a meteorological analysis of the 2013 alberta flood antecedent large scale flow pattern and synoptic dynamic characteristics abstractthe 19 21 june 2013 alberta flood was the costliest cad 6 billion natural disaster in canadian history the flood was caused by a combination of above normal spring snowmelt in the canadian rockies large antecedent precipitation and an extreme rainfall event on 19 21 june that produced rainfall totals of 76 mm in calgary and 91 mm in the foothills as is typical of flash floods along the front range of the rocky mountains rapidly rising streamflow proceeded to move downhill eastward into calgary a meteorological analysis traces an antecedent rossby wave train across the north pacific ocean starting with intense baroclinic development over east asia on 11 june subsequently downstream rossby wave development occurred across the north pacific a 1032 hpa subtropical anticyclone located northeast of hawaii initiated a southerly atmospheric river into alaska which contributed to the development of a cutoff anticyclone over alaska and a rex block ridge to the north cyclone to the south in

transporting capacity of overland flow on plane and on irregular beds in this paper the transporting capacity of thin flows in the laminar and transitional flow regime is studied experiments were carried out on irregular as well as on plane beds using two totally different set ups the results of these two types of experiment were convergent in both cases sediment concentration was clearly related to grain shear velocity and unit stream power expressed as the product of mean velocity and slope yang 1973 the data agreed with those of kramer and meyer 1969 for a sandy bed the unit stream power relationship was able to predict reasonably well the sediment concentrations measured on a mulched surface for laminar and transitional flows both the unit stream power and the shear velocity are related in the same way to slope and unit discharge the unit stream power is a parameter which in particular can be very easily measured and might therefore become useful in obtaining a quick estimate of the transporting capacity of a thin flow however before a sediment transport equation for thin flows can be developed more information is needed about the influence of the flow regime and grain size and density

investigating transport properties and turbidity dynamics of a karst aquifer using correlation spectral and wavelet analyses in many places throughout the world drinking water is frequently contaminated by turbidity such turbidity however as representative of particle transport can be used as to trace certain features of particle transport properties in order to investigate the relation between particle and dissolved species transport and hydrodynamics in karst systems correlation and spectral analyses were performed on time series of rainfall input signal and water level specific conductance and turbidity output signals at a karst spring system in the chalk aquifer of the lower seine valley france this system is composed of a spring connected to a sinkhole on the chalk plateau where a small creek enters the subsurface the autocorrelation functions for water level and turbidity showed a short memory effect demonstrating the short duration of the influence of flood events on these two parameters whereas specific conductance representing less mineralized storm derived water had a much longer memory effect these results were interpreted as reflecting the rapid reactivity of the spring to rain events with storage of water in the fissured chalk explaining the longer memory effect for specific conductance than for particles energy spectra computed by fast fourier transform of autocorrelation functions showed a strong structure in the output signals whereas the input signal rainfall was random thus allowing assessment and comparison of system behaviour regarding dissolved and solid transport as well as hydraulics cross correlation functions which allow an assessment of impulse response functions confirmed the low inertia of the system for water level and turbidity and the much higher inertia for specific conductance in addition to the main peak two secondary peaks in the cross correlation functions suggest the existence of additional flowpaths that might involve the contribution of other point source recharge and or delayed infiltration through the clayey surficial formation and solution pipes which could act as epikarst analysis using continuous wavelet spectra allowed a better investigation of the rainfall signal structure and highlighted a strong relationship between turbidity and rainfall which could not be deduced from the energy spectra specific spectral components in water level were isolated and a time domain reconstruction using inverse wavelet transform allowed separation of quick flow and slow flow components

a 1 d morphodynamic model for rill erosion 1 the key objective of this paper is to develop a 1 d hydrodynamic and sediment transport model namely rill1d that handles transcritical flows over abrupt changes e g formation of pool crests and width change in a single rill and also predicts changes in rill bed elevation replication of rill conditions in terms of flow and bed evolution changes necessitated the use of an enhanced tvd maccormack scheme with implementation of tseng s surface gradient method to provide an oscillation free solution over formed pool crests the model at the end of each time step calculates the flow depth velocity and bed shear stress and provides changes in bed elevation and grain size distribution within a cell the hydrodynamic performance of rill1d is evaluated by comparing its results with either analytical solutions or experimental observations from various benchmark tests with rigid bed conditions that include 1 formation of a hydraulic jump in a rectangular channel 2 steady subcritical and transcritical flow without a shock over a hump 3 formation of a hydraulic jump in a converging diverging frictionless channel and 4 flows over step pools it is shown that the enhanced tvd maccormack scheme adequately simulates transcritical flows by preserving the mass conservation and reducing the artificial numerical error the scheme also approximates satisfactorily depth and velocity for a single rill with a fixed bed consisting of steps and pools except near the pool headwalls where a backroller forms with negative velocities the sediment component of rill1d is evaluated by two field investigations of single rills with mobile beds with the field data the code is tested for its ability to reproduce measured values of sediment transport rates a sensitivity analysis is performed to assess the effects of cell size and critical erosional strength in the predictive ability of the model rill1d performs reasonably well in these simulations in terms of sediment prediction rates and fared adequately in terms of replicating rill bed morphology

