holocene climatic changes and vegetation development in the kuril islands abstract the response of kuril island vegetation to climatic changes during the holocene is reconstructed from data obtained from key sections that included various depositional environments these climatic fluctuations were not as marked in the kuril archipelago as they were in nearby continental margins and large islands during the early holocene dwarf stone pine coniferous and birch forest prevailed in the south kurils and tundra landscapes in the north kurils the greatest northward movement of kuril vegetation zones occurred during the holocene optimum 6600 5000 14c bp mean annual temperatures in the kuril islands were 2 3 c higher than modern shifts in the location of warm and cold marine currents which strengthened or dampened insolation driven climatic changes played an important role in vegetation development cool temperate broadleaf forests and mixed coniferous broadleaf forests were widespread on south kurils rising holocene sea levels flooded land bridge connections to hokkaido island and the mainland resulting in the formation of several small islands in the south kurils meadows and boggy landscapes prevailed this flooding had a great effect on repopulation of island biota as did the deep straits that separate southern islands from the central and north kurils all paleovegetation associations can be found on the current landscape although their geographic distribution has changed during the holocene no introduction of plants from adjacent land occurred in the holocene forb and graminoid meadows characterized the middle holocene vegetation of central kurils on north kurils forb meadows were widespread tundra area decreased climatic changes did not occur synchronously throughout the kurils at times not even on the closest islands local volcanism played a special role in kuril vegetation history the considerable microclimatic variability within the islands also has been important in determining the development and preservation of vegetation communities and their reaction to more regional climatic changes

digital elevation model resolution effects on terrain attribute calculation and quantitative soil landscape modeling the accuracy of digital elevation models dem and dem derived products depends on several factors including the horizontal resolution and vertical precision at which the elevation data are represented and the source of the elevation data this accuracy becomes increasingly important as we extend the use of dem data for spatial prediction of soil attributes our objective was to compare terrain attributes and quantitative soil landscape models derived from grid based dem represented at different horizontal resolutions 10 and 30 m represented at different vertical precisions 0 1 and 1 m and acquired from different sources decreasing the horizontal resolution of the field survey dem produced lower slope gradients on steeper slopes steeper slope gradients on flatter slopes narrower ranges in curvatures larger specific catchment areas in upper landscape positions and lower specific catchment areas values in lower landscape positions overall certain landscape features were less discernible on the 30 m dem than on the 10 m dem decreased vertical precision produced a large proportion of points with zero slope gradient and zero slope curvature and a large number of steeply sloping and more highly curved areas differences among dem from different sources were more significant with less accurate representation of depressions and drainage pathways with the usgs dem as compared to the field survey dem empirical models developed from different dem included similar predictive terrain attributes and were equally successful in predicting a horizon depth ahd in the validation data set

a physical explanation of the cumulative area distribution curve a physical explanation for the behavior of the cumulative area distribution cad based on the tokunaga channel network model is given the cad is divided into three regions the first region for small areas is dependent on hillslope flow accumulation patterns and represents the catchment average of the hillslope flow accumulation in the diffusive erosion dominated areas upstream reaches of the catchment the second region represents that portion of the catchment dominated by fluvial erosion this region is well described by a log log linear power law which results from the scaling properties of the channel network the scale exponent b is highly sensitive to a parameter of the tokunaga stream numbering scheme the exponentb converges to 0 5 for higher order tokunaga networks for parameters consistent with topological random networks small networks have lower values ofb which asymptotic converges tob 0 5 as the catchment scale increase the third region reflects the lowest reaches of the channel network the scale of the catchment and is a boundary effect an explicit analytical solution to the scaling properties in the second region is derived on the basis of the tokunaga network model the cumulative distribution of drainage area is the percent age of the catchment that has an area per unit width draining through a point which is greater than or equal to a given area it is a geomorphologic measure that characterizes part of the catchment hydrology and is a measure commonly used by geo morphologists and hydrologists to characterize the scale invari ant structure of channel networks tarboton et al 1989 ro driguez iturbe et al 1992 inaoka and takayasu 1993 la barbera and roth 1994 this cumulative area distribution cad characterizes the scaling properties of drainage area the cad and its scaling properties are key components in the development of physically based models that link geomorphol ogy and hydrology perera 1997 ibbitt et al 1997 perera 1997 showed that slope of the cad in both the hillslope and channel domains is important for describing the geomorphic impact on subsurface saturation excess runoff generation using a digital elevation model dem of a catchment the drainage path through and the drainage area per unit width of each point in the catchment can be computed for a grided dem the cumulative area a is determined as the number of pixels within the catchment which have drainage area a num ber of pixels draining through greater than or equal to some specified drainage area a

an efficient and comprehensive method for drainage network extraction from dem with billions of pixels using a size balanced binary search tree abstract with the increasing resolution of digital elevation models dems computational efficiency problems have been encountered when extracting the drainage network of a large river basin at billion pixel scales the efficiency of the most time consuming depression filling pretreatment has been improved by using the o n log n complexity least cost path search method but the complete extraction steps following this method have not been proposed and tested in this paper an improved o n log n algorithm was proposed by introducing a size balanced binary search tree bst to improve the efficiency of the depression filling pretreatment further the following extraction steps including the flow direction determination and the upslope area accumulation were also redesigned to benefit from this improvement therefore an efficient and comprehensive method was developed the method was tested to extract drainage networks of 31 river basins with areas greater than 500 000 km 2 from the 30 m resolution aster gdem and two sub basins with areas of approximately 1000 km 2 from the 1 m resolution airborne lidar dem complete drainage networks with both vector features and topographic parameters were obtained with time consumptions in o n log n complexity the results indicate that the developed method can be used to extract entire drainage networks from dems with billions of pixels with high efficiency

invariance and scaling properties in the distributions of contributing area and energy in drainage basins a the cumulative probability distributions for stream order stream length contributing area and energy dissipation per unit length of channel are derived for an ordered drainage system from horton s laws of network composition it is shown how these distributions can be related to the fractal nature of single rivers and river networks finally it is shown that the structure proposed here for these probability distributions is able to fit the observed frequency distri butions and their deviations from straight lines in a log log plot

calibrating fluvial erosion laws and quantifying river response to faulting in sardinia italy abstract it is now widely accepted that rivers modify their erosion rates in response to variable rock uplift rates resulting in changes in channel slope that propagate upstream through time therefore present day river morphology may contain a record of tectonic history the simple stream power incision model can in principle be used to quantify past uplift rates over a variety of spatial and temporal scales nonetheless the erosional model s exponents of area and slope m and n respectively and bedrock erodibility k remain poorly constrained in this paper we will use a geologically and geomorphically well constrained plio pleistocene volcanic landscape in central sardinia italy to calibrate the stream power erosion equation and to investigate the slip rate of faults that have been seismically quiescent in the historic past by analysing digital elevation models geological maps and landsat imagery we have identified the geomorphic expression of several volcanic features eruption centres and basaltic lava flows and three normal faults with 6 to 8 km fault traces within the outcrop downstream river longitudinal profiles show a similar transient response to relative base level fall probably as a result of relief inversion at the edge of the volcanic outcrop from measurements of incision local slope and upstream catchment area across eight different rivers we calculate n 1 m 0 50 0 02 and using a landscape age from literature of 2 7 ma bedrock erodibility k 0 10 0 04 m 1 2m myr 1 there are also knickpoints on rivers upstream of two normal faults and we used numerical inverse modelling of the longitudinal profiles to predict the slip rate of these faults since 2 7 ma the results from the inverse model show that the erosional parameter values derived in this study can produce theoretical longitudinal profiles that closely resemble observed river profiles upstream of the faults the lowest misfit theoretical longitudinal profiles were generated by a model of temporally discontinuous footwall uplift with consistently low throw rates

on the prediction of channel heads in a complex alpine terrain using gridded elevation data 1 threshold conditions for channel initiation are evaluated by using gridded elevation data derived from a lidar survey a reliable algorithm for the determination of surface flow paths and field observations of channel heads for a study area located in the eastern italian alps these threshold conditions are determined by considering the channel heads observed across a portion of the study area and computing the related values of 1 drainage area a 2 area slope function as2 with s being the local slope and 3 strahler order of surface flow paths extracted from gridded elevation data attention is focused on the dependence of the obtained threshold values on the size of grid cells involved and on the ability of the identified threshold conditions to provide reliable predictions of channel heads across the entire study area the results indicate that the threshold values of a as2 and are all significantly dependent on grid cell size and the uncertainty in the determination of threshold values of is significantly smaller than that affecting the determination of threshold values of a and as2 the comparison between predicted and observed channel heads indicates that the considered methods display variable reliability and sensitivity over different drainage basins and grid cell sizes with a general tendency to predict more channel heads than can be observed in the field acceptable predictions are normally obtained where channel heads are formed essentially by surface runoff more comprehensive methods seem however to be needed to predict channel heads affected by groundwater seeping upward

prediction of concentrated flow width in ephemeral gully channels empirical prediction equations of the form w d aq b have been reported for rills and rivers but not for ephemeral gullies in this study six experimental data sets are used to establish a relationship between channel width w m and flow discharge q m 3 s 1 for ephemeral gullies formed on cropland the resulting regression equation w d 2 51 q 0 412 r 2 d 0 72 n d 67 predicts observed channel width reasonably well owing to logistic limitations related to the respective experimental set ups only relatively small runoff discharges i e q 0 02 m 3 s 1 were covered using field data where measured ephemeral gully channel width was attributed to a calculated peak runoff discharge on sealed cropland the application field of the regression equation was extended towards larger discharges i e 5 10 4 m 3 s 1 q 0 1m 3 s 1 comparing w q relationships for concentrated flow channels revealed that the discharge exponent b varies from 0 3 for rills over 0 4 for gullies to 0 5 for rivers this shift in b may be the result of i differences in flow shear stress distribution over the wetted perimeter between rills gullies and rivers ii a decrease in probability of a channel formed in soil material with uniform erosion resistance from rills over gullies to rivers and iii a decrease in average surface slope from rills over gullies to rivers the proposed w q equation for ephemeral gullies is valid for sealed cropland with no significant change in erosion resistance with depth two examples illustrate limitations of the w q approach in a first example vertical erosion is hindered by a frozen subsoil the second example relates to a typical summer situation where the soil moisture profile of an agricultural field makes the top 0 02 m five times more erodible than the underlying soil material for both cases observed w values are larger than those predicted by the established channel width equation for concentrated flow on cropland for the frozen soils the equation w d 3 17 q 0 368 r 2 d 0 78 n d 617 was established but for the summer soils no equation could be established copyright 2002 john wiley sons ltd

