persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis with application to volcan alcedo galapagos 1 while conventional interferometric synthetic aperture radar insar is a very effective technique for measuring crustal deformation almost any interferogram includes large areas where the signals decorrelate and no measurement is possible persistent scatterer ps insar overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms existing ps methods have been very successful in analysis of urban areas where stable angular structures produce efficient reflectors that dominate background scattering however man made structures are absent from most of the earth s surface furthermore existing methods identify ps pixels based on the similarity of their phase history to an assumed model for how deformation varies with time whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study we describe here a method for ps analysis stamps that uses spatial correlation of interferogram phase to find pixels with low phase variance in all terrains with or without buildings prior knowledge of temporal variations in the deformation rate is not required for their identification we apply stamps to volcan alcedo where conventional insar fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time we detect two sources of deformation the first we model as a contracting pipe like body which we interpret to be a crystallizing magma chamber the second is downward and lateral motion on the inner slopes of the caldera which we interpret as landsliding

unsaturated hydraulic conductivity in limestone dolines influence of vegetation and rock fragments abstract vegetation and rock fragments have a profound impact on runoff generation in the dolines of the sierra de gador southeastern spain this study investigated the effect of vegetation and rock fragments on unsaturated hydraulic conductivity k h in three limestone dolines and examined whether variation in k h was consistent with differences in runoff from simulated rainfall tension infiltrometers were used to measure unsaturated hydraulic conductivity at three pressure heads h of 30 60 and 120 mm at 70 locations within the three dolines generally the trends of the k h were consistent with the simulated rainfall data and accounted for difference in runoff for the vegetated surfaces vegetation resulted in high infiltration with unsaturated hydraulic conductivities at 30 and 60 mm are significantly greater for the vegetated surface than for the rock fragment covered surface and bare soil surface rock fragments had no obvious effect on soil hydraulic conductivity as compared with bare soils the k h of the non crusted soil were 2 5 times higher than that of the crusted soil the k h decreased with increasing tensions k 60 and k 120 were only 8 4 and 0 89 respectively of k 30 for the vegetated surfaces and were about 30 and 8 7 respectively of k 30 for both rock fragment covered surfaces and bare soils suggesting that pores in the 0 5 to 1 mm diameter range dominate flow under unsaturated conditions there were significant differences in k h among the different topographic units of the dolines and k h tended to be higher in the upper position than in the lower position of the doline

sensitivity analysis of eurosem using monte carlo simulation ii the effect of rills and rock fragments a sensitivity analysis of the surface and catchment characteristics in the european soil erosion model eurosem was carried out with special emphasis on rills and rock fragment cover the analysis focused on the use of monte carlo simulation but was supplemented by a simple sensitivity analysis where input variables were increased and decreased by 10 the study showed that rock fragments have a significant effect upon the static output parameters of total runoff peak flow rate total soil loss and peak sediment discharge but with a high coefficient of variation the same applied to the average hydrographs and sedigraphs although the peak of the graphs was associated with a low coefficient of variation on average however the model was able to simulate the effect of rock fragment cover quite well the sensitivity analysis through the monte carlo simulation showed that the model is particularly sensitive to changes in parameters describing rills and the length of the plane when no rock fragments are simulated but that the model also is sensitive to changes in the fraction of non erodible material and interrill slope when rock fragments were embedded in the topsoil for rock fragments resting on the surface changes in parameter values did not affect model output significantly the simple sensitivity analysis supported the findings from the monte carlo simulation and illustrates the importance when choosing input parameters to describe both rills and rock fragment cover when modelling with eurosem

impact of subsurface rock fragments on runoff and interrill soil loss from cultivated soils field and laboratory studies have indicated that rock fragments in the topsoil may have a large impact on soil properties soil quality hydraulic hydrological and erosion processes in most studies the investigated rock fragments still remain visible at the soil surface and only properties of these visible rock fragments are used for predicting runoff and soil loss however there are indications that rock fragments completely incorporated in the topsoil could also significantly influence the percolation and water distribution in stony soils and therefore also infiltration runoff and soil loss rates therefore in this study interrill laboratory experiments with simulated rainfall during 60 min were conducted to assess the influence of subsurface rock fragments incorporated in a disturbed silt loam soil at different depths below the soil surface i e 0 001 0 01 0 05 and 0 10 m on infiltration surface runoff and interrill erosion processes for small and large rock fragment sizes i e mean largest diameter equals 0 04 and 0 20 m respectively although only small differences in infiltration rate and runoff volume are observed between the soil without rock fragments control and the one with subsurface rock fragments considerable differences in total interrill soil loss are observed between the control treatment and both contrasting rock fragments sizes this is explained by a rapid increase in soil moisture in the areas above the rock fragments and