field investigation of rill and ephemeral gully erosion in the sparacia experimental area south italy abstract this paper reports the results of a field investigation aiming at characterizing the morphology and hydraulics of both rills and ephemeral gullies egs monitored at sparacia experimental area sicily italy the comparison between rill and interrill erosion measurements showed that sediment delivery processes occurred in some erosive events and that the rill erosion rate was dominant in many cases the measurements were used for testing both the empirical relationships between the channel rill egs and gully length and its eroded volume and among the morphological variables length width depth and volume describing the channelized process finally the rill and egs hydraulic geometry was modelled by three well known power equations relating the discharge with the mean flow velocity with the flow depth and with the width of each channel segment respectively the rill measurements also showed that the flow velocity was affected by the rill segment slope while the flow depth and width were controlled by the plot slope therefore three equations taking into account these slope effects were proposed to estimate the hydraulic characteristics of the rills monitored at the sparacia area

comparison of rill flow velocity regimes between developing and stationary rills abstract flow velocity is fundamental in calculating related parameters of physical soil erosion models it has been well known that rill flow velocity varies with developing rill form which complicates and impedes the development of soil erosion models in filed rainfall erosion frequently occurs with pre existing rills not damaged by tillage practices however the rill flow velocity in this case has received little attention in this study we investigated rill flow velocity regimes for both developing and stationary rills using 5 m length plots in the laboratory the experiments included two consecutive rainfalls which had similar runoff rate the first rainfall had an intensity of 90 mm h 1 which generated well developed rills the second had an intensity of 60 mm h 1 and did not damage the rills formed by the first rainfall the results show that for a developing rill rill flow velocity is higher in the lower slope than that in the upper slope and rill flow velocity in the lower slope fluctuates much more over time as a result of the variation of rill morphology following rill development with rill development the rill flow velocity of the lower slope decreased responding to the stabilizing rill channel and exhibited a similar trend to that in upper slope for a stationary rill the rill flow velocities at both sections varied little over time demonstrating that rill flow velocity is primarily influenced by rill morphology hence the results suggested that the strength of fluctuation in rill flow velocity could be used to characterize the instantaneous intensity of soil erosion and active level of rill development the channel of the stationary rill simply acted as transport pathways of sediment supplied by inter rill erosion the physical models of soil erosion should take into account the micro topography on land surface related to the antecedently formed rills

processes controlling the structure and longevity of two quasi linear convective systems crossing the southern new england coast abstractthis paper explores the structural evolution and physical processes that explain the modification of two quasi linear convective systems qlcss that encountered the densely populated new york city atlantic coastal region one qlcs on 31 may 2002 traversed the atlantic coastal boundary with little change in its intensity producing widespread severe wind damage across new york city and long island during this event warm air advection at 925 hpa helped destabilize the layer above this level over the coastal zone while the marine boundary layer deepened below this level the 0 3 km line perpendicular vertical wind shear was relatively strong which supported ascent along the leading edge of the diabatically generated cold pool the surface based convective system became slightly elevated as it moved over the marine waters in contrast the 23 july 2002 qlcs decayed upon encountering the atlantic coastline despite its coincidence with a surface cold front the most unstable cape values during thi

temporal scaling of hydraulic head and river base flow and its implication for groundwater recharge 1 spectral analyses were conducted for hourly hydraulic head h data observed over a 4 year period at seven monitoring wells in the walnut creek watershed iowa the log power spectral density of the hydraulic head fluctuations versus log frequency f at all seven wells is shown to have a distinct slope or fractal dimension d indicating temporal scaling in the time series of water level fluctuations the fractal dimension of the time series varies from well to well and the spectrum for the average h over all seven wells has a fractal dimension of 1 46 and hurst coefficient of 0 54 the log power spectral density of estimated base flow in the walnut creek and four other watersheds versus log f is shown to have two distinct slopes with a break in scaling at about 30 days it is shown that the groundwater recharge process in a basin can be estimated from a head spectrum based on existing theoretical results hydraulic head in an aquifer may fluctuate as a fractal in time in response to either a white noise or fractal recharge process depending on physical parameters i e transmissivity and specific yield of the aquifer the recharge process at the walnut creek watershed is shown to have a white noise spectrum based on the observed head spectrum