catchment scale analysis of the effect of topography tillage direction and unpaved roads on ephemeral gully incision high resolution airphotographs and digital elevation models dems were used to study areas prone to gully incision in a small agricultural catchment in northern israel data are analyzed to understand better the integrated effect of environmental and human factors on gully incision the effect of flow accumulation slope unpaved roads density and tillage direction on gully width and length is found discontinuous and topography in the form of the topographic threshold was found to be the most dominant factor on gully incision in the catchment scale the topographic threshold coefficients observed in yehezkel catchment were lower than those found in previous studies due to the effect of large rainfall events during the early winter season when the soil in fields is still unprotected by crops in addition a survey of previous studies shows that in cultivated areas there is relationship between the topographic threshold coefficients a multiplier and b exponent the influence of unpaved roads and tillage direction on gully incision was also found significant and consistent during the two seasons observed while the non parametric test showed that it added to the prediction in 15 of the gullies incision points density plot show that of the two parameters the unpaved roads were found to have greater influence on gully head location than tillage direction studying the phenomenon on the catchment scale allows better understanding of the effect of spatial variation on gully head location copyright 2009 john wiley sons ltd

pollen and radiolarian records from deep sea core rc14 103 climatic reconstructions of northeast japan and northwest pacific for the last 90 000 years using modern pollen and radiolarian distributions in sediments from the northwest pacific and seas adjacent to japan to interpret floral and faunal changes in core rc14 103 44 02 n 152 56 e we recognize two major responses of the biota of eastern hokkaido and the northwest pacific to climatic changes since the last interglaciation relatively stable glacial environments 80 000 20 000 yr b p were basically cold and wet 8 c and 1200 mm mean annual temperature and precipitation respectively supporting climax broadleaf deciduous forest with quercus and ulmus zelkova with surface waters in the northwest pacific characterized by warm 1 5 c winter and cold 10 4 14 3 c summer temperatures climatic evidence from rc14 103 shows a high degree of local and regional variation within the context of global climatic change correlative ocean and land records provide the detailed input necessary to assess local regional responses to variations in other key elements i e solar radiation monsoonal variations of the northeast asian climate system

late quaternary atmospheric and oceanographic variations in the western pacific inferred from pollen and radiolarian analyses abstract pollen and radiolarian analyses of sediment from four piston cores located along a south north transect 28 44 n off the east coast of japan yield detailed records of variations in terrestrial and marine climate of this region for the last 140 ka the last interglacial climate of the southern half of japan was characterized by increased temperature and precipitation at least across central japan compared with today off southern japan surface were cooler during summer than at present off central japan both summer and winter sea surface temperatures were cooler than today early glacial 115 71 ka bp climate across central and southern japan alternated between wet and dry warm temperate with surface waters offshore warmer in summer and winter than during the penultimate interglacial temperatures and precipitation in japan reached low levels early during the full glacial phase and remained relatively low throughout much of the full glacial 71 14 ka bp cold sea surface temperatures at all our sites coincided with these cold conditions on land temperatures across much of japan began to increase steadily during the deglacial with surface waters offshore remaining at or near their glacial lows holocene vegetation patterns which continued to reflect an increase in temperature reached a maximum during early to mid holocene surface waters offshore however remained relatively cool during the early holocene with temperature maxima at most western pacific sites occurring in mid to late holocene we propose specific changes in the seasonal positions of atmospheric pressure cells to explain these climate variations that have occurred across the northeast asian northwest pacific region through the most recent interglacial glacial cycle results of this exercise show that there are no major discrepancies between climate reconstructions for mainland japan inferred from pollen and those for the western pacific derived from radiolarians

late holocene history of tokotan lake kuril archipelago russian far east the use of lacustrine records for paleoclimatic reconstructions from geologically dynamic settings abstract a high resolution multiproxy analysis of a core from tokotan lake urup island illustrates the complex paleoenvironmental signals that can be preserved in sedimentary deposits from geologically active areas such as the kuril archipelago diatom and geochemical analyses of the tokotan core suggest a shallowing and lessening of the lake area over the last 3450 cal bp without other proxies the record could be interpreted as showing a general decrease in precipitation over the late holocene however palynological data indicate no change in vegetation thereby implying no significant climatic variation neither of these paleoclimatic interpretations agrees with late holocene reconstructions from the kuril archipelago or the russian mainland paleomagnetic data imply variable sediment sources during the lake s history indicating alterations within the tokotan catchment e g shifts in gradients or sediment loads in the inflowing streams such changes would be particularly important in the shabalina river which today has formed a partial dam across the lake s outlet the results of the tokotan study indicate that other factors e g volcanism seismic activity sea level changes rather than climate were more probable determinants of the late holocene lake record given the geologic dynamism of the region it is perhaps not surprising that paleo records from the kuril islands display an inconsistency in the numbers and or duration of proposed holocene climatic oscillations underscoring the importance of multiproxy investigations in areas that are or have been geologically dynamic

holocene environments of central iturup island southern kuril archipelago russian far east two lake records document holocene changes in sea level vegetation and climate on the okhotsk and pacific sides of central iturup island southern kuril islands the sediment cores originated within tidal flats that subsequently developed into a marine strait which crosscut the island as sea levels rose during the early holocene brackish lagoons and eventually freshwater lakes formed by 7100 cal yr bp associated with warmer than present conditions past vegetation changes indicate a clear holocene thermal maximum recorded on the pacific coast but a less distinct optimum on the western shores 7200 6100 cal yr bp a gradual cooling toward modern levels occurred 6100 3500 cal yr bp four prominent layers of coarse sediment found in mid to late holocene lake deposits may correspond to intervals of climate cooling dune formation previously documented in coastal sections although chronological limitations question the synchronicity of these events across the south russian far east it seems probable that they have a regional signature however the mechanisms responsible for holocene climatic changes are likely the result of complex interactions of hemispheric scale atmospheric patterns marine characteristics and regional feedbacks rather than simply fluctuations in sea levels as suggested in the current interpretative model

submarine canyons in the bathtub abstract submarine megafans and their associated canyons have long attracted the attention of a large community in the earth sciences because they record the history of past erosional processes as such their morphology and sedimentary infill may be of use to unravel past climatic and tectonic evolution yet despite an important corpus of research on their structural characteristics we lack a well accepted quantitative description for the dynamics of the formation and growth of these sedimentary systems one of the main reasons for this lies in our inability to successfully understand reproduce and predict the dynamics of the channel systems tens to hundreds of meters deep several kilometers in width and hundreds of kilometers in length that build submarine fans here we report on a series of small scale laboratory experiments on the formation of subaqueous channels and lobes our experiments show that steady flow of a dense current on a bed of light particles can induce both spontaneous formation of channels longer than a few channel widths and spontaneous meandering

experiments on self channelized subaqueous fans emplaced by turbidity currents and dilute mudflows the passage of turbidity currents over submarine fans often results in intense channelization the channels are typically bounded by levees and they vary from mildly to strongly meandering the process of self channelization remains however somewhat obscure preliminary experiments reported here demonstrate for the first time that self channelization of subaqueous fans by turbidity currents can be reproduced at laboratory scale the same experiments also illustrate self channelization by dilute mudflows the resulting weakly sinuous channels can be predominantly depositional predominantly erosional or some combination of the two the channels can elongate to the length of the entire reach available for their formation they can show both gradual shift and avulsion a necessary condition for the formation of intricate channelization in the laboratory experiments appears to be a turbidity current that is insufficient to cover the entire area of the fan at any given time loose field analogs to the experimental channelized fans i e analogs that are imprecise but contain many similarities can often be found at the distal end of submarine fans two possible examples are cited one from the pochnoi system bering sea and one from the gulf of cadiz

digital terrain modelling a review of hydrological geomorphological and biological applications the topography of a catchment has a major impact on the hydrological geomorphological and biological processes active in the landscape the spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems furthermore topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology digital elevation models are the primary data used in the analysis of catchment topography we describe elevation data sources digital elevation model structures and the analysis of digital elevation data for hydrological geomorphological and biological applications some hydrologic models that make use of digital representations of topography are also considered

scale effects on the estimation of erosion thresholds through a distributed and physically based hydrological model abstract slope incision and subsequent development of rills gullies and channels are responsible for significant soil losses and are often irreversible with very high restoration costs particularly in semiarid environments the location of potential areas of erosion where these processes occur is vital to land management and conservation the study of the relationship between the local slope s and the drainage area a through the geomorphological relationship s a b combined with hydrologic simulation models has proved to be appropriate for the identification and characterisation of potential areas of incision especially when it takes into account the spatial distribution of soil properties and the evolution of hydrological processes however physical properties of soil digital elevation models dems and flow algorithms used may affect the results this study employs a distributed physically based hydrological model to evaluate the infiltration runoff relationships and their influence on selecting critical area from three dems with different resolutions the results show a significant scale effect on flow distribution and the location of threshold points on slopes the results obtained from a 30 m dem significantly differ from those obtained from 10 and 5 m dems because the former was unable to capture the spatial variability of geomorphic processes the selected set of critical points shows high s a correlations for different values of critical shear stress the physical model confirmed the dominance of surface runoff in the study site and was validated from field identification of erosion risk areas although for incision areas

power law distributions of discharge mass and energy in river basins river networks constitute dissipative systems with many spatial degrees of freedom previous work by mandelbrot 1983 and bak et al 1987 1988 1990 suggests that such systems will follow power law distributions in their mass and energy characteristics it is shown that this is the case for river networks where the exponent in the distribution p x x x is approximately equal to 0 45 and 0 90 for discharge and energy respectively in the case of several networks analyzed in north america when these variables are calculated for each individual link throughout the drainage network an explanation of the values of is offered based on the fractal structure of rivers and on principles of energy expenditure in river basins

