were addressed using channel bed and water surface gradients surveyed under moderate flow selby rock mass strength at vertical outcrops forming lateral pool constrictions and at other vertical outcrops and joint density measured from high resolution digital images of the bedrock outcrop along each of 10 pools the downstream length between pools is quite variable documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fonten

conceptualization and classification of groundwater surface water hydrodynamic interactions in karst watersheds case of the karst watershed of the coulazou river southern france summary over the last two decades groundwater systems and surface water bodies are being more and more considered as a same entity which constitutes a single resource within the hydrologic system understanding groundwater surface water gw sw interactions is necessary to effectively manage the water resources concepts methods of analysis and classifications of these hydrodynamic interactions have thus been developed mostly in case of porous aquifer today gw sw interactions are still often poorly understood in many watersheds particularly in the case of complex aquifers like karst aquifers this study focuses on the influence of groundwater on the genesis and propagation of surface floods in the case of a highly karstified watershed gw sw hydrodynamic interactions are analysed i at a local scale focussing on hydrodynamic interactions between the karst aquifer in the vicinity of the river and the river and ii at a larger scale focussing on hydrodynamic interactions between a karst spring and sinkholes in the riverbed hydrodynamic time series are described using the karst watershed of the coulazou river western montpellier france as a case study results are used to adapt gw sw classifications that are usually devoted to porous media in case of the studied karst aquifer it is shown that the initial groundwater level may be used to forecast the type of hydraulic connection between the river and the saturated zone during flood however initial water level in the karst aquifer does not give any information about the flow direction gaining or losing stream during a flood the latter is found to be also controlled by the limited discharge capacity of karst conduits a conceptual model of karst river interactions during flood is given with concepts that are derived from the analysis of the coulazou watershed but that can be easily applied to most of the karst watersheds

predictive modelling of hydraulic head responses to dipole flow experiments in a fractured karstified limestone aquifer insights from a comparison of five modelling approaches to real field experiments summary five modelling approaches were tested against a well studied limestone aquifer constituting the hydrogeological experimental site hes of poitiers france the modelling exercise consisted of predicting the drawdown responses of a series of observation wells for two dipole pumping injection flow experiments involving two distinct well pairs at the hes the differences between model predictions appear to be mainly related to the hydraulic datasets used for model parameterisation and to a much lesser extent to the conceptual modelling approach equivalent porous medium vs discrete fracture networks the model dimensionality two dimensional vs three dimensional and or the parameterisation approach forward vs inverse despite the abundance and diversity of calibration parameterisation data all of the models failed to predict the drawdowns with a reasonable degree of accuracy only the order of magnitude of the drawdowns was correctly predicted by three of the five models whereas all models failed to predict the drawdown behaviour at both intermediate and late times the primary source of error is attributed to a lack of information in the single well pumping test data which did not capture the multi permeability structure of the aquifer as revealed a posteriori by the responses to dipole flow experiments this highlights the need to develop novel or improved approaches to characterise the hydraulic properties of limestone aquifers

history of actinide and minor element mobility in an archean granitic batholith in manitoba canada abstract surface and borehole core samples from the lac du bonnet granite manitoba canada have been analysed for major element concentrations fe 3 fe total ratios rare earth element ree content and actinide isotopic abundances this work forms part of the geological investigations of the canadian nuclear fuel waste management program performed by atomic energy of canada limited aecl the study attempts to understand the history of and processes governing mobilisation of elements and naturally occurring radionuclides during high and low temperature alteration events in fluid bearing fractures in the granite one surface sample and two core samples from 150 m and 730 m are each in contact with fractures in the granite and show evidence of alteration events that penetrated the rock matrix over distances of at least 3 cm loss of ca and na is seen in cores from a depth of 150 m from the highly altered hematite rich rock adjacent to sub horizontal fracture zones at the underground research laboratory url of aecl near lac du bonnet in contrast k fe fe 3 fe and u concentrations increase towards the fracture surface due to formation of illite and association of u with hematite and the illite at the fracture surface u continues to increase but fe and thefe 3 fe ratio decrease indicating fe removal by reduction the ree also show some enrichment in more altered rock at intermediate depths but the total ree concentration is lower than in the surface and deep core samples no clear trends are visible for parent and fracture surface ree in surface and deep core samples however disequilibrium values of 234 u 238 u and 230 th 234 u ratios in surface and intermediate depth core samples indicate that u has been mobilised in recent geological time the last ma but th has remained relatively immobile high th u and 230 th 234 u ratios in surface samples are indicative of rapid leaching of u but little isotopic fractionation probably within the last 10 5 a apparently unaltered rock several centimetres distant from the fracture in surface and intermediate depth samples has lost appreciable u but evidence from u series disequilibrium studies suggests that this process occurred more than one million years ago perhaps during deuteric or hydrothermal alteration core from a fracture at depth in the granite shows little hematite or clay formation and lacks evidence of ree and recent or ancient actinide mobilisation the u series results are correlated with the observed concentrations and isotope activity ratios of u in groundwaters sampled from the same or adjacent fractures analyses of samples of highly altered rubble recovered from centre portions of fracture zones at the url show both excesses and deficiencies of 234 u and 230 th in neighbouring locations possibly due to the presence of a redox front whose position is controlled by modern groundwater composition the implications of these results are discussed for the concept of disposal of nuclear fuel waste at depth in plutonic rock on the canadian shield

hydrogeochemical evaluation and modelling performed within the swedish site investigation programme abstract site studies for skb s swedish nuclear fuel and waste management co programme of deep geological disposal of nuclear fuel waste currently involve the investigation of two locations forsmark and laxemar simpevarp situated on the eastern coast of sweden to determine their geological hydrogeochemical and hydrogeological characteristics present work describes hydrogeochemical methods such as conceptual postglacial modelling explorative analysis mathematical modelling and construction of site descriptive models the complex groundwater evolution and patterns at forsmark and laxemar simpevarp are a result of many factors such as a the present day topography and proximity to the baltic sea b past changes in hydrogeology related to glaciation deglaciation land uplift and repeated marine lake water regressions transgressions and c organic or inorganic alteration of the groundwater composition caused by microbial processes or water rock interactions the major conclusion is that changes from glacial rebound and hence hydrogeology seems to have a major influence on the groundwater chemistry these complex data require a multidisciplinary approach to their interpretation which is based on 25 years of experience within the skb radioactive waste site investigation programme