organization and environmental properties of extreme rain producing mesoscale convective systems this study examines the radar indicated structures and other features of extreme rain events in the united states over a 3 yr period a rainfall event is defined as extreme when the 24 h precipitation total at one or more stations surpasses the 50 yr recurrence interval amount for that location this definition yields 116 such cases from 1999 to 2001 in the area east of the rocky mountains excluding florida two kilometer national composite radar reflectivity data are then used to examine the structure and evolution of each extreme rain event sixty five percent of the total number of events are associated with mesoscale convective systems mcss while a wide variety of organizational structures as indicated by radar reflectivity data are seen among the mcs cases two patterns of organization are observed most frequently the first type has a line often oriented east west with training convective elements it also has a region of adjoining stratiform rain that is displaced to the north of the line the second type has a back building or quasi stationary area of convection that produces a region of stratiform rain downstream surface observations and composite analysis of rapid update cycle version 2 ruc 2 model data reveal that training line adjoining stratiform tl as systems typically form in a very moist unstable environment on the cool side of a preexisting slow moving surface boundary on the other hand back building quasistationary bb mcss are more dependent on mesoscale and storm scale processes particularly lifting provided by storm generated cold pools than on preexisting synoptic boundaries

moist dynamics and orographic precipitation in northern and central california during the new year s flood of 1997 abstract the dynamics of moist orographic flows during the january 1997 floods in northern and central california are investigated using numerical simulations computed with the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 early in the event 31 december 1996 1 january 1997 the low level winds offshore of california s central coast were blocked by the topography of the santa lucia range and the low level winds in the central valley were blocked by the topography of the central sierra nevada range in contrast moisture laden winds along the northern coast ranges and the northern sierra nevada flowed over topographic barriers as the core of humid air migrated to the south over 24 h the low level barrier jets weakened as the atmospheric stability decreased bringing heavy rainfall to the central and southern sierra nevada at the end of the event the heavy precipitation during this event was largely controlled by the interactio

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

using tropopause maps to diagnose midlatitude weather systems the use of potential vorticity pv allows the efficient description of the dynamics of nearly balanced atmospheric flow phenomena but the distribution of pv must be simply represented for ease in interpretation representations of pv on isentropic or isobaric surfaces can be cumbersome as analyses of several surfaces spanning the troposphere must be constructed to fully apprehend the complete pv distribution following a brief review of the relationship between pv and nearly balanced flows it is demonstrated that the tropospheric pv has a simple distribution and as a consequence an analysis of potential temperature along the dynamic tropopause here defined as a surface of constant pv allows for a simple representation of the upper tropospheric and lower stratospheric pv the construction and interpretation of these tropopause maps which may be termed isertelic analyses of potential temperature are described in addition techniques to construct dynamical representations of the lower tropospheric pv and near surface potential temperature which complement these isertelic analyses are also suggested case studies are presented to illustrate the utility of these techniques in diagnosing phenomena such as cyclogenesis tropopause folds the formation of an upper trough and the effects of latent heat release on the upper and lower troposphere

numerical simulations of the 2013 alberta flood dynamics thermodynamics and the role of orography abstractthe 19 21 june 2013 alberta flood was the second costliest 6 billion cad natural disaster in canadian history trailing only the 2016 fort mcmurray alberta canada wildfires one of the primary drivers was an extreme rainfall event that resulted in 75 150 mm of precipitation in the foothills west of calgary canada here the mesoscale dynamics and thermodynamics that contributed to the extreme rainfall event are elucidated through high resolution numerical model simulations in addition terrain reduction model sensitivity experiments using gaussian smoothing techniques quantify the importance of orography in producing the extreme rainfall event it is suggested that the extreme rainfall event was initially characterized by the formation of a surface cyclone on the eastern side of the canadian rockies due to quasigeostrophic qg mechanisms orographic processes and diabatic heating feedbacks maintained the surface cyclone throughout the event extending the duration of both easterly upslope

the value of a physically based model versus an empirical approach in the prediction of ephemeral gully erosion for loess derived soils abstract a data set on soil losses and controlling factors for 58 ephemeral gullies has been collected in the belgian loess belt from march 1997 to march 1999 of the observed ephemeral gullies 32 developed at the end of winter or in early spring winter gullies and 26 ephemeral gullies developed during summer summer gullies the assessed data have been used to test the physically based ephemeral gully erosion model egem and to compare its performance with the value of simple topographical and morphological indices in the prediction of ephemeral gully erosion analysis shows that egem is not capable of predicting ephemeral gully cross sections well although conditions for input parameter assessment were ideal some parameters such as channel erodibility critical flow shear stress and local rainfall depth showed great uncertainty rather than revealing egem s inability of predicting ephemeral gully erosion this analysis stresses the problematic nature of physically based models since they often require input parameters that are not available or can hardly be obtained with respect to the value of simple topographical and morphological indices in predicting ephemeral gully erosion this study shows that for winter gullies and summer gullies respectively over 80 and about 75 of the variation in ephemeral gully volume can be explained when ephemeral gully length is known moreover when previously collected data for ephemeral gullies in two mediterranean study areas and the data for summer gullies formed in the belgian loess belt are pooled it appears that one single length l volume v relation exists v 0 048 l 1 29 r 2 0 91 these findings imply that predicting ephemeral gully length is a valuable alternative for the prediction of ephemeral gully volume a simple procedure to predict ephemeral gully length based on topographical thresholds is presented here secondly the empirical length volume relation can also be used to convert ephemeral gully length data extracted from aerial photos into ephemeral gully volumes