middle and late holocene environments and vegetation history of kunashir island kurile islands northwestern pacific natural middle and late holocene environmental development of kunashiri island reflects global climatic changes and the migration of warm and cold currents dry and cool climate changed to warm and moist about 7000 6500 bp later than on hokkaido island at this time kuroshio current system became more active on kunashir island birch assemblages were replaced by cool temperate broadleaf forests in the south and mixed coniferous broadleaf forests in the north the highest sea level position reached 2 5 3 m above psl about 6500 6300 bp cooling about 4700 4500 bp island vegetation weakly changed that connected with warm current influence major regression at this period led to formation of extensive coastal dunefields the warming at the beginning of the late holocene was almost similar to the holocene optimum two minor transgressions are recorded about 4010 3400 and 2950 2620 bp active entrance of detrital material to the coastal zone resulted in growth of accumulative landforms vegetation changes and

the use of digital elevation models in the identification and characterization of catchments over different grid scales this study examines the ability of well known hydrological and geomorphological descriptors and statistics to differentiate between catchments with spatially varying geology size and shape subject to the same climate in the northern territory australia the effect of digital elevation model grid resolution on these statistics is also examined results demonstrate that catchment descriptors such as the area slope relationship cumulative area distribution and hypsometric curve can differentiate between catchments with different geology and resultant morphology but catchment network statistics are insensitive to differences in geology examination of the effects of digital elevation model grid scale demonstrates that while considerable catchment information can be gained at digital elevation grids greater than 10 m by 10 m hillslope and hydrological detail can be lost geomorphic descriptors such as the area slope relationship cumulative area distribution width function and strahler statistics were shown to be sensitive to digital elevation model grid scale but the hypsometric curve was not consequently caution is needed when deciding on an appropriate grid resolution as well as the interpretation and analysis of catchment properties at grid scales greater than that for optimal hillslope and area aggregation definition copyright 2005 john wiley sons ltd

shelf slope sedimentation during the late quaternary on the southwestern kuril forearc margin northern japan abstract we studied an active forearc margin off eastern hokkaido northern japan to identify the main influences on stratigraphic development from the last glacial to the present highstand this paper presents new data on the environment texture and sedimentation rates of forearc shelf slope sediments based on more than 300 samples of seafloor sediments and densely gridded sub bottom profiling records lowstand sedimentary wedges developed upon the shelf margins in areas with a large sediment supply and without incising canyons the transgressive and highstand deposits formed on the shelf in extensive low gradient and topographically low areas the narrow shelf is covered by sandy sediments where winnowed fines are likely to have escaped to the slope via gravity driven across shelf transport or ocean current induced along shelf transport the slope has a mid slope mud belt at water depths of 700 1600 m the sedimentation rates on the slope subsequent to 15 ka the late transgressive to highstand stage were just 10 70 of the rates prior to this period these changes in sedimentation rates are ascribed to spatially variable topography high sedimentation rates were maintained at topographically low and gently sloping areas even during highstand periods due to concentrations of nepheloid layers or deposition via sediment gravity flows on the other hand low sedimentation rates were recognized on topographic highs of interfluves on the upper slope or on axes of anticlines where main flows or overspills of turbidity currents decreased as sealevel rose these results suggest that sedimentologic and stratigraphic variations are tied to variations in the physical configuration of the shelf slope system being influenced by the local topography in addition to the climatic and oceanographic processes

climatic change at the end of the last glaciation in japan inferred from pollen in three cores from the northwest pacific ocean abstract late glacial pollen time series from high sedimentation rate marine cores kh79 3 c6 ch84 04 and ch84 14 show the rise of successional vegetation typified by betula during the replacement of boreal forest types picea and pinus by thermophilous quercus forests variations in these three marine pollen records replicate the trends and timing of pollen records from japan and the structure and timing of vegetation and climatic changes on the pacific coast of japan since the last glacial maximum in marine cores kh79 3 c6 ch84 04 and ch84 14 oxygen isotope and or marine faunal data have been interpreted as evidence of a cooling event in the northwest pacific ocean which is coeval with the younger dryas chronozone pollen records from these northwest pacific cores like those from japan do not exhibit a regionally replicated statistically robust pollen assemblage which can be unambiguously interpreted as evidence of a late glacial climatic reversal between ca 11 000 and 10 000 yr b p the apparent disparity between the terrestrial pollen and marine evidence for a climatic oscillation during the younger dryas chron in northeast asia further complicates the variable record of this brief late glacial event

paleoenvironments of kuril islands in late pleistocene holocene climatic changes and volcanic eruption effects the kuril islands are noted for a variety of landscapes from nemoral broadleaf forests to forest tundra and tundra some large islands display a distinct altitudinal zonality environments of the islands bear evidence of various catastrophic events that controlled the landscape evolution to a considerable extent changes of climate during the pleistocene were of particular importance in evolution of the environments dramatic rapid fluctuations of climate at the late pleistocene holocene boundary resulted in repeated restructuring of landscapes at the land bridge connecting the south kuriles and hokkaido in the southern part of the small kuril ridge open forests might persist until the land mass was broken into small islands dominated by meadow marsh vegetation since the middle holocene on the central and northern kuril islands environmental changes during the middle and late holocene resulted both from climatic fluctuations and from repeated fallout of volcanic ash deposition of organic matter began about 6 5 ka bp it resulted from the onset of more favorable conditions namely warming increase of moisture supply and reduction of volcanic activity the evolution of island landscapes consisted mainly in changes of relative area occupied by various plant communities most of which are present in modern vegetation the holocene climatic optimum was not particularly pronounced in this part of the great kuril ridge some consideration is given to issues of changes in zonal boundaries at different time intervals within late pleistocene and holocene

age source and distribution of holocene tephra in the southern kurile islands evaluation of holocene eruptive activities in the southern kurile arc abstract we identified 32 distinct layers of holocene tephra in the southern kurile islands on the basis of petrological features and 14c ages of soils beneath or above the tephra layers three layers were derived from the volcanoes of kunashir island one from mendeleev volcano ca 2 6 cal ka and two from tyatya volcano 1420 cal bp and ad 1973 fourteen widely distributed silicic tephra layers were derived from four volcanoes in hokkaido mashu rausudake tarumai and hokkaido komagatake a widespread tephra was derived from baitoushan volcano between china and north korea fourteen tephra layers have unknown source volcanoes 1 silicic medium k ash 2 silicic low k ash and 11 scoria pumice ash layers except for the medium k ash these tephra are presumed to be derived from the volcanoes in the kurile islands it has been known that caldera forming eruptions occurred at mashu hokkaido and lvinaya past iturup volcanoes in the early holocene ca 12 8 ka however we did not find any tephra from lvinaya past volcano our results provide evidence of the temporal and spatial evolution of eruptive activity in the southern kurile arc we conclude that the level of the eruptive activity in the southern kurile islands especially kunashir island has been lower than that in eastern hokkaido since 8 ka the islands produced mainly vulcanian and strombolian eruptions of mafic magma whereas eastern hokkaido produced plinian eruptions of silicic magma repeated at intervals of 1000 2000 years

flow resistance and sediment transport by concentrated overland flow in a grassland valley abstract flow resistance and sediment transport data are needed from well vegetated humid environments to evaluate surface wash erosion and channel incision by overland flow in humid environments runoff in valley floors can reach depths of several centimetres but erosion is often limited by dense grass cover intense grazing reduces grass cover but the impacts of this on sediment transport processes are poorly understood we conducted flume experiments in a grassed valley of coastal california to investigate flow resistance and sediment yield under natural conditions and with progressive clipping of grass cover flow resistance has a laminar like relationship with reynolds number but we attribute this to very low velocity beneath submerged stems and not to the state of flow the sediment transport relations provide support for the concept of a threshold shear stress below which erosion is effectively prevented by surface resistance shear stress partitioning suggests that on a densely grassed surface over 90 of flow resistance is exerted on plant stems this effectively prevents sediment transport at boundary shear stresses as high as 1000 1800 dyn cm2 complete clipping of the grass cover reduces the critical shear stress for sediment transport to 11 38 of that under natural conditions continued surface wash erosion and channel initiation are prevented however by strong soil cohesion provided by a dense root mat even with reduction of root density boundary shear stresses of at least 250 430 dyn cm2 are required for channel incision

importance of slope gradient and contributing area for optimal prediction of the initiation and trajectory of ephemeral gullies abstract ephemeral gully erosion rates are controlled by various factors out of which topography plays an important role this study investigates the possibility to predict the location of ephemeral gullies using two topographic attributes only i e local slope gradient s and upslope contributing area per unit length of contour a s an inverse relationship between s and a s in which the relative importance of the area exponent was varied was evaluated as to its performance in predicting the location of ephemeral gullies for three intensively cultivated catchments in the belgian loess belt this model is easily applicable as it only uses information on topography which can be derived from a digital elevation model and land use predicted locations of ephemeral gullies were confronted with the locations recorded over 5 years of field observations for all catchments a high relative area exponent relative to the slope exponent was required to yield good results the optimal relative area exponent ranged from 0 7 to 1 5 however the quality of the prediction did not vary significantly when changing the exponent within this range an average relative area exponent of ca 1 is appropriate for all three study areas and may therefore be proposed for similar areas under similar conditions a striking discrepancy was found between the high relative area exponent required to predict optimally the trajectory of the gullies and the low relative area exponent 0 2 required to identify the spots in the landscape where ephemeral gullies begin this indicates that spots in the landscape where gullies start are more controlled by slope gradient while the presence of concavities control the trajectory of the gullies until the slope gradient is too low and sediment deposition starts no relationship was found between the frequency of the occurrence of ephemeral gullies and the percentage of predicted gully pixels for each frequency class this indicates that frequently occurring gullies at the same location are not easier to predict than accidental gullies

quaternary forest and climate history of hokkaido japan from marine sediments abstract pollen data from quaternary marine sediments deposited in central hokkaido northern japan provide insight into northeast asian vegetation and climatic changes over the last few million years during the early pleistocene coniferous forest dominated by picea and cryptomeria japonica and taiga composed of larix and picea developed under cool wet and cold dry climates respectively strong climatic contrasts are inferred from late pleistocene interglacial and glacial pollen assemblages which precede the last glacial cycle in the former cool temperate broad leaf forest mainly composed of fagus reflects a warmer and wetter climate than now in the latter taiga similar to that now found in northern sakhalin apparently flourished in hokkaido the composition of pollen assemblages correlated with oxygen isotope stage 5 changed from cool temperate forest of quercus ulmus and juglans substage 5e to picea larix taiga substage 5d cool temperate forest of quercus and ulmus substage 5c and picea abies forest substage 5b compared with present conditions climate during stage 5 in northern japan apparently fluctuated from warmer wetter to colder drier taiga composed of picea pinus and larix indicating colder dry conditions during stage 4 was replaced by picea abies forest and picea larix taiga in stage 3 suggesting relatively cool and cold dry environments taiga and mixed forest with taiga and cool temperate components characterize stage 2 holocene forests with juglans betula and quercus juglans were succeeded by picea and abies during the early holocene warm interval 7000 bp subsequently quercus ulmus and abies alnus assemblages reflect climatic deterioration pan mixed forest has been developed in hokkaido since 2000 bp