velocity probability density functions from altimetry probability density functions pdfs are employed to evaluate the distribution of velocities in the global ocean this study computes pdfs of ocean surface velocity using altimetric data from the topex poseidon satellite results show that the shape of the observed pdfs changes with the size of the domain over which they are calculated if data are drawn from a small region of the ocean the pdfs are gaussian as the area of the ocean considered increases the pdfs take on more exponential shapes the appearance of exponential pdfs is particularly pronounced when data are drawn from a large range of latitudes while data drawn from constant latitude tend to have a more gaussian pdf the authors show that this distinction between zonal and meridional regions is also observed in acoustic doppler current profiler measurements the authors propose a simple statistical model to explain the observed velocity pdfs this explanation depends on the fact that root mean squared velocity or the width of velocity pdf varies throughout the ocean the velocity pdf is predicted from the distribution of the mean squared velocity the model matches the observations in predicting a pdf that is parabolic for small velocities with generalized exponential decay for large velocities

resolving marine gravity with ers 1 satellite altimetry to estimate how well ers 1 data from the 35 day repeat mission can resolve fine structure in the marine geoid or gravity field we compare along track gravity and gridded gravity fields derived from ers 1 fast delivery altimeter data to those computed from geosat geodetic mission altimeter observations in the southern ocean we find that single passes of ers 1 data can resolve along track gravity anomalies with wavelengths as short as 28 30 km i e comparable to geosat however the ers 1 gridded gravity field can only resolve anomalies as short as 66 km versus 18 km for geosat this two dimensional resolution is limited by the larger ground track spacing 35 km at 60 s of ers 1 to resolve fine structure in the marine gravity field it is essential to have altimeter data along more closely spaced ground tracks such as those planned for the ers 1 176 day repeat mission in 1994

erosion extension of indurated volcanic soils of mexico by aerial photographs and remote sensing analysis in the northern part of michoacan state in mexico between the patzcuaro and cuitzeo lakes we used aerial photographs and spot satellite data to define the spatial and temporal extensions of soil erosion over indurated volcanic material called tepetates segmentation techniques combined with graphic mask were applied over the aerial photographs in order to obtain the extension of eroded areas for 1975 1995 and 2000 an unsupervised classification was performed over various band combinations of spot the eroded areas were checked and improved with ground control points the results show that there are no more eroded areas today than 25 years ago there is however an evolution of the eroded areas some of them have disappeared while others have become larger a change in land use intensity explains the regression of eroded area in the north and the augmentation of eroded surfaces in the south the result obtained with spot imagery classification allows discrimination of four different erosion degrees where only one could be distinguish with aerial photographs however it is not possible to distinguish outcropping tepetates and outcropping andesit with spot as well additional socioeconomic studies and studies over spectral signatures of eroded materials in relation with their mineral contents are in process

comparison of hydrodynamic parameters for predicting soil and water loss on simulation landslide deposit slope in wenchuan earthquake area china hydrodynamic parameters should be identified firstly for predicting soil and water loss with specific issues and objectives the laboratory simulation scouring experiments were conducted with different gravel contents flow discharges and slopes based on the field investigation which achieved the most suitable parameter for predicting soil and water loss on simulation landslide deposit slope in wenchuan earthquake area china the results showed that the gravel content of 25 always was the threshold that controlled the flow shear stress and stream power increased or decreased under different flow discharges the unit stream power up and unit flow energy e both decreased when gravel contents increased the ratio of manning coefficient to flow depth n h was higher in fine sediments with gravels than that without gravels the flow discharge had the consistent effects on hydrodynamics which was ordered as 4 8 12 l min 1 the was the most suitable parameter for predicting soil and water loss by considering the degree of reliability even though the also had significant positive power function with soil and water loss the n h could describe the hydrodynamics and soil and water loss and be the alternative parameter for predicting soil and water loss the results provide useful information for soil and water loss prediction in landslide deposits

surface crusting in two alluvial soils of northen niger valentin c 1991 surface crusting in two alluvial soils of northen niger geoderma 48 201 222 surface crusting was studied in a sandy soil and a clay loam soil in northern niger in a subdesert to desert environment light microscopy electron microscopy image analysis and soil physics were used to study and explain different crusting processes in experimental plots two 1 m2 plots on each soil were subjected to rainfall simulation in the field under natural and tilled surface conditions this study demonstrates that kinetic energy of rainfall is the major crusting factor for the sandy soil waterlogging and subsequent slaking led to the formation of structural and depositional crusts in the tilled clay loam plot in this case a surface crust can be formed regardless of kinetic energy of the rainfall this was substantiated through double ring infiltrometer measurements in both soils infiltration was severely hindered by crusting the relationships of crusting to water and wind erosion were more ambiguous four types of crusts could be defined from this study in terms of structure genetic processes and properties it could also be demonstrated that crust control practices should take into account the texture of the original soil materials

runoff and sediment yield from topsoils with different porosity as affected by rock fragment cover and position abstract interrill runoff and sediment yield from a topsoil having essentially textural pores and from another with structural pores were measured in the laboratory under simulated rain to investigate the effects of cover and positions of rock fragments the results reveal that the relation between the cover of rock fragments and interrill runoff or sediment yield can be negative as well as positive porosity in the soil near rock fragments determines both the type of relation and the degree to which the positions of rock fragments affect this relation rock fragments increase runoff and sediment yield when well embedded in a surface seal i e a top layer with essentially textural pore spaces a negative relation occurs either where rock fragments are partly embedded in a top layer with structural porosity or where the rock fragments rest on the surface of a soil having either textural or structural pore spaces the time at which macropores at the soil surface close is crucial for then the effect of the cover of rock fragments on the generation of runoff switches from reduction to an increase since cover can have an ambivalent effect on the hydrological and erosion response descriptions of topsoils containing rock fragments should include the type of soil porosity as well as the positions of rock fragments