appalachian cold air damming abstract appalachian cold air damming is investigated by means of 1 a 50 yr monthly climatology 2 a synoptic case study of the event of 21 23 march 1985 and 3 an investigation of the flow structure and force balance within the cold dome the climatology reveals cold air damming is a year round phenomenon in the southern appalachians with the most frequent prolonged and intense events occurring in winter particularly december and march when three five events per month can be expected cold air damming is least frequent and intense in july the synoptic case study reveals that cold air damming is critically dependent upon the configuration of the synoptic scale flow the cold dome can be identified by a u shaped ridge trough in the sea level isobar thermal patterns and the 930 mb height temperature fields representative of conditions at the base of the inversion overlying the cold dome differential horizontal and vertical thermal advection as well as adiabatic and evaporative cooling are r

soil freeze thaw induced changes to a simulated rill potential impacts on soil erosion abstract flows in natural rills on hillslopes transport significantly more sediment down slope than overland flows which makes rills geomorphically significant landscape features the erosivity e g sediment transport capacity of the flows in rills is partially a function of the cross sectional geometry of the rill which determines flow velocity and depth conversely rill geometry is determined by flow erosivity and by soil processes that affect the erodibility and stability of soil along the rill thus complex feedbacks exist in the mechanics of rill erosion the objective of this study was to measure the effects of one of the soil processes that affect rill geometry soil freeze thaw ft cycling an unvegetated rectangular rill was subjected to two ft cycles each lasting several days in a controlled laboratory setting the ft cycling increased the water content and reduced the cohesion in the surface soil along the rill sufficiently to induce soil slumps and mud flows along the sidewalls of the rill these mass failures changed the rectangular rill to a triangular one which reduced the hydraulic radius of the rill by 32 using manning s equation it was estimated that this new geometry could reduce the velocity of the flow in this altered rill by about 25 the persistence of the new rill shape and thus that of the slower flow would depend on the complex interactions between flow velocity and the resistance of the slumped sediment to those flows that persistence was not investigated in this experiment these results can be used in parameterizing models of rill evolution that incorporate widening of rills by mass failures along the rill sidewalls

an improved method for shallow water flow velocity measurement with practical electrolyte inputs summary the measurement of shallow water flow velocity is of interest to hill slope hydrology and soil erosion mechanics lei et al lei t xia w zhao j 2005 method for measuring velocity of shallow water flow for soil erosion with an electrolyte tracer journal of hydrology 301 139 145 proposed an electrolyte pulse method for the purpose but found that the velocity measured at short distances from the salt injector was not as well estimated as those further away from the injector though it is desirable to estimate velocity at short distances for the purpose of portable device development in this study the system was improved over the previous development an additional sensor was added at the salt injection location to register the input signal as the actual boundary condition function instead of using the pulse assumption two function forms a normal distribution function normal model and a sine function sine model were suggested to approximate the measured boundary conditions these two determined boundary models were used to fit the experimentally obtained data using the least square method to determine the model parameters of the boundary conditions the determined normal model and the sine model were both used to solve the transport processes as the convolution integrals of the pulse response and the actually determined boundary functions so as to determine the shallow water flow velocity laboratory experiments were conducted to get data to verify the proposed methods and computational procedures the experiment device included a flume 4 m long and 15 cm wide a solute injector a data logger for control and data acquisition and a computer with specially designed software for data measurement and velocity estimation the experiments involved three flow rates 12 24 and 48 l min 1 and three slope gradients 4 8 and 12 six sensors were used to measure the solute transport processes at 5 30 60 90 120 and 150 cm from the location where the salt solute was injected into the water flow the solutions of both the normal model and sine model fitted the measured data very well for all the experimental conditions the velocities at different distances from the salt solution injector and under different flow rates and slope gradients as computed by the two models were almost identical which indicated the feasibility of the method and the computational procedures as well as the two suggested models for velocity estimation the velocity values estimated by the normal and sine models agreed also with those measured by using the floating objects and the volumetric method these demonstrated the rationality of the improved methods for shallow water flow velocity measurement the results will be useful to design a practical system for the measurement of shallow water flow velocity