how long is a hillslope hillslope length is a fundamental attribute of landscapes intrinsically linked to drainage density landslide hazard biogeochemical cycling and hillslope sediment transport existing methods to estimate catchment average hillslope lengths include inversion of drainage density or identification of a break in slope area scaling where the hillslope domain transitions into the fluvial domain here we implement a technique which models flow from point sources on hilltops across pixels in a digital elevation model dem based on flow directions calculated using pixel aspect until reaching the channel network defined using recently developed channel extraction algorithms through comparisons between these measurement techniques we show that estimating hillslope length from plots of topographic slope versus drainage area or by inverting measures of drainage density systematically underestimates hillslope length in addition hillslope lengths estimated by slope area scaling breaks show large variations between catchments of similar morphology and area we then use hillslope length relief structure of landscapes to explore nature of sediment flux operating on a landscape distinct topographic forms are predicted for end member sediment flux laws which constrain sediment transport on hillslopes as being linearly or nonlinearly dependent on hillslope gradient because our method extracts hillslope profiles originating from every ridgetop pixel in a dem we show that the resulting population of hillslope length relief measurements can be used to differentiate between linear and nonlinear sediment transport laws in soil mantled landscapes we find that across a broad range of sites across the continental united states topography is consistent with a sediment flux law in which transport is nonlinearly proportional to topographic gradient

the role of global and local factors in determining the middle to late holocene environmental history of the south kurile and komandar islands northwestern pacific abstract the study of holocene deposits from northwestern pacific islands is very important for understanding the natural development of the area in the context of oceanic climate strong microclimate variability and the influence of contrasting marine currents holocene sections from bering island record the following events cooling at about 4600 4500 yr bp warming at about 3500 3400 yr bp cooling at about 3000 yr bp sea level rise up to 1 5 m at about 2700 bp cooling at about 1800 1400 yr bp and sea level rise at about 1000 yr bp on the south kuriles a dry and cool climate changed to warm and moist about 7000 6500 yr bp later than on hokkaido island at this time the kuroshio current system became more active and birch assemblages were replaced by cool temperate broadleaf forests and mixed coniferous broadleaf forests at the holocene optimum about 6000 yr bp temperate broadleaf forest occupied almost all of kunashir and the okhotsk side of iturup and the climate was warmer than present the highest sea level position reached was 2 5 3 m above present level about 6500 6300 yr bp during the cooling about 4700 4500 yr bp island vegetation changed slightly due to the influence of warm currents major sea level regression during this period led to the formation of extensive coastal dune fields the warming at the beginning of the late holocene was almost as great as that of the holocene optimum two minor transgressions are recorded the vegetation changes and climatic deterioration that took place in the second half of the late holocene resulted in either a disappearance of thermophylous taxa or in a southward shift of their natural habitats during the cooling from 1700 to 1300 yr bp the isthmus area increased coastal wetlands with lakes and coastal dunes with paleosols were formed and grassland and swamp landscapes developed late holocene warming was not intensive volcanic impact on environments led to changes in vegetation assemblage swamping of the area and thick soil profile formation

effects of digital elevation model accuracy on hydrologic predictions abstract the effect of vertical accuracy of digital elevation models dems on hydrologic prediction accuracy was evaluated by comparing three dems and associated streamflow simulations for the 7 2 km 2 usda ars watershed at mahantango creek pa the dems were the standard 30 m usgs 7 5 dem a 5 m product derived from low altitude aerial photography and a 30 m product derived from interferometric processing of spaceborne imaging radar c sir c statistical analysis of the dems showed that the usgs dem had the typical stipling errors resulting from processing of the source digital contour maps and a vertical error structure related to the topographic attributes of the watershed the sir c dem had a vertical offset of about 50 m from the high resolution and usgs dems as well as error features that were somewhat related to topographic features inaccuracies in both the usgs and sir c dems were apparent in the drainage network as well as in spatial images of elevation slope and contributing area comparisons of runoff predicted using a hydrologic model based on the three dems showed that mean annual predicted runoff volumes were 0 3 and 7 0 larger for the usgs and sir c dems respectively as compared to the reference dem much larger differences were apparent in individual hydrographs and the usgs and sir c dems predicted lower peaks and higher base flows than did the reference

differences in topographic characteristics computed from 100 and 1000 m resolution digital elevation model data topographic characteristics computed from 100 and 1000 m resolution digital elevation model dem data are compared for 50 locations representing varied terrain in the conterminous usa the topographic characteristics are three parameters used extensively in hydrological research and modelling slope s specific catchment area as and a wetness index computed as the logarithm of the specific catchment area divided by slope ln as s slope values computed from 1000 m dems are smaller than those computed from 100 m dems specific catchment area and the wetness index are larger for the 1000 m dems compared with the 100 m dems most of the differences between the 100 and 1000 m resolution dems can be attributed to terrain discretization effects in the computation of the topographic characteristics and are not the result of smoothing or loss of terrain detail in the coarse data in general the terrain discretization effects are greatest on flat terrain with long length scale features and the smoothing effects are greatest on steep terrain with short length scale features for the most part the differences in the average values of the topographic characteristics computed from 100 and 1000 m resolution dems are predictable that is biases in the mean values for the characteristics computed from a 1000 m dem can be corrected with simple linear equations copyright 2000 john wiley sons ltd

channel network extraction from high resolution topography using wavelets 1 the availability of high resolution topography from lidar offers new opportunities for objectively extracting the channels directly from a dem using local topographic information instead of inferring them indirectly based on global criteria such as area or area slope threshold relationships here we introduce the use of wavelet filtering to delineate threshold curvatures for defining valleys and threshold slope direction change for defining probable channeled portions of the valleys this approach exploits the topographic signatures uniquely found in high resolution topography and reveals the fuzzy topographic transition in which local weakly convergent areas lie at the transition between hillslopes and valleys

a methodology for calculating the spatial distribution of the area slope equation and the hypsometric integral within a catchment 1 the area slope relationship and the hypsometric curve are well known catchment descriptors the main shortcoming of traditional area slope and hypsometry extraction methods is their limited ability to represent heterogeneity within the catchment here we present a new methodology for explicit calculation of the spatial distribution at a pixel scale within a catchment of the area slope parameters and the hypsometric integral this method allows us to create a quantitative representation of the area slope equation and the hypsometric integral which can potentially be used in a variety of geomorphologic applications the results show that the spatial distribution of both the area slope equation and the hypsometric integral are noisy at the pixel scale in order to reduce the noise three averaging techniques were examined subcatchment scale averaging was found to be the best at identifying the spatial distribution of the area slope equation and hypsometric integral at the subcatchment scale the spatial distribution of the area slope equation and the hypsometric integral approximated the spatial distribution of soil morphological and geological units of the goulburn river catchment in eastern australia the spatially distributed area slope results were tested using manually extracted subcatchment average area slope values and found to be well correlated the spatially distributed hypsometric integral was also well correlated with landform concavity and convergence the subcatchment scale averaging of the spatially distributed area slope equation and hypsometric integral is shown to be a promising tool for producing spatially distributed data the techniques are demonstrated on a catchment that has marked spatial variation in soils and geology the results show that the spatially explicit maps can potentially identify the spatial extent of these soil types and geological features and agrees well with existing soil maps

effects of digital elevation model map scale and data resolution on a topography based watershed model the effects of digital elevation model dem map scale and data resolution on watershed model predictions of hydrologic characteristics were determined for topmodel a topography based watershed model the effects of topography on watershed hydrology are represented in topmodel as the distribution of ln a tan b where ln is the napierian logarithm a is the upslope area per unit contour length and tan b is the gravitational gradient the minimum maximum mean variance and skew values of the ln a tan b distribution were computed from 1 24 000 scale 24k dems at 30 and 90 m resolutions and from 1 250 000 scale 250k dems at 90 m resolution for 71 areas in pennsylvania new york and new jersey an analysis of topmodel showed that model predictions of the depth to the water table the ratio of overland flow to total flow peak flow and variance and skew of predicted streamflow were affected by both the dem map scale and data resolution further topmodel analyses showed that the effects of dem map scale and data resolution on model predictions were due to the sensitivity of the predictions to the mean of the ln a tan b distribution which was affected by both dem map scale and data resolution dem map scale affected the mean of the ln a tan b distribution through its influence on the mean of the ln a distribution which characterizes land surface shape and the mean of ln 1 tan b distribution which characterizes land surface slope dem resolution in contrast affected the mean of the ln a tan b distribution primarily by its influence on the mean of the ln a distribution

the indication of martian gully formation processes by slope area analysis the formation process of recent gullies on mars is currently under debate this study aims to discriminate between the proposed formation processes pure water flow debris flow and dry mass wasting through the application of geomorphological indices commonly used in terrestrial geomorphology high resolution digital elevation models dems of earth and mars were used to evaluate the drainage characteristics of small slope sections data from earth were used to validate the hillslope debris flow and alluvial process domains previously found for large fluvial catchments on earth and these domains were applied to gullied and ungullied slopes on mars in accordance with other studies our results indicate that debris flow is one of the main processes forming the martian gullies that were being examined the source of the water is predominantly distributed surface melting not an underground aquifer evidence is also presented indicating that other processes may have shaped martian crater slopes such as ice assisted creep and solifluction in agreement with the proposed recent martian glacial and periglacial climate our results suggest that within impact craters different processes are acting on differently oriented slopes but further work is needed to investigate the potential link between these observations and changes in martian climate