relation between colloid composition and the environment of their formation application to the el berrocal site spain abstract in the framework of nuclear waste topics the role of colloids is more and more emphasized in relation to the transport of radioelements in natural groundwaters we attempt here to check if the nature and physico chemical characteristics of the colloids from the granitic site of el berrocal are closely related to the bedrock composition the colloids are studied in three types of groundwaters sulfate and carbonate waters in different redox conditions as well as colloidal suspensions extracted from clayey materials present in the fractures the particle size distributions are performed by photon correlation spectroscopy their chemical composition is obtained by x ray microanalysis after transversal ultrafiltration the main results deal with the chemical composition of colloids they are mainly composed of silica aluminosilicate phases and fe ti al oxyhydroxides in the case of the carbonate and oxidized hydrofacies traces of mg cu zn ba s as well as carbonate phases zn ca occur in the particular case of the sulfate hydrofacies traces of s mg cu are identified finally in the less oxidized and carbonate groundwater a lot of phases consist of sulphur with cu zn fe as well as of carbonate with cu zn fe ca and mg for the clayey suspensions colloids are mainly composed of illite and silica in conclusion the contribution of the bedrock as well as the influence of the physico chemical conditions are discussed in order to decipher the role of neoformation and dispersion processes in the colloid formation

characterisation of hydrogeological connections in a lowland karst network using time series analysis of water levels in ephemeral groundwater fed lakes turloughs summary this research has used continuous water level measurements five groundwater fed lakes or turloughs in a linked lowland karst network of south galway in ireland over a 3 year period in order to elucidate the hydrogeological controls and conduit configurations forming the flooded karstic hydraulic system beneath the ground the main spring outflow from this network discharges below mean sea level making it difficult to determine the hydraulic nature of the network using traditional rainfall spring flow cross analysis as has been done in many other studies on karst systems however the localised groundwater surface water interactions the turloughs in this flooded lowland karst system can yield information about the nature of the hydraulic connections beneath the ground various different analytical techniques have been applied to the fluctuating turlough water level time series data in order to determine the nature of the linkage between them as well as hydraulic pipe configurations at key points in order to improve the conceptual model of the overall karst network initially simple cross correlations between the different turlough water levels were carried out applying different time lags frequency analysis of the signals was then carried out using fast fourier transform analysis and then both discrete and continuous wavelet analyses have been applied to the data sets to characterise these inherently non stationary time series of fluctuating water levels the analysis has indicated which turloughs are on the main line conduit system and which are somewhat off line the relative size of the main conduit in the network including evidence of localised constrictions as well as clearly showing the tidal influence on the water levels in the three lower turloughs at shallow depths 8 km from the main spring outfall at the sea it has also indicated that the timing of high rainfall events coincident with maximum spring tide levels may promote more consistent long duration flooding of the turloughs throughout the winter

contribution of correlation and spectral analyses to the regional study of a large karst aquifer charente france the purpose of the study is to demonstrate that correlation and spectral analyses can contribute to the regional study of a large karst aquifer an example is presented for the la rochefoucauld karst aquifer charente france different types of spatially distributed time series provide valuable spatio temporal information for the karst aquifer the available time series consist of the spring flow rates the flow rates at different locations in sinking streams the piezometric levels the electrical conductivity and temperature of the water the atmospheric pressure and the precipitation the analysis of the flow rates at the springs shows that the aquifer empties very slowly and has a large storage capacity hydrodynamic links were established between three of the four rivers flowing on the aquifer and the springs the results also demonstrate the important spatial heterogeneity of the aquifer and indicate that the most rapid flow occurs in the northern part of the aquifer hourly piezometric and electrical conductivity time series indicate that the transmissivity of the aquifer varies when some conductive channels become desaturated during the low water period the delays between the distributed recharge and the piezometric level between the localized river input and the flow rates at the springs and between the electrical conductivities in rivers and the main spring provide information on the travel times in the aquifer the observation of earth tides and barometric effects indicate that this apparently unconfined aquifer has a confined behaviour

geometric adjustment of pools to changes in slope and discharge a flume experiment abstract to characterize the factors controlling pool shape 30 different forced pools were created utilizing a 50 triangular constriction in a 0 5 m wide 6 m long recirculating flume pools were scoured from an initial plane bed of sand with a d50 of 0 25 mm pool depth and length were measured and used as dependent variables in least squares multiple regression analyses discharge channel bed gradient and energy slope were the independent variables additional linear regression analyses were conducted with either pool depth or length and stream power results indicate that both pool depth and length are primarily a function of discharge channel bed and energy slopes are also significantly related to pool length but are not significantly related to pool depth stream power is significantly related to both pool depth and length but r2 values for pool depth versus discharge indicate stronger relations than those between pool depth and stream power observations on the type of geometric adjustment indicate that pools may minimize their rate of energy expenditure primarily through elongation in contrast pool depth appears to be more sensitive to the characteristics of the constrictions that create the forced pools the results suggest that many field studies may suffer from cross correlation problems in particular channel erodibility may exert a more dominant influence on pool geometry than hydraulic controls in many constriction influenced channels

effects of three gorges dam operation on spatial distribution and evolution of channel thalweg in the yichang chenglingji reach of the middle yangtze river china abstract the evolution of the channel thalweg and pool riffle sequences is a critical feature of morphological adjustments in fluvial systems and might have important effects on aquatic habitat quality channel stability and navigation based on the 220 cross sectional profiles from 2002 to 2016 residual depths and spatial statistical analyses were used to quantitatively analyse the vertical variations and longitudinal distribution of the pool riffle sequences and channel thalweg in the yichang chenglingji reach ycr of the middle yangtze river which consists of the yizhi zhijiang shashi gongan and shishou jianli sub reaches the results showed that the dramatic reduction in the sediment loads following the construction of the three gorges dam tgd has caused significant adjustments in the size morphological diversity and spatial distribution of pool riffle structures in the ycr the average depth of the pools in the yizhi zhijiang reach and the shishou jianli reach overall exhibited a nonlinear growth trend with the average residual depth increasing by 1 4 m and 1 9 m respectively however the average residual depth in the shashi gongan reach showed a decreasing trend with a reduction of approximately 1 2 m the longitudinal lengths of the riffles in all three reaches contracted to different degrees and the specific percentage of longitudinal river length occupied by riffles total riffle length total sub reach length decreased by 8 9 6 and 5 9 in the three sub reaches from upstream to the downstream in addition the morphological diversity of the thalweg elevation in the shashi gongan reach and shishou jianli reach weakened after the construction of the tgd while the bed topography in the yizhi zhijiang reach became more complex and diverse moreover the pool riffle structures in the ycr were rearranged and distributed regularly following the initiation of the tgd operation although the variation characteristics of the average pool spacing in the three sub reaches were quite different quantitative relationship between the average residual depth and the previous four year hydrological condition was proposed for the three sub reaches based on the delayed response model drm and verified using the measurements from 2013 to 2016