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

analysis of water level response to rainfall and implications for recharge pathways in the chalk aquifer se england summary water table response to rainfall was investigated at six sites in the upper middle and lower chalk of southern england daily time series of rainfall and borehole water level were cross correlated to investigate seasonal variations in groundwater level response times based on periods of 3 month duration the time lags in days yielding significant correlations were compared with the average unsaturated zone thickness during each 3 month period in general for cases when the unsaturated zone was greater than 18 m thick the time lag for a significant water level response increased rapidly once the depth to the water table exceeded a critical value which varied from site to site for shallower water tables a linear relationship between the depth to the water table and the water level response time was evident the observed variations in response time can only be partially accounted for using a diffusive model for propagation through the unsaturated matrix suggesting that some fissure flow was occurring the majority of rapid responses were observed during the winter spring recharge period when the unsaturated zone is thinnest and the unsaturated zone moisture content is highest and were more likely to occur when the rainfall intensity exceeded 5 mm day at some sites a very rapid response within 24 h of rainfall was observed in addition to the longer term responses even when the unsaturated zone was up to 64 m thick this response was generally associated with the autumn period the results of the cross correlation analysis provide statistical support for the presence of fissure flow and for the contribution of multiple pathways through the unsaturated zone to groundwater recharge

a frequency domain approach to groundwater recharge estimation in karst this paper presents an alternative method for determining the values of parameters of a groundwater recharge model the phreatic zone of a karst aquifer is considered as the linear and time invariant filter that transforms the input signal of groundwater recharge rates into the output signal of spring discharges similarities between transfer functions of total rainfall rates and transfer functions of groundwater recharge rates are the basis for developing the parametric periodogram depending on parameters of a groundwater recharge model the values of parameters are estimated by minimizing the differences between the parametric periodogram and a periodogram of spring discharges the approximate whittle log likelihood function is the criterion for determining the optimal values of the parameters by using this frequency domain approach groundwater balance calculations are avoided so the method can be applied on unexplored karst aquifers when groundwater balance cannot be achieved without extensive geologic and hydrogeologic investigations the results of the applications on two springs located in the dinaric karst area in croatia are discussed

hydraulics and erosion in eroding rills rills often act as sediment sources and the dominant sediment and water transport mechanism for hillslopes six experiments were conducted on two soils and a uniform sand using three experimental methodologies the results of this study challenge the assumption often used in hydrologic and erosion models that relationships derived for sheet flow or larger channel flow are applicable to actively eroding rills velocity did not vary with slope and reynolds number was not a consistent predictor of hydraulic friction this result was due to interactions of slope gradient flow rate erosion and the formation of rill roughness bed structures and head cuts a relationship for rill flow velocities was proposed stream power was found to be a consistent and appropriate predictor for unit sediment load for the entire data set while other hydraulic variables were not the data for stream power and sediment load fit the form of a logistic curve r2 0 93 which is promising relative to recently proposed erosion models which are based on probabilistic particle threshold theory

influence of terrain resolution on banded convection in the lee of the rocky mountains abstracton 16 17 february 2007 snowbands formed in the lee of the rocky mountains in wyoming colorado and nebraska on the anticyclonic shear side of a midlevel jet streak two types of bands were prevalent a longer wider band associated with frontogenesis along an equatorward moving cold front major band and multiple shorter narrower bands farther poleward minor bands to understand how the upstream terrain affected the occurrence and intensity of the bands multiple mesoscale model simulations were performed in which the terrain was incrementally smoothed the evolutions of the synoptic patterns were similar in all simulations that included topography but the synoptic pattern differed and no bands developed in a simulation with a flat land surface these results allowed a focus on the changes to the banded precipitation due to the terrain resolution remarkably although the exact location of the bands differed from run to run the bands in all simulations with topography were in roughly the s

rill erosion in natural and disturbed forests 1 measurements 1 rill erosion can be a large portion of the total erosion in disturbed forests but measurements of the runoff and erosion at the rill scale are uncommon simulated rill erosion experiments were conducted in two forested areas in the northwestern united states on slopes ranging from 18 to 79 we compared runoff rates runoff velocities and sediment flux rates from natural undisturbed forests and in forests either burned at low soil burn severity 10 months or 2 weeks post fire high soil burn severity or subject to skidding of felled logs the runoff rates and velocities in the natural sites 2 7 l min 1 and 0 016 m s 1 respectively were lower than those in all the disturbed sites 12 to 21 l min 1 and 0 19 to 0 31 m s 1 respectively except for the 10 month old low soil burn severity site where the velocity 0 073 m s 1 was indistinguishable from the natural sites the mean sediment flux rate in the natural sites also was very small 1 3 10 5 kg s 1 as compared to the rates in the disturbed areas 2 5 10 4 to 0 011 kg s 1 the hillslope gradient did not affect the runoff or sediment responses the sediment flux rates generally were greater in the initial stage of each inflow period than in the steady state condition but there was no corresponding transient effect in runoff rates rill erosion modeling implications based on these data are presented in part 2 of this study