upstream migrating knickpoints and related sedimentary processes in a submarine canyon from a rare 20 year morphobathymetric time lapse capbreton submarine canyon bay of biscay france abstract the capbreton submarine canyon is a striking feature of the south east of the bay of biscay this canyon forms a deep incision through the continental shelf and slope and displays remarkable structures linked to its present day hydrosedimentary activity its head has been disconnected from the adour river since 1310 ce but remains close enough to the coast to be supplied with sediment by longshore drift gravity processes in the canyon body are abundantly described and documented but activity in the head and the fan of the canyon is poorly constrained furthermore many questions remain regarding the details of processes affecting the head the body and the fan of the capbreton canyon in this work we address the paucity of documentation concerning 1 the temporal evolution of sediment transfer between the head and the deep reaches of the canyon and 2 the interaction between gravity processes and the morphology of the canyon floor including both shaping and feedback mechanisms this study is based on the analysis and comparison of eight multibeam bathymetric surveys acquired in the upper part of the capbreton canyon between 1998 and 2018 in depths ranging 10 320 m below sea level this rare time series exposes the morphological evolution of this outstanding dynamic area over the last 20 years our work shows that much of the changes are located in the canyon floor and head following a period characterized by a unique flat floor thalweg the canyon was affected by an incision with low lateral terraces which resulted in a narrow axial thalweg the deepening of the narrow thalweg was induced by retrogressive erosion according to the presence of upstream migrating knickpoints while low elevation residual terraces formed as the canyon reached a local equilibrium profile the flat thalweg observed in 1998 is likely a result of a partial filling of the canyon thalweg by a substantial emptying of the canyon head and significant mass transfer to the proximal part of the canyon a flat floor thalweg was not observed again in the remaining of our time series since 2010 suggesting a possible quieter working mode of the canyon we also propose the first accurate volume quantification of sediment displacement on the canyon floor our findings underline the alternation of filling and erosive periods in the canyon axis and an unexpected continuous sediment deposition in the canyon head during the last 20 years

radiocarbon dated evidence of worldwide early holocene climate change radiocarbon dated glacial deposits from several different areas of the world indicate that alpine glaciers and ice caps in parts of both the northern and southern hemispheres expanded in response to climate change in early holocene time these data suggest that a worldwide episode of cooler climate similar in scope to the more recent neoglaciation occurred ca 8 500 7 500 yr b p

experiments on upstream migrating submarine knickpoints abstract laboratory studies are commonly used to improve our understanding of physical processes that are very difficult or almost impossible to investigate in their natural settings erosion impacts on large scale submarine morphology are good examples we present the results of a preliminary laboratory study focused on submarine knickpoints which are bed depressions bounded by steep walls upstream and a gentle slope downstream originated by the passage of a turbidity current over an erodible bed eight experiments using different materials were performed in a facility capable of running continuous turbidity currents the sediments used in these experiments were kaolin clay two different silica flours and fine sand silica flours and fine sand were each used as single sediments in four experiments the other four experiments were performed using a mixture of these sediment types the bed deposit was formed by a net depositional turbidity current the total sediment concentration by volume in the experiments was 5 in one experiment and 10 in the other seven the discharge ranged from 0 009 to 0 055 l s each experiment started with an initial slope in the channel bed of 15 8 53 as the experiments progressed the bed deposit inside the flume built up knickpoints were observed in four of the eight experiments knickpoints formed under a wide variety of conditions they were found when one material or a combination of materials was used in the tests and when the turbidity current was partially and totally distributed over the channel measured width of the bed depressions ranged from 2 to 4 cm length ranged from 3 to 6 cm and the estimated maximum depth was close to 0 5 cm calculations of the speed of upstream migration indicate values in the vicinity of 0 5 mm s upscaled geometric dimensions based on these laboratory experiments fairly reproduce bed depressions observed on a field scale in earlier studies these laboratory observations suggest that the body of the turbidity current is responsible for the upstream migration of the knickpoint

on the effect of digital elevation model accuracy on hydrology and geomorphology this study compares published cartometric and photogrammetric digital elevation models dems of various grid spacings with a ground truth data set obtained by ground survey and studies the implications of these differences on key hydrologic statistics inferred catchment sizes and stream networks from published dems were found to be significantly different than those from the ground truth in most instances furthermore the width functions and cumulative area relationships determined from the published dems were found to fall consistently outside the 90 confidence limits determined from the ground truth for more than 60 of the relationship suggesting that these hydrologic properties are poorly estimated from published dems however the slope area relationships determined from published dems were found to be less sensitive to catchment shape size and stream network with the relationship falling outside the 90 confidence limits for less than 40 of the relationship for all catchments identified from the published dems a published relationship linking the horizontal resolution with the vertical accuracy of the dem was tested predicting a horizontal resolution of about 10 m for the published dems tested

predicting the topographic limits to a gully network using a digital terrain model and process thresholds a digital terrain model is used with process thresholds to predict the extent of a stable gully network in a 5 km2 catchment of the southeastern highlands of australia the model developed by dietnch et al 1992 1993 predicts the topographic controls on channel networks and interprets these in terms of a critical shear stress for channel incision c applied by saturation overland flow we adapt the model slightly to compare the shear stress applied by hortonian overland flow to that applied by saturation overland flow the limits to gully erosion in the catchment are controlled strongly by a topographic threshold that has an inverse relationship between upslope catchment area and local gradient the topographic threshold for channel incision is reproduced using a simple model of hortonian overland flow and a c appropriate for incision into a degraded grass surface c 245 dyn cm2 this is consistent with historical evidence for the timing of gully erosion the study confirms a strong topographic control on the extent of the channel network in a catchment significantly different from the western north america catchments where the topographic threshold was first demonstrated despite its simplicity the model for incision by overland flow appears capable of distinguishing the hydrological processes responsible for channel incision when these are reflected in the relationship between channel network and landscape morphology the model requires relatively simple inputs suggesting it may be useful for mapping gully erosion hazard in actively eroding catchments

road surface drainage channel initiation and slope instability field surveys of road drainage concentration at three sites in the western united states are used to test simple models relating channel initiation and shallow landsliding to ground slope and contributing area thresholds the form of boundaries between data for locations where road drainage concentration is associated with either shallow landsliding channel initiation by overland flow or no observable geomorphic effect is consistent with theoretically derived drainage area slope relations comparison of survey data with results of previous studies in these areas indicates that the drainage area required to support a channel head is smaller for road related runoff than for undisturbed slopes contrary to current land management paradigms in the pacific northwest drainage concentration from ridgetop roads may cause both landsliding and integration of the channel and road networks road drainage concentration increases the effective length of the channel network and strongly influences the distribution of erosional processes in each of the study areas the approach of using field reconnaissance to establish thresholds for erosion associated with road drainage provides a useful method to define regional criteria for road design that should reduce impacts on downstream channel systems

paleoenvironments and landscape history of the minor kuril islands since the late glacial abstract the problems of vegetation development of the minor kuriles since the last glacial maximum are discussed the size of island land and relief features influenced landscape development under post glacial holocene climatic changes and sea level oscillations the results suggest that isolation had a great role on development of the landscapes low flat relief active wetlands and the cooling influence of the ocean were the main factors in the development of grassland and wetland landscapes on small islands in the late holocene forest vegetation was preserved only on shikotan island which has upland relief the appearance of broad leaved genera and the disappearance of some taxa are discussed

use of a landscape simulator in the validation of the siberia catchment evolution model declining equilibrium landforms this paper presents a study to test the ability of the current generation of landscape evolution models to correctly predict landscape form from measured erosion processes landscapes generated by the siberia landscape evolution model were compared to experimental model landscapes in declining equilibrium the model simulations were compared using geomorphologically and hydrologically significant parameters comparisons of the simulated landscapes with the experimental landscapes were carried out using the hypsometric curve width function cumulative area distribution and area slope relationship these comparisons demonstrate that siberia can correctly simulate the experimental model landscape at declining equilibrium the simulation showed sensitivity to the spatial distribution of the rainfall particularly with respect to hypsometry using the correct measured distribution of rainfall was necessary rather than using a spatially uniform rainfall distribution the results also highlighted the importance of digital terrain map dtm error in deriving geomorphic statistics the observed landform had a consistently larger width function than the simulation only when the simulations were corrupted with elevation errors with statistical properties of the errors in the experimental landscape dtm as measured by photogrammetry did the observed and simulated width functions match

high resolution quantification of gully erosion in upland peatlands at the landscape scale the upland peatlands of the uk are severely eroded with large areas affected by gully erosion the peatlands are important areas of carbon storage and provide a range of other ecosystem services including water supply and biodiversity all of which are negatively impacted by erosion of the upland surface the magnitude of the gully erosion and consequent adjustment of the peatland morphology is such that in degraded peatlands the extent and magnitude of erosion is a major control on peatland function accurate mapping of gully form is therefore a necessary precondition to the understanding and management of these systems this paper develops an approach to extracting gully maps from high resolution digital elevation models dems gully maps of the bleaklow plateau in northern england were derived from a 2 m lidar dem by combining areas of low difference from mean elevation and high positive plan curvature gully depth was modelled by interpolating between gully edges testing of the gully mapping and depth modelling against aerial photography manual interpretation of the dem and ground survey revealed that gully plan form is well represented and gully width and depth are modelled with tolerances close to the horizontal and vertical resolution of the lidar imagery estimates of gully width and depth were less reliable for gullies with total width of less than four pixels the approach allows for the first time the derivation of accurate estimates of gully extent and magnitude over large areas and provides the basis for modelling a range of processes controlled by gullying the approach has wider applicability to mapping gully erosion in a wide range of environments copyright 2010 john wiley sons ltd

the importance of spatially heterogeneous erosivity and the cumulative area distribution within a basin evolution model abstract topography reflects the terrain composition and the forces to which it is exposed the elements that control this shape are intuitive precipitation wind soil composition geologic activity lithology and vegetation each of these elements varies naturally in space a model of basin evolution is shown to produce quantitatively different topography for different relative magnitudes of diffusive and incisive erosion processes spatial heterogeneities in erosivity also influence the simulated topography the calibration of this evolution model is compared to observed topography the calibration process ultimately hinges on quantification of the aggregation pattern of the basin through analysis of the cumulative area distribution the effect of spatially heterogeneous erosivity is shown to be crucially important to reproduce the cumulative area distribution of observed topography