latest pleistocene holocene debris flow activity santa catalina mountains arizona implications for modern debris flow hazards under a changing climate abstract hazard mitigation for extreme events such as debris flows requires geologic mapping and chronologic information particularly for alluvial fans near mountain fronts in the southwestern united states in july 2006 five consecutive days of monsoonal storms caused hundreds of debris flows in southeastern arizona particularly in the southern santa catalina mountains north of tucson before 2006 no historical debris flows from the santa catalina mountains reached the populated mountain front although abundant evidence of prehistoric debris flows is present on downslope alluvial fans we used a combination of surficial geologic mapping and 10 be exposure dating to produce a debris flow history for pima and finger rock canyons the largest debris flows of latest pleistocene to early holocene age covered much of the apices of alluvial fans formed at the mouths of these canyons and extended up to 3 km downslope these debris flow deposits were inset against higher and older alluvial surfaces with few debris flow deposits of late pleistocene age the 10 be ages in this study have considerable scatter for surfaces believed to be of uniform age indicating the dual possibilities of inheritance from previous cosmic ray exposure as well as the potential for composite deposits derived from numerous debris flows we then used an empirical inundation model laharz to assess probable magnitudes of the older debris flows to evaluate possible initiation mechanisms in channel and terrace storage within the canyons is not sufficient to generate volumes likely needed to produce the larger late pleistocene to early holocene debris flow deposits the abundance of latest pleistocene and early holocene deposits suggests that large debris flows were generated during the instability associated with climate and vegetation changes at the pleistocene holocene transition under present watershed conditions with limited sediment supplies modern debris flow hazards are generally limited to within mountains and near mountain fronts

origin and mobility of humic colloids in the gorleben aquifer system the origin and mobility of humic colloids in the gorleben aquifer system have been examined for this purpose the distribution of humic colloids and relevant hydrological and geochemical parameters were examined an investigation area was selected where sediments have been disturbed by salt dome uplift and glacial events it is shown that on a local scale considerable groundwater movement and intermixing takes place from the surface down to the salt dome consequently no effective separation of groundwater layers occurs two different humic colloid sources are identified influx from the humus horizon with recharge water and continuous in situ generation via mineralization of sedimentary organic carbon soc the in situ generation leads to groundwaters with humic colloid concentrations approaching 0 4 g l compared to concentrations of less than 0 005 g l in recharge waters young groundwaters no 14c decay detected between approximately 50 and 200 m depth exhibit these highly elevated humic colloid concentrations at greater depth salt brines are found with low humic colloid concentrations this can be attributed to precipitation of humic acid and or hampering of the in situ generation process due to the high salt content there is no indication of retention or decomposition of humic colloids the fate of in situ generated humic colloids cannot be precisely evaluated due to analytical limitations and insufficient understanding of groundwater movement

sediment transport processes in pool riffle sequences this paper reviews the published data for sediment transport in pool riffle sequences which suggests that a velocity or shear stress reversal hypothesis does not explain all of the published evidence of sediment transport this conclusion is explored in more detail using observations of sediment transport from the regulated river north tyne sediment transport rates at discharges of 30 per cent bankfull are initially highest on riffles as discharge increases sediment transport rates in pools rise sharply and values locally exceed those on riffles tracing experiments using a combination of magnetic and painted tracers are used to show the downstream dispersal of fine and coarse sediments through the pool riffle sequence coarser particles experience longer transport paths and faster virtual rates of travel in pools during bankfull floods analysis of entrainment data reveals evidence for additional restraint operating on riffles and causing higher dimensionless entrainment thresholds an appraisal of the possible mechanisms controlling sediment entrainment transport and deposition in pool riffle sequences is made which reveals evidence for the operation of a combination of hydraulic sedimentological and interactive processes a descriptive model of sediment transport processes in pool riffle sequences is presented

random controls on semi rhythmic spacing of pools and riffles in constriction dominated rivers average pool spacing between five and seven bankfull widths has been documented in environments throughout the world but has limited theoretical justification in coarse bedded and bedrock environments pool formation in coarse bedded and bedrock channels has been attributed to bedrock and boulder constrictions because the spacing of these constrictions may be irregular in nature it is difficult to reconcile pool formation processes with the supposedly rhythmic spacing of pools and riffles to address these issues a simulation model for pool and riffle formation is used to demonstrate that semi rhythmic spacing of pools with an approximate spacing of five to seven bankfull widths can be recreated from a random distribution of obstructions and minimum pool and riffle length criteria it is assumed that a pool riffle couplet will achieve a minimum length based on dominant discharge conditions values for the minimum length assumption are based on field data collected in new england and california while the theoretical basis relies on the demonstrated hydraulic response of individual pools to elongation results from the simulations show that the location of pools can be primarily random in character but still assume an average spacing between four and eight bankfull widths for a variety of conditions field verification data generally support the model but highlight a highly skewed distribution of pool forming elements and pool spacing the relation between pool spacing and bankfull widths is attributed to the common geometric response of these features to dominant discharge conditions copyright 2001 john wiley sons ltd

recirculating flow and sedimentation in the colorado river in grand canyon arizona debris fans debouching into the bottom of grand canyon create rapids and flow separation in the colorado river the patterns of flow and the behavior of recirculation zones formed by flow separation are consistent throughout the canyon s length zones of recirculating flow occur along the margin of channel expansions recirculation zones are comprised of one primary eddy secondary eddies and areas of unorganized low velocity may exist upstream from the primary eddy the longest recirculation zones are formed by channel constrictions of low width to depth ratio recirculation zones increase in length with increasing discharge sand bars form beneath recirculation zones especially near separation and reattachment points reattachment bars project upstream from the reattachment point and underlie primary eddies separation bars mantle the downstream parts of the debris fans and form beneath secondary eddies and low velocity areas sediment that forms reattachment bars is dominated by sizes characteristic o