estimating rill erosion process from eroded morphology in flume experiments by volume replacement method abstract rills are commonly found on the sloped farm fields in the loess regions worldwide especially on chinese loess plateau the erosion process along a rill provides information for understanding the rill erosion mechanism this study uses a volume replacement method to estimate the rill erosion processes by refilling the eroded rill segments the sediment concentration was calculated by summering the eroded soil mass and divided by the total water volume during the erosion period a flume that was 0 6 wide and 12 m long was subdivided into strips of 0 1 m wide and 12 m long to imitate eroding rills a typical silty loam soil from the loess plateau of china was used for the experiments the commutative eroded rill volumes along the rills under five slopes and three flow rates were measured at 11 rill segments all the sediment laden runoff was harvested at the rill outlet to measure the average sediment concentration the sediment concentrations at locations higher than that at the outlet were caused by sediment deposition and removed from the data set the computed sediment concentration processes increased with slope gradient and flow rate they also increase with rill length exponentially with all the coefficients of determination above 0 95 the results were about the same of the previous studies with sampling method this demonstrates that the proposed method is a feasible approach to estimate rill erosion distribution the data set is applicable to the estimation of rill erosion model parameters this study will provide a basis for estimating rill erosion model parameters

suitability of transport equations in modelling soil erosion for a small loess plateau catchment erosion models have not often been applied to very steep terrain such as the gully catchments of the chinese loess plateau the purpose of this research was to evaluate the suitability of a number of transport equations for use in erosion modelling under loess plateau conditions to do this the equations were programmed into the lisem model which was applied to the 3 5 km2 danangou catchment in the rolling hills region of the loess plateau previous evaluations of transport equations used either flume tests or river sections and did no spatial modelling the results show that some equations predicted physically impossible concentrations defined as above 1060 g l the results were evaluated by using two methods 1 by comparing predicted and measured sedigraphs and sediment yield at the catchment outlet and 2 by comparing the fraction of the catchment in which physically impossible transport capacities occurred the results indicated that for the small grain sizes high density flows and steep slopes of the gully catchments on the loess plateau the shields parameter attained very high values furthermore the transport threshold can usually be neglected in the equations most of the resulting equations were too sensitive to slope angle abrahams schoklitsch yalin bagnold low and rickenmann so that transport rates were overpredicted for steep slopes and underpredicted for gentle slopes the yang equation appeared to be too sensitive to grainsize the govers equation performed best mainly because of its low slope dependency and is therefore recommended for erosion models that simulate sediment transport by flowing water in conditions with small grain sizes and steep slopes

quantifying the place of karst aquifers in the groundwater to surface water continuum a time series analysis study of storm behavior in pennsylvania water resources summary though karst aquifers have commonly been identified with respect to their behavior as intermediate between ground and surface water their putative location between these end members is generally descriptive rather than quantitative autocorrelation and spectral analysis of data from four karst springs three wells and eight stream gauges in pennsylvania illustrate that specific karst water resources exhibit widely varying inertia with lag times that overlap those of groundwater and surface water when analyzed in the frequency domain the same data reveal distinctive patterns for each type of water resource the four springs display characteristic lag times ranging from 5 to 25 days compared to 1 10 days for streams and 11 46 days for wells physically karst waters may behave as a mix of porous media fracture and open channel flow but in temporal terms the balance of this mix results in a range of system behaviors with characteristic periodicities evident in the karst aquifers in the frequency domain karst aquifers manifested slow flow paths as a gradual fall off at lower frequency and quick flow paths as a flattening at high frequency our comparison of water resources across different time periods revealed that the period considered can have strong effects on results one spring displayed characteristic lag times of 12 and 25 days for two different time spans to directly compare water resources over relatively short time scales precipitation inputs must be similar and data sets must cover the same period otherwise substantial differences in lag times can be due to data collection and input differences rather than system characteristics this limitation is less when the same data are analyzed in the frequency domain