effects of vertical resolution and map scale of digital elevation models on geomorphological parameters used in hydrology the advent of digital elevation models dems has made it possible to objectively extract calculate and store geomorphological parameters for hydrological modelling at several scales for a grid based dem the threshold area used to extract the channel network is analogous to the scale of the map produced in addition to the map scale the effects of the vertical resolution of the dem on some frequently used geomorphological parameters in hydrology are examined using high resolution dems of two natural and two artificial catchments the vertical resolution was varied between 1 cm and 1 m the most common vertical resolution of dems at a fixed map scale the mean absolute percentage error in the geomorphological parameters caused by a decrease in vertical resolution is within the range 0 5 for the medium sized catchments and 0 10 for the small catchments studied although it is true that a change in vertical resolution may cause a change in the individual pixel slope area and topographic index area slope particularly in low relief terrain their cumulative distributions do not show any significant change with the vertical resolution the shape of the normalized width function is not very sensitive to the vertical resolution and the map scale for small catchments order change may occur at different map scales for the different vertical resolution dems of the same catchment causing a significant change in order related parameters such as horton ratios it is suggested that the vertical resolution of the dem of a catchment be considered satisfactory for most hydrological applications if the ratio of the average drop per pixel and vertical resolution is greater than unity this ratio criterion could be used to define the minimum pixel area for reliable channel network definition for any given vertical resolution the minimum pixel area places a lower bound on the horizontal resolution with which a channel network can be extracted from a dem these results could potentially be used to assess the adequacy for hydrological purposes of existing and proposed digital elevation databases

experiments on hydraulic jumps in turbidity currents near a canyon fan transition the point at which a submarine canyon debouches on its associated abyssal fan is generally characterized by a drop in channel slope turbidity currents of the kind responsible for the genesis of the canyon and fan should display an internal hydraulic jump near the slope transition no direct field observations of any such jump appear however to have been made experiments on the nature of the jump and the resulting sedimentary deposits indicate that the thickness of the deposits just downstream of the jump tends to increase as the ratio of bed shear velocity immediately behind the jump to particle fall velocity decreases

cyclic steps review and aggradation based classification abstract cyclic steps are a type of upper flow regime bedform consisting of trains of upstream and upslope migrating bed undulations the overriding flow is characterised by a series of hydraulic jumps occurring in the troughs of the undulations cyclic steps form in open channel flows such as rivers and comprise a common bedform in subaqueous density flows in oceans lakes and reservoirs cyclic steps are associated with alternating froude subcritical and froude supercritical flow on respectively the stoss side and lee side of individual bedforms the transition between these flow states is embodied by the hydraulic jump in the trough of the bedform leading to the permanent or quasi permanent morphology of cyclic steps over the past decade numerous studies affirmed the dominant role of cyclic steps in generating bed undulations in modern and ancient glacial outwash fluvial delta and turbidite environments as reviewed here cyclic steps were previously discriminated as net depositional climbing transportational and net erosional falling in different parts of sedimentary systems the following cyclic step descriptors with distinct depositional signatures are proposed fully depositional partially depositional transportational partially erosional and fully erosional partially depositional cyclic steps are most common they are associated with backset bedded sets high aggradation rate and nested scours filled with massive to backset bedded deposits low aggradation rate the new classification can be used as a predictive tool in the reconstruction of modern and ancient sedimentary successions using repeat bathymetry seismic reflection or outcrop data it is applied in three turbidite case studies classical deep sea system small scale delta slope and line sourced carbonate slope

spatial resolution sensitivity of catchment geomorphologic properties and the effect on hydrological simulation the geomorphologic area function and width function that characterize the forms of hillslope and river networks are two key parameters employed in the gbhm geomorphology based hydrological model for representing the hydrological processes together with other spatial information one fundamental issue on the use of the geomorphologic properties is the spatial resolution sensitivity in both the threshold area for river network generation and digital elevation model dem resolution the threshold area is the minimum drainage area required to initiate the river the dem resolution depends on the available elevation data in the present study multifractal analysis was used to investigate the sensitivity of width functions extracted by different threshold areas and the sensitivity of area functions extracted from various resolutions of dems fifteen japanese catchments were selected for the sensitivity analysis based on 250 m mesh dem data it was found that the river networks generated with larger threshold areas tend to lose the detailed scaling information when the dem mesh size increases the river networks extracted with the same threshold area become sparser and the topography tends to be flat and scaling structures of the area functions become simpler the runoff generations of the gbhm were influenced by the dem resolution the effect of the dem resolution on the hydrological response is related to the temporal resolution with more influence on the hourly response compared with the daily response from the relation between the scaling structure expressed by the multifractal spectrum and the hydrological response of a catchment it was found that the detailed scaling information had more effect on the hydrological response of higher temporal resolution copyright 2001 john wiley sons ltd

morphological evolution of a well constrained subaerial subaqueous source to sink system wabush lake since 1964 the iron ore company of canada has deposited iron tailings resulting from mining operations into wabush lake western labrador canada this activity has resulted in a continuous hyperpycnal flow flowing over the lake floor bathymetric surveys were carried out between 1999 and 2008 as part of the overall environmental iron ore company of canada plans to maintain safe disposal strategies of tailings into the lake here this dataset is used to study the evolution of different channels present in wabush lake and their link with knickpoints found at the head of most of these channels the channels show notable evolution from one survey to the next some knickpoints and channels may be followed throughout more than one survey the evolution of these knickpoints is the process responsible for the creation of erosional channels the context in which they appear as well as the evolution of some of the subaqueous channels is analysed cyclic steps and sediment waves are also found in the lake these rhythmic bedforms also created by the passage of turbidity currents are analysed sediment waves found in wabush lake show values for both wavelength and wave height that are approximately one order of magnitude smaller than most of those found in the marine environment

hydraulic jumps in sediment driven bottom currents laboratory experiments were conducted to observe the behavior of turbidity currents in the vicinity of a slope transition both sediment laden and saline hydraulic jumps were produced the vertical structure of the currents was found to depend on flow regime the saline and turbid hydraulic jumps showed similar characteristics the amount of water entrained by the flows through a jump was small the change in flow regime caused a marked reduction of the bed shear stress downstream of the jump in nature a turbidity current experiencing a hydraulic jump will drop most of its bedload immediately downstream from the jump while the suspended load will respond more gradually to the change in flow regime and will deposit sediment over a distance far exceeding 1 000 times the jump height

spatial distribution of channel heads in the polish flysch carpathians article i nfo one of the key topics in modern geomorphology is the identification of locations where the drainage network begins however there still exists a gap in the research literature in the area of channel head location in flysch regionscharacterizedbyunique hydrogeological conditions in thisstudy we haveidentifiedthe spatial distribu tionofchannelheadsanddeterminedthresholdvaluesofmorphometricparametersforcatchmentscontributing to channel heads in the polish flysch carpathians we surveyed a total of 401 channel heads on the main ridge of the polonina wetlinska range using gps the dem was used to identify 16 physiographic parameters for each catchment and statistical correlations between catchment parameters were also calculated we compared field data versus the drainage network produced using a topographic map and dem the channel head density based on field mapping is five times higher than the density estimated using a topographic map and 250 lower than that obtained from a dem most channel heads are recharged by very small catchment areas the threshold value for catchment size has been shown to be about 0 01 km 2 the mean slope gradient responsible for channel head formation is 18 in the study area given the very small size of catchment areas contributing to channel heads in the study area remote sensing methods are not useful fieldwork is still the best method of mapping channel heads the distribution of channel heads across the polonina wetlinska range in the polish flysch carpathians cannot be described using simple relationships correlations between topographic attributes that are common in other physiographic regions are not very clear in flysch areas

three dimensional landscape process modelling the effect of dem resolution many landscape models have been developed over the past decades however relatively little is known about handling the effects of changing spatial and temporal resolutions therefore resolution effects remain a factor of uncertainty in many hydrological and geomorphological modelling approaches in this paper we present an experimental multi scale study of landscape process modelling emphasis was laid on quantifying the effect of changing the spatial resolution upon modelling the processes of erosion and sedimentation a simple single process model was constructed and equal boundary conditions were created using artificial digital elevation models dems eliminated effects of landscape representation the only variable factors were dem resolution and the method of flow routing both steepest descent and multiple flow directions our experiments revealed an important dependency of modelled erosion and sedimentation rates on these main variables the general trend is an increase of erosion predictions with coarser resolutions an artificial mathematical overestimation of erosion and a realistic natural modelling effect of underestimating resedimentation cause this increasing the spatial extent eliminates the artificial effect while at the same time the realistic effect is enhanced both effects can be quantified and are expected to increase within natural landscapes the modelling of landscape processes will benefit from integrating these types of results at different resolutions

despeckling srtm and other topographic data with a denoising algorithm abstract noise in topographic data obscures features and increases error in geomorphic products calculated from dems dems produced by radar remote sensing such as srtm are frequently used for geomorphological studies they often contain speckle noise which may significantly lower the quality of geomorphometric analyses we introduce here an algorithm that denoises three dimensional objects while preserving sharp features it is free to download and simple to use in this study the algorithm is applied to topographic data synthetic landscapes srtm topsar and the results are compared against using a mean filter using lidar data as ground truth for the natural datasets the level of denoising is controlled by two parameters the threshold t that controls the sharpness of the features to be preserved and the number of iterations n that controls how much the data are changed the optimum settings depend on the nature of the topography and of the noise to be removed but are typically in the range t 0 87 0 99 and n 1 10 if the threshold is too high noise is preserved a lower threshold setting is used where noise is spatially uncorrelated e g topsar whereas in some other datasets e g srtm where filtering of the data during processing has introduced spatial correlation to the noise higher thresholds can be used compared to those filtered to an equivalent level with a mean filter data smoothed by the denoising algorithm of sun et al sun x rosin p l martin r r langbein f c 2007 fast and effective feature preserving mesh denoising ieee transactions on visualisation and computer graphics 13 925 938 are closer to the original data and to the ground truth changes to the data are smaller and less correlated to topographic features furthermore the feature preserving nature of the algorithm allows significant smoothing to be applied to flat areas of topography while limiting the alterations made in mountainous regions with clear benefits for geomorphometric analysis in areas of mixed topography the results of denoising on the derived flow accumulation and slope maps particularly when compared to the results of mean filtering demonstrate the usefulness of the algorithm in fields such as hydrological modelling and landslide prediction