colloid facilitated transport of uranium by groundwater at the u mo ore field in eastern transbaikalia the main objective of the study is field scale analysis of colloid facilitated transport of uranium from an underground source to the biosphere as applied to safety assessment of underground repository of spent nuclear fuel snf the uranium deposit antei in eastern transbaikalia is considered as a natural analog of an underground repository of snf transport of colloid borne uranium by groundwater from the ore zone to the earth surface is examined groundwater at the uranium deposit site was sampled both in the ore zone at the depth of approximately 750 m and from the subsurface water extraction of the uranium bearing colloid from the water samples was carried out by subsequent filtration through membranes with decreasing pore size uranium concentrations in the filtrate were measured by the methods of light emitting diode induced luminescence and inductively coupled plasma mass spectrometry chemical composition of the surface of the uranium bearing colloid particles was determined by the methods of x ray photoelectron spectroscopy with ionic etching and transmission electron microscopy it is revealed that uranium bearing colloid in the ore zone and at the earth surface consists of particles of different types intrinsic colloid and pseudocolloid

stable channels with mobile gravel beds regime type equations for mobile gravel bed rivers are presented based on data obtained from 62 stable gravel bed river reaches in the united kingdom multiple regression techniques are applied to derive equations relating reach average and riffle values of width mean and maximum depth slope velocity sinuosity and riffle spacing to bankfull discharge bed and bank material characteristics valley slope bank vegetation type and an independent estimate of bankfull bed load transport rates although discharge has a dominant control on channel geometry these equations indicate that bed load discharge also has a significant influence particularly with regard to channel slope bank vegetation has a major control on width and velocity while depth velocity and slope are storngly affected by bed material size reasons for these results are considered in terms of the physical processes controlling channel adjustment the application of these regime equations is discussed and particular consideration is given to the design of sinuous channels with a pool riffle bed topograph

dynamics and contribution of karst groundwater to surface flow during mediterranean flood this paper describes the role of groundwater contribution to surface flow at the causse d aumelas a karst system near montpellier france which is traversed by an intermittent river the coulazou a first hydrologic model integrating a digital terrain model shows the inability of a standard rainfall runoff model to replicate recorded flood hydrographs while the flood peaks are routed through the karstic system along the coulazou without a phase lag the peak magnitude is somewhat modified these results indicate an initial karst system recharge followed by a significant contribution to surface flow a hydrodynamic analysis of ground water flow confirms these results the karst system first absorbs part of the rainfall which induces a general water table rise within the aquifer and then contributes to surface flow in the coulazou

dissolution in a variably confined carbonate platform effects of allogenic runoff hydraulic damming of groundwater inputs and surface groundwater exchange at the basin scale in variably confined carbonate platforms impermeable confining units collect rainfall over large areas and deliver runoff to rivers or conduits in unconfined portions of platforms runoff can increase river stage or conduit heads in unconfined portions of platforms faster than local infiltration of rainfall can increase groundwater heads causing hydraulic gradients between rivers conduits and the aquifer to reverse gradient reversals cause flood waters to flow from rivers and conduits into the aquifer where they can dissolve limestone previous work on impacts of gradient reversals on dissolution has primarily emphasized individual caves and little research has been conducted at basin scales to address this gap in knowledge we used legacy data to assess how a gradient of aquifer confinement across the suwannee river basin north central florida affected locations magnitudes and processes of dissolution during 2005 2007 a period with extreme ranges of discharge during intense rain events runoff from the confining unit increased river stage above groundwater heads in unconfined portions of the platform hydraulically damming inputs of groundwater along a 200 km reach of river hydraulic damming allowed allogenic runoff with sical 4 to fill the entire river channel and flow into the aquifer via reversing springs storage of runoff in the aquifer decreased peak river discharges downstream and contributed to dissolution within the aquifer temporary storage of allogenic runoff in karst aquifers represents hyporheic exchange at a scale that is larger than found in streams flowing over non karst aquifers because conduits in karst aquifers extend the area available for exchange beyond river beds deep into aquifers post depositional porosity in variably confined carbonate platforms should thus be enhanced along rivers that originate on confining units this distribution should be considered in models of porosity distribution used to manage water and hydrocarbon resources in carbonate rocks copyright 2013 john wiley sons ltd

fluvial geomorphology of a boulder bed debris flow dominated channel in an active tectonic environment abstract numerous streams with a drainage area of a few square kilometers draining the south flank of the santa ynez range in southern california are characterized by steep boulder bed debris flow dominated channels rattlesnake creek is a good example approximately 90 of the stored sediment in the stream valley is stable debris flow deposits found in debris flow terraces and levees adjacent to the channel the remaining 10 of stored sediment resides in the active channel where the channel morphology is dominated by large boulders 1 to 4 m in diameter derived from debris flows or rock fall that along with bedrock outcrops form rock or boulder transverse ribs with frequent step pools the dominant channel pool morphology is the step pool which accounts for most of the pools and approximately 30 of relief drop in elevation through the study reaches less common pool types identified in the study reaches include forced pools that result from convergence of flow with scour between lbres large boulder roughness elements and bedrock outcrop along the channel at near bankfull discharge the lbres and boulders in step pools armor the channel and are primary controls on channel morphology and gradient rock strength is a secondary control on channel morphology location and abundance of pools we hypothesize that step pools when inundated with sand and fine gravel from a disturbance such as wildfire during a flow event fill near bankfull stage and scour on falling stage below bankfull when unit stream power is a maximum over the step thus as with forced pools step pool maintenance depends on a specific pattern of discharge and process the process of scour during falling stage reestablishes step pools during moderate flows following disturbance

riffle pool sequences and meander morphology abstract the study is aimed at investigating the response of the riffle pool sequence to increased energy expenditure in the horizontal plane through meander development it emphasizes field measurements of riffle pool height and spacing and their links with meander morphology river reaches in southern ontario canada were surveyed and statistical relations were established between parameters describing riffle pool morphology sequence length and amplitude and planform curvature the results indicate a lengthening of the sequence with increased total angular deflection along the measured reaches further analysis suggests that this lengthening occurs in the pool as a result of meander development apparently as the path length extends beyond a critical threshold for a given bed material size the transport capacity of the sequence is compromised this may promote an initial shortening of the downstream riffle with depositional processes ultimately forming a new riffle slightly upstream to achieve a new equilibrium additional extensive data sets provided by the toronto and region conservation authority on riffle pool morphology also suggest that bed material size plays a significant role in controlling riffle pool morphology