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

relationship between discharge velocity and flow area for rills eroding loose non layered materials a relationship between discharge flow velocity and flow area in rills is established using data from four field and laboratory studies the proposed relationship is shown to predict successfully flow velocities measured in six other studies although slopes range from 0 035 to 0 45 and soil materials range from stony sands over silt loams to vertisols mean flow velocity can be well predicted from discharge alone thus there is no important influence of slope and or soil material characteristics on flow velocities in rills the proposed relationship may be used to improve performance of deterministic flow routing models when applied to rilled catchments furthermore it allows the calculation of unit stream power which has been shown to be related to the transporting capacity of overland flow in terms of slope and discharge

rill erosion and morphological evolution a simulation model a mathematical model is advanced to simulate dynamically and spatially varied shallow water flow and soil detachment transport and deposition in rills the model mimics the dynamic process of rill evolution including variable rates of sediment redistribution along the bed and changes in local bed morphology the sediment source term in the model uses a point scale probabilistic relationship based on turbulent flow mechanics and a recently developed sediment transport relationship for rills based on stream power the interdependent feedback loops between channel bed morphology local flow hydraulics and local scour and deposition within the framework of the full hydrodynamic equations with inertial terms constitute a mathematical model with the capacity to represent spatial variability and temporal evolution of the rill finite elements were applied to numerically solve the hydrodynamic and sediment continuity equations a series of laboratory flume experiments were performed to evaluate the model initial bed slopes were 3 5 and 7 with step increases of water inflow rates of 7 6 11 4 and 15 2 l min 1 the soil material used in the flume was a kaolinitic sandy clay loam the rill model equations were solved for increasingly complex cases of spatial and temporal variabilities the model followed measured patterns of morphological changes as the rill evolved which suggests that the feedback loops in the model between erosion bed morphological changes and hydraulics were adequate to capture the essence of rill evolution

laboratory investigations of rill dynamics on soils of the loess plateau of china abstract we conducted a laboratory study on rill network evolution with detailed measurements under controlled experimental conditions the concepts of fractal geometry entropy and topology were used to quantify rill erosion intensity and morphology the objectives of this study are to reveal rill erosion processes and rill network development under different rainfall intensities and to present some indicators to provide a quantitative description of rill morphology a soil pan 5 m long 1 m wide and 0 6 m deep with slope gradient of 20 was subjected to three successive rainfall events under rainfall intensities of 66 94 and 127 mm h 1 the results showed that rainfall intensity played a major role in rill erosion the development of a rill network is most rapid under medium intensity rainfall rainfall intensity that is too weak or too strong is not conducive to rill development as rainfall duration increased under the same rainfall intensity the values of soil loss rill density geomorphologic comentropy and nodes increased rill network development was slow at the early stage but became more rapid at a later stage the results also indicated that the geomorphologic comentropy was the best basic morphological indicator of rill erosion and the number of rill nodes was the best derived morphological indicator of rill morphology which was followed in descending order by the fractal dimension rill density and bifurcation ratio

the contribution of time series analysis to the study of the hydrodynamic characteristics of the karst systems application on two typical karst aquifers of greece trifilia almyros crete time series analysis was applied to the precipitation spring discharge and piezometric head data of two representative karst systems of greece in order to study the function hydrodynamic behaviour and hydraulic properties of the aquifers results obtained through autocorrelation spectral density cross correlation cross amplitude gain coherence and phase functions showed that the trifilia karst system is slightly karstified and has a large storage capacity baseflow dominates while quickflow is absent due to the lack of a well organized karst network suggesting that probably darcian conditions exist on the other hand unlike the trifilia karst system the karstification processes in the almyros karst system are more enhanced producing a better developed karst network but contrary to the typical karst systems baseflow and quickflow coexist this system can be classified as an intermediate case between the two extreme karst types

sediment transport in rill flow under deposition and detachment conditions the understanding of soil erosion processes and the development of accurate erosion prediction models require understanding of detachment deposition and sediment transport in rills the objectives of this study were to determine whether sediment transport capacity is a unique value for given soil flow rate and slope and to determine if equilibrium sediment concentration in the rill obtained by detachment was different from that observed under depositional conditions experiments on a carmi loam fine mixed mesic typic hapludalf simulated rill erosion under net detachment and net deposition conditions two discharge rates of 6 and 9 l min 1 and two sediment input regimes of 0 and excess of transport capacity were tested on soil beds with lengths of 2 4 6 7 and 8 m at 7 slope sediment load reached steady state conditions within the 8 m distance on the rill at 9 l min 1 discharge 8 m length and excess sediment added to the flow sediment delivery was 71 g l 1 versus 31 g l 1 for the corresponding case with no sediment added overall for the conditions tested rill flow transported two times more sediment than it could detach the flow did not reach its maximum potential transported load through detachment of soil due in part to changes in the sediment size distribution under deposition and possibly to the protective action of bedload particles moving along the rill bottom and or changes in flow turbulence associated with sediment laden flow d 2003 elsevier science b v all rights reserved