channel head location and characteristics using digital elevation models the drainage network is the conduit through which much surface water and sediment are routed within a catchment in a catchment the position of where hillslopes begin and channels end has long been considered the position of transition between diffusive processes upslope and the more incisive fluvial processes downslope consequently understanding channel head location is an important issue in understanding catchment hydrology and geomorphology this study examines channel head position and characteristics in a catchment in arnhem land northern territory australia in this study the position of channel heads was mapped within the catchment and plotted on a reliable digital elevation model of the catchment it was found that the majority of channel heads have relatively small source areas and that graphical catchment descriptors such as the area slope relationship and cumulative area distribution can provide reliable measures of the field position of the heads of first order streams and the transition from hillslope to channel the area slope relationship and cumulative area distribution are also shown to be good tools for determining digital elevation model grid size which can capture hillslope detail and the transition from hillslope to channel copyright 2005 john wiley sons ltd

multiproxy record of late holocene climatic changes and natural hazards from paleolake deposits of urup island kuril islands north western pacific abstract the evolution of the late holocene environments has been reconstructed on the basis of multiproxy studies of peat sequences the vegetation response to short period climate fluctuations has been traced early in the late holocene there were birch forests with oak and other broadleaf trees vast areas were occupied by forb meadows under cooling 3250 yr bp the shrub pine pinus pumila became the landscape forming species and since 2490 yr bp selaginella selaginoides appeared in abundance the little ice age was marked by the disappearance of broadleaf trees and widely spread heath land communities the higher stands of the lake level were related to warmings 3660 3590 3450 3180 2960 2840 2410 2260 cal yr bp shallowing coincided with short term coolings 3590 3450 3180 2960 2840 2410 2260 2150 cal yr bp marked by reduced precipitations the dune ridge formation began during the longest cooling accompanied by a minor regression the dunes were stabilized and a paleosol developed 2340 2260 yr bp a younger generation of eolian sands developed during the little ice age an ecological effect of volcanic ashfalls has been estimated the local biotic components seem to have been most afflicted by the eruption in the north of iturup in 2100 2300 cal yr bp when ckr tephra up to 30 cm thick was deposited the ages of 4 strongest tsunamis that occurred over the last 3660 years were determined they appeared to be related to the earthquakes with focuses close to urup island or south of it the lake microflora shows ecological effect of the marine water invasions

new pollen records of late pleistocene and holocene changes of environment and climate in the lower amur river basin ne eurasia abstract the late pleistocene holocene paleoclimate and paleoenvironmental changes of the lower amur basin are presented based on pollen records from radiocarbon dated peat sections the gur section represents the most complete terrestrial record of the russian far east and probably for all of northeast asia landscape changes are reconstructed for warm events corresponding to the bolling and allerod and cold episodes as middle dryas and younger dryas in europe there were three warm periods in the lower amur basin 8900 8300 5000 5700 and 3200 4200 bp a major expansion of diverse species in the forest formations in the entire lower amur river basin occurred at 5000 5700 bp changes and developments of paleoclimate events and paleoenvironmental changes of late pleistocene and holocene in lower amur basin were correlative with european climate events

effects of digital elevation model resolution on derived stream network positions 1 this study examines the effect of digital elevation model dem resolution on the positional accuracy of derived hydrologic networks and quantitatively confirms that dem resolution should be greater than the average hillslope length when used for hydrologic modeling seven hundred kilometers of mapped stream networks are compared to stream networks derived from 17 dems with resolutions ranging from 30 m to 3 km comparison between predicted and mapped streams reveals that accuracy of predicted stream locations decays quickly beyond a dem resolution of 180 m a new application of gyasi agyei et al s 1995 dem resolution suitability test based on average slope and vertical resolution indicates an average hillslope length of between 150 and 180 m tarboton et al s 1991 method of determining average hillslope length based on slope and accumulation areas reconfirms the length to be 150 m and verifies the link between network accuracy and hillslope scale two algorithms are used to derive stream networks the d algorithm tarboton 1997 which allows for flow dispersion and the d8 algorithm o callaghan and mark 1984 which does not a comparison between the d8 and d algorithms shows that modeling flow dispersion is not necessary in steep terrain as both algorithms performed equally well however the d algorithm is found to be less susceptible to modeling erroneous hillside flow convergence making it preferable to the d8 algorithm when used by tarboton et al s 1991 method of determining the average hillslope lengths finally field observation indicates that predicted first and second order streams tend to exist when predicted however mapped streams have a higher positional accuracy

use of digital elevation model data for the derivation of the geomorphological instantaneous unit hydrograph the use of digital elevation models dems allows the automatic derivation of channel networks and the quantitative description of the geomorphic characteristics of basins a common method of channel network extraction from dem data is based on the specification of a threshold area at that is the minimum support area required to drain to a point for a channel to form usually an arbitrary constant threshold area value is chosen for channel network extraction in this study the effects of threshold area selection both on the morphometric and scaling properties such as drainage density total channel length horton laws and fractal dimension of a channel network and the associated hydrological response function are analysed the response is obtained following the geomorphological instantaneous unit hydrograph theory two different probabilistic models are used they both relate the characteristic response function of the basin to its dem data derived networks one is derived assuming a strahler stream ordering system and the other is obtained by averaging a flow equation with respect to the network structure described by the width function applications are shown for three mountainous basins in the italian alps a sensitivity analysis is performed to study the influence of the variability of morphometric properties with respect to at on the hydrological response obtained it is shown that the model based on the width function is able to reduce the effects of this variability on the simulated response 1997 by john wiley sons ltd

a physical explanation for an observed area slope elevation relationship for catchments with declining relief a general relationship between the contributing area slope and mean elevation of catchments with relief declining after a tectonic uplift event is presented this relationship is based on the continuity equation for runoff and erosion processes in the catchment the key hypothesis underlying this relationship is that as a catchment declines the nondimensionalized catchment approaches a constant form this hypothesis is verified for computer simulated catchments the area slope elevation relationship covers several cases catchments declining toward a peneplain catchments declining from a high slope dynamic equilibrium resulting from a high rate of tectonic uplift to a low slope one resulting from a lower rate of tectonic uplift and catchments declining from an elevated initial condition as for example in the decline of a mine spoil heap a previously published relationship between slope and area for catchments in dynamic equilibrium and based on runoff and erosion physics is shown to be a special case of this general relationship the new area slope elevation relationship is compared with data from simulated catchments and a field catchment it is thus shown that for declining catchments the area slope elevation relationship is a good predictor of catchment form for catchments with declining relief it is argued that the slope area elevation relationship is sufficient with the planiform drainage pattern to completely define the elevation properties of the catchment such as for instance the hypsometric curve

revisiting the hypsometric curve as an indicator of form and process in transport limited catchment hypsometry has historically been used as an indicator of geomorphic form of catchments and landforms yet there has been little work aimed at relating hypsometry to landform process and scale this paper uses the siberia catchment evolution model to explore linkages between catchment process and hypsometry siberia generates results that are qualitatively and quantitatively similar to observed hypsometric curves for physically realistic parameters however we show that not only does the hypsometry reflect landscape runoff and erosion process but it is strongly dependent on channel network and catchment geometry we show that the width to length ratio of the catchment has a significant influence on the shape of the hypsometric curve though little on the hypsometric integral for landforms dominated by fluvial sediment transport the classic strahler mature hypsometric curve is only generated for catchments with roughly equal width and length narrow catchments show a hypsometric curve more similar to strahler s monadnock form for landscapes dominated by diffusive transport the simulated hypsometric curve is concave down everywhere this being consistent with curves reported for some example catchments in france because the transition between diffusive dominance to fluvial is scale dependent with larger catchments exhibiting greater fluvial dominance then the hypsometric curve is a scale dependent descriptor of landforms experimental results for simulated landforms from a small scale rainfall erosion simulator are reported it is shown that siberia yields satisfactory fits to the data confirming its ability to predict the form of the hypsometric curve from a simple model of geomorphic processes 1998 john wiley sons ltd

results from a new model of river basin evolution this paper briefly describes a model of the erosional development of catchments and their channel networks the model differentiates between the dominant transport processes in hillslope and channels the development of channels and hillslopes occurs in an integrated manner as a function of physically observable mechanisms the growth of a river basin is qualitatively described the model concepts are used to study the basin during periods of growth transient periods as well as during dynamic equilibrium this leads to hypotheses about the relationship between slopes relief tectonic uplift erodability runoff and catchment area it is shown that the model leads to very reasonable and desirable behaviour of hillslopes during retreat and degradation

conditions for the ignition of catastrophically erosive turbidity currents abstract the basic impediment to a clear understanding of eroding and depositing turbidity currents has been the lack of a proper formulation of bed sediment entrainment this problem is addressed herein a detailed analysis indicates that the bagnold criterion is necessary but insufficient for self sustaining turbidity currents the analysis reveals two possible equilibrium states a relatively low velocity ignitive state and a high velocity dense catastrophic state a stability analysis indicates that the ignitive state is unstable flows below it invariably die out and flows above it ignite i e accelerate and entrain sediment to the catastrophic state which is stable the ignitive state thus defines the criterion for a self sustaining turbidity current estimates of the catastrophic state suggest that it is highly erosive and competent to scour out submarine canyons

a physical explanation of an observed link area slope relationship an observed log log linear relationship between channel slope and contributing area is explained by the erosional physics that lead to catchment form it is postulated that tectonic uplift is in balance with the fluvial erosion down wasting that dominates catchment erosion and it is shown that this relationship results in the observed log log linear relationship at dynamic equilibrium in addition it has been observed that there are deviations from this log log linear relationship near the catchment divide with observed slopes being lower than those predicted from the relationship this is explained by noting that for small areas fluvial erosion effects are dominated by soil creep and rain splash modeled by diffusive physics the area at which this deviation from log log linearity occurs is that point on the hillslope at which diffusive physics like soil creep and rain splash begin to dominate fluvial erosion these predictions are confirmed by numerical simulations using a catchment evolution model