statistical analyses and modeling approaches to hydrodynamic characteristics in alluvial aquifer this study is aimed at quantifying the difference in aquifer s response to recharge between some different locations in a fan aquifer and a delta aquifer for a preliminary study of revealing mechanisms of water transport in alluvial aquifer the aquifer s response to recharge is statistically quantified with the two viewpoints 1 timing and volume of recharge and 2 time length of aquifer s holding water for the first point a statistical model that links precipitation and groundwater level is introduced and its parameters are identified using correlation analysis our results show that the recharge rate at the toe is higher than that at the apex and at the delta for the second point the concept of memory effect of aquifer is adopted and quantified using the autocorrelation and spectral analyses our results show that the memory effect is longer at the toe of fan than at the apex and thus a temporary increase of water level has about five times as long term influence on subsequent water levels at the toe of the fan as at the apex this study demonstrates that the statistical analyses and modeling of hydrological data are useful for characterizing aquifer s hydrodynamics copyright 2012 john wiley sons ltd

groundwater flow characterization in a multilayered karst aquifer on the edge of a sedimentary basin in western france abstract on the edge of sedimentary basins burial of geological layers can involve the formation of confined karst aquifers in some cases relationships between confined and unconfined karst aquifers can exist and imply an increased difficulty in delineating contributive areas of karst system outlets with accuracy this work aims to develop a multi disciplinary approach to highlight groundwater exchanges between multilayered karst aquifers feeding a single spring toulon springs located in western france provides the opportunity to study relationships between two multilayered karst aquifers hydrograph and chemograph analysis coupled with principal component analysis pca are used to evaluate groundwater flow origins on the northern edge of a sedimentary basin natural hydrodynamic responses baseflow recession analysis auto cross correlation function show an important volume of water located in a saturated zone of the toulon karst system significant contrasts in water quality as a function of the hydrological regime flood recession and baseflow regime and comparison with shallow and deep water show the participation of a deep aquifer supporting the flow of toulon springs

the morphologic structure of step pools in mountain streams abstract step pool sequences in streams in the santa monica mountains of southern california impart a characteristic morphologic structure that varies with slope but despite the strong association with slope that suggests a direct process control analysis of 464 step pools in 13 study reaches reveals the relationship to reflect correlation but not necessarily causality the direct control on step height is particle size whereas discharge is the probable causal process determining step wavelength because both particle size and discharge generally change with channel slope downstream a slope variation with step wavelength and height is the apparent indirect geometric result a conceptual model of process form linkages is proposed based on these results whereby the step pool morphology is produced by positive relationships between wavelength and discharge and between height and particle size the model offers new insights for explaining the step pool morphology and it is potentially useful in channeling future efforts toward the appropriate scales and variables

flood events in mediterranean ephemeral streams ramblas in valencia region spain abstract this article deals with flood events in mediterranean ephemeral streams typical of the valencia region the combination of the basin physical characteristics steep slopes sparse vegetation thin soils and permeable rock and intense heavy and irregularly distributed rain generates flash floods runoff generation is sudden giving rise to flash floods with sharp narrow hydrographs with short time lags the high amount of runoff is nevertheless only a small fraction of the total rainfall since the characteristics of the river basins are such that infiltration of large amounts of water occurs using daily hydrological data from the rambla de la viuda basin and 5 min data from both the barranc del carraixet and the rambla de poyo basins the rainfall runoff processes have been analysed during flood events in these ephemeral streams

linear model describing three components of flow in karst aquifers using 18o data the stable isotope of oxygen 18o is used as a naturally occurring ground water tracer time series data for 18o are analyzed to model the distinct responses and relative proportions of the conduit intermediate and diffuse flow components in karst aquifers this analysis also describes mathematically the dynamics of the transient fluid interchange between conduits and diffusive networks conduit and intermediate flow are described by linear systems methods whereas diffuse flow is described by mass balance methods an automated optimization process estimates parameters of lognormal pearson type iii and gamma distributions which are used as transfer functions in linear systems analysis diffuse flow and mixing parameters also are estimated by these optimization methods results indicate the relative proximity of a well to a main conduit flowpath and can help to predict the movement and residence times of potential contaminants the three component linear model is applied to five wells which respond to changes in the isotopic composition of point recharge water from a sinking stream in the madison aquifer in the black hills of south dakota flow velocities as much as 540 m d and system memories of as much as 71 years are estimated by this method also the mean median and standard deviation of traveltimes time to peak response and the relative fraction of flow for each of the three components are determined for these wells this analysis infers that flow may branch apart and rejoin as a result of an anastomotic or channeled karst network

time variant cross correlation to assess residence time of water and implication for hydraulics of a sink rise karst system 1 transport rates and residence time in the subsurface are critical parameters for understanding water rock interactions for efficient contaminant remediation this paper presents a methodology for assessing flow and transit time of water through hydrological systems with specific applications to karst systems and implication for hydraulics of a conduit system surrounded by a porous and permeable intergranular matrix a time variant cross correlation function analysis is applied to bivariate time series that characterize mass transfer assuming a stationary system using sliding windows of various sizes we apply the method to 1 year long temperature records in the santa fe river north central florida measured at 1 the river sink where all the incoming surface water drains into a sinkhole 2 sweetwater lake where the river resurges into a 500 m long karst window and 3 the river rise where the water discharges from a first magnitude karst spring results are compared with those obtained using specific conductivity estimated residence time ranges from less than 1 day during floods to more than 15 days during base flow within the 8000 m flow path between the river sink and the river rise results are used to characterize geometric hydraulic and hydrodynamic properties of this sink rise system with strong matrix conduit interactions these properties are critical to the chemical and physical behavior of surface water groundwater mixing our results also have direct implications for sampling strategies and hydrograph separation of many karst systems with different degrees and types of matrix porosity and permeability