effects of rock fragment covers on erosion and transport of noncohesive sediment by shallow overland flow rock fragments on soil surfaces can have a variety of contrasting effects on the hydraulics of overland flow and soil erosion this makes modeling soil erosion difficult systematic studies are needed to assess the effects of rock fragments on the hydraulics of overland flow and to specifically relate these hydraulics to sediment yield therefore flume experiments were conducted in which overland flow was applied to a highly erodible sediment surface covered by various percentages of rock fragments high local turbulence was caused by horseshoe vortex erosion around individual rock fragments for a given discharge and slope the dimension of the scour was affected by the space between the rock fragments for low cover percentages the scour can develop undisturbed and sediment yield increases with percent of rock fragment cover up to about 20 sediment yield then declines as percent cover increases above 20 beyond a cover threshold value of 20 the larger opportunity for scour hole development is counteracted by limited inter rock fragment space that does not allow scour holes to develop to their full extent as sediment yield varies nonmonotonically with rock fragment cover percent sediment yield cannot be predicted by spatially averaged flow hydraulics

flume experimental evaluation of the effect of rill flow path tortuosity on rill roughness based on the manning strickler equation abstract numerous soil erosion models compute concentrated flow hydraulics based on the manning strickler equation v kst r2 3 i1 2 even though the range of the application on rill flow is unclear unconfined rill morphologies generate local friction effects and consequently spatially variable rill roughness which is in conflict with the assumptions of sectional uniform channel flow and constant channel roughness of the manning strickler equation the objective of this study is to evaluate the effect of rill morphology on roughness and hence to assess the manning strickler roughness coefficient kst by rill morphological data a laboratory experiment was set up to analyse rill hydraulics and roughness of i free developed rill fdr flows and ii straight constrained rill scr flows in the flume the flume experiment generated manning strickler roughness coefficients kst between 22 m1 3 s 1 and 44 m1 3 s 1 reflecting a potential area of the roughness parameter uncertainty it was found that fdr experiments generated significantly lower kst values compared to scr experiments because skin and local friction effects in the fdr experiments were more efficient reducing flow velocity probably due to higher energy dissipation rill flow path tortuosity tort was used to describe the rill morphology of the experiments and correlation statistics between tort and kst identified considerable explanatory capacity of rill flow path tortuosity on rill roughness the flume study demonstrated that a regression model between tort and kst can be used to assess local friction effects of unconfined rill morphologies and hence to reduce the area of uncertainty of the manning strickler roughness parameter

time series and stochastic analyses to study the hydrodynamic characteristics of karstic aquifers the regional study of hydrodynamic characteristics of karstic aquifers is challenging because of the great variety of lithology and the structural complexity found in carbonate formations in order to improve this situation a combined approach of time series and stochastic analyses was adopted to assess the hydrodynamic behaviour of the karstic aquifers to achieve this daily flow rates of 20 springs were taken from the 11 most significant aquifer units of the basque country the results demonstrate the presence of memory effects which modulated the input rainfall for short medium and long term storage capacity resulting in hydrodynamic properties such as system memory response time and mean delay between input and output they reflect the storage and the manner in which these are filled and emptied thus indicating the karstification of the aquifer likewise the hydrodynamic and hydraulic classification obtained from the stochastic analysis provides a complementary approach to characterize the hydraulic behaviour of the studied karstic aquifers the discussed examples indicate that this approach provides an excellent method to research hydrological karst systems it is also shown that the use of hydrologic time series alone does not lead to a satisfactory classification of the hydrodynamic characteristics therefore the general approach to hydrological regionalization in karst areas should take into account the structural complexity heterogeneity of the lithology and the degree of karstification only in this case will the regionalization be physically founded leading to a regional understanding of the hydrodynamic characteristics and flow conditions in a karst aquifer copyright 2009 john wiley sons ltd

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

application of spectral analysis of daily water level and spring discharge hydrographs data for comparing physical characteristics of karstic aquifers abstract bivariate time series techniques in spectral domain of daily rainfall and water level of piezometers or discharge of springs in karstic aquifers are employed to evaluate the lag times delay of aquifers response to rainfall events the evaluation results show that the physical characteristics of karstic aquifers can be compared with each other by using the outcomes of these analyses with attention to dual porosity idea of karstic aquifers two lag times t 1 t 2 can be computed which are related to flow of water through larger fractures conduit flow and matrix of the rock diffuse flow respectively results obtained from these functions correspond to the findings of physical characteristics compiled from field investigations comparable to dual porosity idea in regard to recharge through the larger fractures in the first step and finer porosity of the rock in the second step the idea of dual recharge in karstic aquifers is presented application of these techniques is verified using daily rainfall and water level of qara sabzpooshan and kaftarak piezometers and daily discharge of qasreqhomsheh karst spring in maharlu basin in iran 52 20 52 40 e and 29 20 29 40 n having different degree of karstification in their surroundings