asymmetrical inversely graded upstream migrating cyclic steps in marine settings late miocene early pliocene fish creek vallecito basin southern california abstract cyclic steps are ubiquitous in modern sedimentary environments yet their recognition remains sparse in the rock record here we interpret three sets of undulating backsets 1 to 3 recognized in the late miocene early pliocene latrania formation in the anza borrego desert the fish creek vallecito basin southern california usa as the first cm to dm scale outcrop record of cyclic steps based on asymmetrical cross sections upstream migration and inversely graded laminae upstream migration and asymmetrical cross sections of backsets and concomitant backset laminae are attributed to supercritical to subcritical flow transitions through weak hydraulic jumps which are composed of i thin tens of centimetres and slower reported as flow velocities of 0 45 to 1 45 m s 1 with mean value of 0 89 m s 1 subcritical represented by internal froude numbers fr of 0 67 to 0 99 with mean value of fr 0 84 turbidity currents on the stoss sides and ii thin tens of centimetres and faster reported as of 0 99 to 4 03 m s 1 with mean value of 2 24 m s 1 supercritical represented by fr of 1 84 to 3 07 with mean value of fr 2 42 turbidity flows on the lee sides the inversely graded laminae in the troughs of backsets are 2 to 5 cm thick and consist of two discrete divisions i 1 to 2 cm thick lower finer grained divisions made up of parallel laminated siltstones overlain by very fine to fine grained sandstones and ii 2 to 3 cm thick upper divisions composed of medium to coarse grained sandstones with sporadic occurrence of subrounded pebbles these inversely graded laminae are related to stratified collisional and or frictional traction carpets under conditions of high fall out rates due to the poor preservation potential of cyclic steps the rock record of cyclic steps is generally considered to be rare the present outcrop based study presents a detailed analysis of sedimentary facies growth patterns and flow dynamics of marine cyclic steps thereby contributing to better understand architectural styles and lithological properties of cyclic steps in the geological record

evaluation of digital channel network derivation methods in a glaciated subalpine catchment the digital elevation model dem has become an essential tool for an increasing array of mountain runoff analyses particularly the derivation and mapping of stream channel networks this study examines how well commonly applied dem based channel derivation methods at different spatial resolutions can represent the channel network for a glaciated rocky mountain headwater catchment the specific objectives are to 1 examine how differences in gridded dem resolution affect spatially distributed values of local slope specific contributing area and topographic wetness index derived from both eight and infinite directional flow algorithms 2 map the actual stream channel network to examine the influence of surface variables on channel initiation and 3 assess accuracy of dem derived networks compared with the field surveyed network results show that for the same contributing area threshold increasing grid cell size leads to increased channelization of modeled networks a plot of local slope versus contributing area reveals a negative relationship similar to that of prior studies in un glaciated areas but with breaks in slope at contributing areas that are too small to represent thresholds for channelization field survey results and evaluation of dem derived channel networks suggest that channel network formation is not clearly related to surface topographic variables at loch vale digitally derived channel networks do not accurately predict low order channel locations but approximations of the channel network with drainage density and headward extent of channelization similar to the observed network can be derived with both a 1 m and 10 m dem using a contributing area threshold of approximately 4x104 m2 copyright 2014 john wiley sons ltd

slope area relationships and sediment dynamics in two alpine streams the paper focuses on the channel network of alpine basins attempting to interpret channel reaches in terms of response to erosion and deposition processes two basins in the dolomites north eastern italy were considered the rio cordon 5 km2 and the upper boite river 163 km2 the channel network was extracted from raster type digital elevation models dem using a slope area threshold criterion a contribution area index cai which combines drainage area a and local slope s cai a0 5s was used to identify channel heads the channel network extracted from the dem was then analysed to recognize cells showing a value of cai lower than the threshold adopted for channel initiation contiguous cells with low values of cai define channel reaches with low transport efficiency field surveys carried out for some selected cases showed a good agreement between prevailing sediment deposition predicted by the analysis of the channel network and observed channel morphological features sediment sources mapped in two study basins were also analysed in relation to the location of channels with high potential for sediment deposition this made it possible to classify the potential role of different types of sediment sources with regard to basin sediment yield topographic characteristics of the channel network expressed by cai were compared with a classification of channel morphology in the rio cordon it was found that cells with low values of cai frequently occur in the riffle pool reaches whereas the percentage significantly decreases in step pool and bedrock channels copyright 2003 john wiley sons ltd

holocene climatic changes and environmental history of iturup island kurile islands northwestern pacific the study of holocene deposits on iturup island is very important for understanding palaeolandscape changes on the island it is separated by deep straits from the neighbouring islands and was isolated during the last glacial maximum landscape changes over the last 40000 years and the role of refugia on vegetation development are discussed changes in natural processes in this region were controlled both by global climatic changes and by regional factors birch forests developed at the warming about 36 37 ka ago whereas tundrapark landscape developed with the cooling of the last glacial maximum holocene environments reflect climatic changes and sea level oscillations the fluctuation of warm and cold currents influenced the landscape development at the holocene optimum about 6 ka broadleaved forests with quercus phellodendron carpinus juglans fagus fraxinus and syinga occupied the okhotsk side of central iturup climate was warmer than present and the sum of active tempe ratures 10 c was n

holocene and deglacial ocean temperature variability in the benguela upwelling region implications for low latitude atmospheric circulation 1 mg ca analyses of g bulloides and abundances of n pachyderma left coiling from ocean drilling program odp leg 175 hole 1084b in the benguela coastal upwelling system document lower sea surface temperatures during the last glacial maximum lgm younger dryas mid holocene and little ice age in the southeastern atlantic taking into consideration the possible effects of differential carbonate dissolution the mg ca data indicate younger dryas temperatures 2 3 c cooler than those of the early holocene and lgm temperatures 4 5 c cooler than those of the early holocene the cool interval during the deglacial period at hole 1084b matches the timing of younger dryas shifts in cariaco basin and greenland ice sheet records and that of a nearby alkenone record comparison of mid holocene cooling at hole odp1084b with other high resolution records of holocene and last deglacial sea surface temperatures from the tropical atlantic implies consistent basin wide changes in atmospheric circulation a brief period of 1 5 2 c cooling between 17 8 and 17 2 ka if related to heinrich event 1 is consistent with a previously hypothesized tropical origin of all heinrich climate change events

testing of the siberia landscape evolution model using the tin camp creek northern territory australia field catchment the siberia landscape evolution model was used to simulate the geomorphic development of the tin camp creek natural catchment over geological time measured hydrology erosion and geomorphic data were used to calibrate the siberia model which was then used to make independent predictions of the landform geomorphology of the study site the catchment located in the northern territory australia is relatively untouched by europeans so the hydrological and erosion processes that shaped the area can be assumed to be the same today as they have been in the past subject to the caveats regarding long term climate fluctuation a qualitative or visual comparison between the natural and simulated catchments indicates that siberia can match hillslope length and hillslope profile of the natural catchments a comparison of geomorphic and hydrological statistics such as the hypsometric curve width function cumulative area distribution and area slope relationship indicates that siberia can model the geomorphology of the selected tin camp creek catchments copyright 2002 environmental research institute of the supervising scientist commonwealth of australia

comparison of slope estimates from low resolution dems scaling issues and a fractal method for their solution five different algorithms for calculating slope from digital elevation models dems have been compared from regional to global scales though different methods produce different results the most significant outcome is that slope varies inversely with the dem grid size thus slopes estimated from coarse resolution data can be considered to produce significant underestimates of the true slope a fractal theory is adapted to solve this problem the variogram technique for the definition of fractal parameters is demonstrated to provide a relationship between slope and the spatial resolution of measurement the variation of fractal parameters is discussed at various scales and a model is developed to estimate the high resolution slope based on the coarse resolution dem by using fractal parameters the fractal parameters are estimated from the standard deviation of elevation in a 3 3 window of the dem to account for local variability in the surface standard deviation of elevation is found to be the most invariant property of different scale dems of the same area the model is validated using different resolution dems in southern spain and it is used to estimate the high resolution slope values at global scales based on a coarse resolution dem the slopes estimated using the technique outlined are a significant improvement on those estimated directly from the coarse resolution data slopes estimated in this way allow the more effective use of available coarse resolution data in regional and global scale modelling studies copyright 1999 john wiley sons ltd

a catchment scale evaluation of the siberia and caesar landscape evolution models landscape evolution models provide a way to determine erosion rates and landscape stability over times scales from tens to thousands of years the siberia and caesar landscape evolution models both have the capability to simulate catchment wide erosion and deposition over these time scales they are both cellular operate over a digital elevation model of the landscape and represent fluvial and slope processes however they were initially developed to solve research questions at different time and space scales and subsequently the perspective detail and process representation vary considerably between the models notably caesar simulates individual events with a greater emphasis on fluvial processes whereas siberia averages erosion rates across annual time scales this paper describes how both models are applied to tin camp creek northern territory australia where soil erosion rates have been closely monitored over the last 10 years results simulating 10 000 years of erosion are similar yet also pick up subtle differences that indicate the relative strengths and weaknesses of the two models the results from both the siberia and caesar models compare well with independent field data determined for the site over different time scales representative hillslope cross sections are very similar between the models geomorphologically there was little difference between the modelled catchments after 1000 years but significant differences were revealed at longer simulation times importantly both models show that they are sensitive to input parameters and that hydrology and erosion parameter derivation has long term implications for sediment transport prediction therefore selection of input parameters is critical this study also provides a good example of how different models may be better suited to different applications or research questions copyright 2010 john wiley sons ltd and commonwealth of australia

gully erosion a comparison of contributing factors in two catchments in south africa abstract gully erosion is an environmental agricultural and social problem requiring extensive research and mitigation actions to control this study assesses the influence of factors contributing to gully erosion using geographic information system gis and information value infval statistics from two catchments coded x12 and w55 in the mpumalanga province of south africa existing spatial data representing contributing factors soil geology vegetation and land use were analyzed topographic variables were extracted from a 10 m digital elevation model dem interpolated from map contours and gullies were mapped from aerial photos with 0 5 m spatial resolution a zonal approach was used to extract the proportion of gullies in each of the contributing factor classes using gis software packages and infval weighting was performed to determine the influence of each class comparison of the results shows the variation in the level of influence of factors contributing to gully erosion the findings in catchment x12 support a commonly held assumption that gully formation is influenced by duplex soils underlain by colluvium and alluvial deposits on a lower slope position where overland flow converges and accumulates resulting in high soil moisture gullies were also influenced by soils developed over weathered granite gneiss and ultramafic rocks the influence of a granite rock was further highlighted in catchment w55 where there is a variable thickness of very deep hutton dominant soil form and shallow lithosols with sandy texture on an area of moderate to steep slopes where overland flow converges and accumulates with high stream power in overgrazed grassland an understanding of these factors will assist future modelling of the vulnerability to gully erosion over a wider geographical area