aquifer response to stream stage and recharge variations ii convolution method and applications abstract in this second of two papers analytical step response functions developed in the companion paper for several cases of transient hydraulic interaction between a fully penetrating stream and a confined leaky or water table aquifer are used in the convolution integral to calculate aquifer heads streambank seepage rates and bank storage that occur in response to stream stage fluctuations and basinwide recharge or evapotranspiration two computer programs developed on the basis of these step response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream aquifer systems in the northeastern and central united states these applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank hydraulic properties recharge rates streambank seepage rates and bank storage analysis of the water table aquifer adjacent to the blackstone river in massachusetts suggests that the very shallow depth of water table and associated thin unsaturated zone at the site cause the aquifer to behave like a confined aquifer negligible specific yield this finding is consistent with previous studies that have shown that the effective specific yield of an unconfined aquifer approaches zero when the capillary fringe where sediment pores are saturated by tension extends to land surface under this condition the aquifer s response is determined by elastic storage only estimates of horizontal and vertical hydraulic conductivity specific yield specific storage and recharge for a water table aquifer adjacent to the cedar river in eastern iowa determined by the use of analytical methods are in close agreement with those estimated by use of a more complex multilayer numerical model of the aquifer streambank leakance of the semipervious streambank materials also was estimated for the site the streambank leakance parameter may be considered to be a general or lumped parameter that accounts not only for the resistance of flow at the river aquifer boundary but also for the effects of partial penetration of the river and other near stream flow phenomena not included in the theoretical development of the step response functions

the challenge of modeling pool riffle morphologies in channels with different densities of large woody debris and boulders studies on pool morphologies include reports of over 80 or 90 of pools being associated with structural controls and large obstructions that include boulders bedrock outcrops and large woody debris lwd a monte carlo simulation approach and developmental computer model was created to predict pool formation spacing and the percentage length covered by pools riffles scour holes and runs based on input data that include channel slope width the number of small and large boulders and the number of 10 30 cm 30 60 cm and 60 cm pieces of wood the statistical empirical model is founded on the idea that boulders bedrock outcrops and large woody debris provide a physical framework that then controls local water surface slopes velocity patterns and the locations of pools and riffles the spacing values of individual types and sizes of obstructions are modeled as log normal distributions with separate distributions for each obstruction type pools are assigned different probabilities of development depending on the obstruction type pool and riffle lengths used to create the subsequent morphology follow their own slope dependent log normal trends a minimum distance develops between successive pools because of the backwater and turbulent conditions needed for pool formation the total number and spacing of pools riffles and scour holes thus reflects the number and locations of obstructions and characteristics of the pool riffle couplet the simulation model accurately captures the number of pools in the modeled data range at 65 of all the verification field sites and 86 of the verification field sites with a more limited range of width and slope characteristics lower levels of prediction capabilities are associated with modeled numbers of scour holes and log jams the model accurately mimics some statistical attributes of pool spacing and future versions of the model could be developed to improve overall predictive capabilities copyright 2011 john wiley sons ltd

the influence of pool length on local turbulence production and energy slope a flume experiment the in uence of pool length on the strength of turbulence generated by vortex shedding was investigated in a 6 m long recirculating ume the experiment utilized a 38 constriction of ow and an average channel bed slope of 0 007 the base geometry for the intermediate length pool experiment originated from a highly simpli ed 0 10 scale model of a forced pool from north saint vrain creek colorado discharge in the ume was 31 6 l s which corresponds to a discharge in the prototype channel of 10 m3 s three shorter and four longer pool lengths also were created with a xed bed to determine changes in turbulence intensities and energy slope with pool elongation three dimensional velocities were measured with an acoustic doppler velocimeter at 31 40 different 0 6 depth and near bed locations downstream of the rectangular constriction the average velocity and root mean square rms of the absolute magnitude of velocity at both depths are signi cantly related to the distance from the constriction in most pool locations downstream of the constriction in many locations pool elongation results in a non linear change in turbulence intensities and average velocity based on the overall ow pattern the strongest turbulence occurs in the center of the pool along the shear zone between the jet and recirculating eddy the lateral location of this shear zone is sensitive to changes in pool length energy slope also was sensitive to pool length due to a combination of greater length of the pool and greater head loss with shorter pools the results indicate some form of hydraulic optimization is possible with pools adjusting their length to adjust the location and strength of turbulent intensities in the center of pools and lower their rate of energy dissipation copyright 2004 john wiley sons ltd

hydrogeological processes in a fluviokarstic area inferred from the analysis of natural hydrogeochemical tracers the case study of eastern serrania de ronda s spain in riverine karst areas surface water interacts with the groundwater flowing through carbonate aquifers understanding the interference of water fluxes in this type of environments is essential to effectively manage the groundwater resources particularly in areas where karst aquifers comprise the main source of drinking water in this research the interaction between surface water and groundwater in the turon river valley eastern serrania de ronda s spain and the functioning of sierra blanquilla karst aquifer have been characterised by means of hydrodynamic monitoring and the combined use of physical chemical parameters and natural hydrogeochemical tracers the results show connected gaining streams in the river stretches close to the permanent springs while in the surroundings of the overflow springs the river reaches behave as gaining high flow and as perched losing low flow soil natural tracers permit tracing runoff arising from the upper part of the hydrological watershed via river which interacts with the groundwater drained in the main discharge area of the aquifer furthermore the analysis of hydrogeochemical data and chemographs demonstrate that sierra blanquilla aquifer behaves as a typical conduit flow system in which the unsaturated zone predominantly participates during high flow periods while the saturated zone is more active in low flow when the groundwater inputs maintain the turon river discharge the more detailed understanding of how the hydrogeochemical characteristics of groundwater vary over time and space has direct consequences on karst spring protection and in the environmental preservation of groundwater ecodependent systems

mediterranean flash flood transfer through karstic area karstic aquifers influence flash floods propagation in mediterranean countries near montpellier southern france discharge data are recorded on the coulazou river upstream and downstream of the aumelas causse two gauging stations are used to describe the hydrodynamics of this binary karstic system the first station characterizes the non karstic catchment area the second one is representative of the karstic part of the watershed records since april 2004 are used to understand how the river interacts with a karstic aquifer hydrograph analysis of three flash flood events is described corresponding discharge time series recorded at the two gauging stations are used to describe the modification of the hydrographs by auto and crosscorrelations analyses finally linear system analyses are used to provide the transfer functions of this binary karstic system according to the three flood events characteristics initial conditions volume spatial distribution of rainfall etc theses functions summarize the hydrodynamic behaviour of the system their shapes are indicative of the dynamics of the storage the release and the contribution to surface waters

relationships between land use and forced pool characteristics in the colorado front range abstract land use practices in colorado during the last two centuries altered the supply of sediment and water to many channels in the upper south platte basin as a result of increased supply of sediment and mobility and reduced peak flows the characteristics of pools associated with channel constrictions referred to as forced pools may have been altered increased supply of sediment and reduced transport capacity of high flows could lead to aggradation in forced pools channel confined by road corridors could lead to high velocities at normal flows increased energy dissipation from riprap or even increased pool frequency resulting from failed riprap to assess potential alterations four hypotheses were tested 1 impacted streams will show significantly different mean volume of pools than a control stream 2 mean volume of pools on streams where land use activities increased the supply of sediment will be significantly different from streams solely affected by flow regulation 3 the strongest change in characteristics of pools of impacted streams will be a reduced volume of pools 4 streams affected by road corridors will show statistically lower spacing of pools than streams unaffected by roads the downstream spacing and residual volume of twenty consecutive forced pools were surveyed on five streams in the colorado front range that varied from no contemporary impact to multiple historical and contemporary impacts ancova with stepwise model selection indicated that degree of land use categorical bankfull spacing of pools upstream riffle slope and expansion ratio were all significant 0 1 predictors of volume of pools r 2 0 73 simple linear regression of mean volume of pools and stream specific variables gradient drainage area and discharge and least square means comparison of mean volume of pools indicated a need to standardize volumes of pools by slope and discharge so that the volumes of pools could be compared among different levels of land use significant correlations between drainage area and volume of pools allowed volume of pools to be standardized by drainage area and thereby discharge this dimensionless variable was also significantly correlated with channel slope which permitted the construction of a new variable pv qs volume of pools standardized by discharge and slope least square means comparison of mean pv qs revealed that the control reach was significantly different from road impacted reaches mean volume of pools was significantly larger in the control reach compared to all but one road impacted stream this was likely a function of higher wood loading in the control reach and the competence of high flows in the road impacted reach streams affected by road corridors did not have significantly different bankfull spacing of pools from streams not impacted by roads the multiple interactions among control and response variables explored in this study indicate the need to identify the most constrained and sensitive response variables when attempting to assess channel response to land use

spatiotemporal landslide detection for the 2005 kashmir earthquake region abstract various scientists forecasted long term major slope failures after the 8 october 2005 7 6 mw earthquake in the northern parts of pakistan along the balakot bagh fault line the earthquake destabilized numerous slopes by creating a large number of tension cracks which may lead together with the monsoonal climatic conditions to increased landslide activity to test these forecasts an area of 36 km2 was selected in which changes in landslide activity area and types were quantified after each monsoon season for the following consecutive three years on screen stereo interpretations of high spatial resolution satellite imagery were carried out together with field investigations to identify landslide types and to quantify their changes in the area the landslide inventory showed that 158 landslides were triggered along the balakot bagh fault line the most abundant type of active landslide was translational which was mainly concentrated along the fault line in the muzaffarabad formation landslide activity was very high for a period of two years at maximum after which the majority of the slopes gained a state of stability in contrast to the predictions of long term extensive landslide activity slopes started re vegetating and landslide activity decreased within two years after the earthquake

effects of aggradation and degradation on riffle pool morphology in natural gravel channels northwestern california after the flood of december 1964 12 gaging sections in northern california widened as much as 100 and aggraded as much as 4 m and then degraded to stable levels during a period of 5 years or more as channels aggraded bed material became finer and low to moderate flow through gaging sections in pools became shallower faster and steeper comparisons of longitudinal profiles also show the diminishment of pools as well as a decrease in bar relief accompanying the excessive sediment load as gaging sections degraded hydraulic geometries recovered to a limited degree full recovery probably depends on channel narrowing and further depletion of sediment supply the hydraulic changes with aggradation indicate an increase in the effectiveness of moderate discharges less than i to 2 year recurrence interval annual flood series to transport bed load and shape the bed bars become smaller pools preferentially fill and rimes armored with relatively small gravel tend to erode headward during falling stages and form a gentler gradient excess sediment can thus be more readily transported out of channels when additional contributions from watersheds are usuall slight

morphology of riffle pool sequences in the river severn england despite the occurrence of pool riffle sequences in many rivers there are few data concerning pool riffle unit morphology of many criteria proposed to identify pool riffle units only two methods can be regarded as objective and robust these are the zero crossing and the control point methods in this paper statistics are developed from the zero crossing method to describe the streamwise morphology of 275 riffles and 285 pools which form a near continuous 32 1km of the bed of the river severn in shropshire england yalin s theoretical relationship between pool riffle unit length i p and channel width w i p 3w applies to the river severn reach average riffle height h is a constant proportion of bankfull depth h typically h i 0 16h riffle height is a positive function of riffle length pool depth is a positive function of pool length however both riffle length and pool length increase more rapidly than the bed level amplitude such that long riffles or pools are relatively flat as channel gradient reduces bedforms flatten and become more asymmetric as riffle stoss sides and the proximal slope of pools lengthen at the expense of riffle lee sides and pool distal slopes the statistical relationships between riffle height length and water depth are similar to those for equilibrium subaqueous dunes the severn data are partially consistent with yalin s theoretical analysis relating riffle bedform length lr to water depth i e lr i i2i h wherein i i i 1 for steep near equilibrium bedforms but i i i 2 to 3 as the relative depth decreases and riffles become long low features a consideration of turbulence data indicates that the frequency of coherent turbulent flow structures associated with the riffle pool mixing length is of the order of 60 seconds the morphological and dynamic similarity of the river severn riffles with dunes raises intriguing questions with respect to self similar convergent organization of periodic alluvial bedforms and to bedform dynamic classification particularly

debris fan reworking during low magnitude floods in the green river canyons of the eastern uinta mountains colorado and utah the magnitude and frequency of tributary debris flows and the historical range of main stem river discharges are the main factors that create and modify rapids in the colorado river system monitoring of two recently aggraded debris fans in the green river canyons of the eastern uinta mountains shows that main stem floods with magnitudes between 40 and 75 of the predam 2 yr flood cause significant reworking of fan deposits cutbanks formed at fan margins during both small and large flows indicating that lateral bank erosion is an important reworking mechanism armoring of the debris fan surface limited the degree of reworking by successive floods even when subsequent flood magnitudes were similar to those that caused significant reworking peak discharges increased the width of the reworked zone decreased fan constrictions and lowered the water surface elevation of the ponded backwater contrary to predam geomorphic evidence monitoring indicated that eroded material from recently aggraded debris fans was deposited in bars adjacent to the downstream parts of both fans this change in the organization of the fan eddy complex has the potential to alter the location of recirculating eddies and associated areas of fine grained sediment deposition and storage

geology and geophysics of the underground research laboratory site lac du bonnet batholith manitoba the lease area of the atomic energy of canada limited underground research laboratory covers 3 8 km2 and is located 2 5 km north of the south contact of the lac du bonnet batholith a shaft to 255 m and 130 boreholes up to 1100 m deep expose the third dimension the underlying granite is largely of two types i pink porphyritic which may be biotite rich gneissic and or xenolithic and ii grey homogeneous and equigranular composition layering including xenolith rich zones outlines domes along an antiform trending north northeast through the western part of the lease area the southeast dipping flank underlies the eastern half of the site including the shaft axes of folding trend 065 and 140 homogeneous grey granite being relatively fresh and unfractured is associated with a magnetic field that is about 100 nt higher and with a resistivity that is up to 5000 m higher than those of other units a pattern of highs in the magnetic field caused by the high magnetite content of some xenolith

formation of riffle pool sequences field evidence for an autogenetic process abstract riffle pool sequences are the characteristic reach scale bedforms of mixed and gravel bedded rivers while most research has been directed to the quantitative description of these sequences and to their maintenance comparatively little attention has been given to the processes responsible for their formation in this paper field results from quasi continuous velocity records obtained with an array of electro magnetic current meters are analysed with respect to a model of macro scale structure in the turbulent velocity field of natural channels this model has been suggested as the most plausible basis for riffle pool formation the results demonstrate the occurrence of a variety of coherent flow structures some of which scale on channel dimensions as predicted by the model but which also suggest that some revision of the association between flow structure and riffle pool formation is necessary it is suggested that riffle pool units are initiated with the generation of roller eddies upstream and downstream from a major flow obstacle corresponding to engineering criteria for scour around bridge piers the obstacle persists long enough to fix the flow pattern and hence account for significant modification of channel form but is ultimately removed as part of the process of bed modification via the extension of scour three distinct stages in the process are involved local scour of a single pool creates deposition downstream which then generates the next downstream flow irregularity a riffle pool sequence is thus created autogenetically as the summation of a sequence of irregularities each unit of which is formed and maintained only by flow dynamics operating at the local scale the process is essentially both deterministic and statistical in character it is further suggested that spatial differences in the near bed turbulence field arising from incipient riffle pool topography themselves create differences in surface sediment entrainment which enhance and maintain the sequence in a form process feedback mechanism similar reasoning might possibly be extended to the entire range of bedform sizes

pool fills a window to palaeoflood history and response in bedrock confined rivers channel scale sedimentary units associated with bedrock controlled riffle pool morphology are examined in detail along sandy creek gorge an ephemeral stream in arid south eastern central australia pool fills comprise cut and fill assemblages of poorly sorted sediments ranging in texture from muds to boulders five unit types are defined based on particle size sedimentary structures geometry and bounding surface character 1 coarse grained bar platform 2 fine grained bar supraplatform 3 fine grained pool fill 4 fine grained bench and 5 modern pool fill the last coarse grained unit currently lining the pools suggests an altered sedimentation style over the post settlement period post ad 1860s situated at bedrock valley constrictions pool fills are compared with other sedimentary units associated with recirculating currents eddy bars and slackwater deposits but only the fine grained bench units reflect eddy recirculation the pool fills are principally forced bars associated with bedrock controlled or forced riffle pool morphology a late holocene palaeoflood history is proposed based on radiocarbon ages from the pool fills multiple phases of cut and fill activity were preceded by a superflood 3400 1900 years ago that eroded the pool fills to bedrock the resilience of the pool fills was illustrated by the passage of a 1 in 100 year flood in 1992 which caused only minor erosion the presence of pool fills may provide a window to past phases of river activity that cannot be extracted from either historical records observations or palaeoflood slackwater sediment analyses the formation and sedimentary preservation potential of these landforms reflect a combination of hydraulic and structural influences but the occurrence of high magnitude floods exerts the dominant control

paleohydrology of pool and riffle pattern development boulder creek utah the low flow channel morphology of boulder creek is characterized by a well developed pool and riffle pattern the riffles consist of accumulations of basaltic boulders deposited from upstream source areas during extremely large flows paleoflood water surface profiles defined by high water indicators such as slack water sediments and silt lines indicate that discharges of up to 400 50 m 3 s have affected the lower reaches of this bedrock stream system stratigraphic relationships and archaeologic and radiometric age constraints indicate that at least four large magnitude low frequency flow events have occurred within the past 500 to 1 000 radiocarbon years b p step backwater hydraulic reconstructions of these large flows suggest that the positions of the boulder comprised riffles are controlled by spatial variations in large flow stream power boulder deposition occurs where channel stream power drops below critical power thresholds necessary for boulder transport high discharge stream power minima occur in reaches immediately upstream of canyon bends and constrictions and downstream of canyon expansions the low flow riffles occur at these sites comparison of calculated stream power values and measured boulder sizes with established coarse particle transport relationships indicates that a 400 m 3 s flow is approximately the minimum discharge competent to affect this pool and riffle pattern

time series analyses for karst river interactions assessment case of the coulazou river southern france summary in many karst systems throughout the world numerous karst features facilitate the exchange of water between the surface the vadose zone and the saturated zone of the aquifer these interactions play actually a prominent role in the ground and surface waters circulation this study aims at assessing karst river interactions by the way of flood hydrograph analysis and new tools for time series analysis in this field of research as in many others binary karst system the captured waters of the coulazou river travel through conduits and preferential flow paths in the vadose zone and join the saturated zone of the aquifer this river is an ephemeral river in a mediterranean context where rapid and intense floods occur each year this hydrologic behaviour is appropriate to study the transfer of a flood through a karst area the water level in caves the rainfall all over the karst aquifer catchment area the piezometric level within the karst aquifer and the discharge in the river upstream and downstream of the karst aquifer are measured in order to understand the karst river exchanges during a flood the modification of the surface flows in the river is treated as a linear time invariant system lti system correlation and spectral analyses are used to understand how the lti system dissipates or enhances the flood wave energy for several floods the frequency response function estimations are interpreted in term of flood wave modification through the karst area in this way according to the initial state of the karst river system the autogenic and or allogenic recharge of the aquifer may induce surge flows and a significant karst contribution to surface flows