stacked global satellite gravity profiles gravity field recovery from satellite altimetry provides global marine coverage but lacks the accuracy and resolution needed for many exploration geophysics studies the repeating ground tracks of the ers 1 2 geosat and topex poseidon altimeters offer the possibility of improving the accuracy and resolution of gravity anomalies along widely spaced 40 km spacing tracks however complete ocean coverage is usually needed to convert the sea surface height or along track slope measurements into gravity anomalies here we develop and test a method for constructing stacked gravity profiles by using a published global gravity grid sandwell and smith 1997 v7 2 as a reference model for the slope to gravity anomaly conversion the method is applied to stacks averages of geosat erm up to 62 cycles ers 1 2 up to 43 cycles and topex up to 142 cycles satellite altimeter profiles we assess the accuracies of the ers 1 2 profiles through a comparison with a gravity model of the northern gulf of mexi

effects of soil surface components on soil hydrological behaviour in a dry mediterranean environment southern spain abstract various researchers have studied the spatial pattern of soil surface components such as vegetation rock fragments bare soil litter and surface crusts as a key factor of hydrological behaviour in mediterranean settings with heterogeneous patches of vegetation cover and strong human impact the studies indicate that there is a mosaic of patches that generate run off or infiltrate overland flow distributed in various ways along hillslopes few of these studies however have looked at areas underlain by metamorphic rocks such as phyllites or schists this study analysed the temporal and spatial variability of the effects of soil surface components on hydrological processes in a small dry mediterranean catchment underlain by metamorphic rocks a systematic sampling of multiple sites throughout a hydrological year was carried out we related the hydrological behaviour of soil surface components to 1 their position along the hillslope 2 the distance of existing vegetation tussocks from the line of run off 3 rainfall intensity and 4 the main physical chemical soil properties affecting infiltration processes statistical analysis was used to check the validity of the relationships the results show that soil surface components have highly variable effects in both space and time on soil hydrological behaviour these effects particularly depend on the location along the line of maximum slope and the intensity of preceding rainfall whose interaction defines soil hydrological status these results are similar to those for other mediterranean settings with different lithology in that the succession of contributing patches are hydrologically interconnected along a hillslope the variables used and the grouping of explanatory variables through principal component analyses were found to be suitable for discussing the spatial distribution of soil surface components in the hydrologically dynamic environment of the study area

empirical relations for the sediment transport capacity of interrill flow experiments were carried out in order to measure the sediment transport capacity of interrill flow with and without rainfall and to relate the transport capacity to selected hydraulic parameters such as effective stream power and shear velocity different sediments were used in order to study the effect of grain size the proposed relationships show considerable variations with grain size and there is only a minor effect of rainfall on the transport capacity which also seems to be grain size dependent the proposed relationships can be used to predict sediment transport capacity of interrill flow and can therefore contribute to the development of physically based erosion models

seafloor tectonic fabric from satellite altimetry abstract ocean floor structures with horizontal scales of 10 to a few hundred kilometers and vertical scales of 100 m or more generate sea surface gravity anomalies observable with satellite altimetry prior to 1990 altimeter data resolved only tectonic lineaments some seamounts and some aspects of mid ocean ridge structure new altimeter data available since mid 1995 resolve 10 km scale structures over nearly all the world s oceans these data are the basis of new global bathymetric maps and have been interpreted as exhibiting complexities in the sea floor spreading process including ridge jumps propagating rifts and variations in magma supply this chapter reviews the satellite altimetry technique and its resolution of tectonic structures gives examples of intriguing tectonic phenomena and shows that structures as small as abyssal hills are partially resolved a new result obtained here is that the amplitude of the fine scale 10 80 km roughness of old ocean floor is spreading rate dependent i

resolution of the scripps noaa marine gravity field from satellite altimetry the july 1995 declassification of the entire geosat gm satellite altimeter data set enabled a joint scripps noaa effort to compute a new version 7 2 marine gravity field on a 2 minute grid this gravity field covers the world oceans between 72 n and 72 s and is derived from a combination of ers 1 and geosat gm and erm data an earlier noaa geosat only gravity field solution was confined to the southern latitudes because the 1992 declassification was limited to gm data south of 30 s a simple coherence analysis between accurately navigated ship gravity profiles and comparable gravity profiles obtained from the gravity grids reveals that the scripps noaa gravity field is coherent with ship gravity down to 23 30 km this slight increase in resolution over the previous noaa geosat only gravity field short wavelength resolution of 26 30 km implies that the increased spatial coverage provided by the ers i altimeter when combined with geosat improves the solution coherence analyses between satellite gravity and ship topography and ship gravity and ship topography show that even shorter wavelength gravity anomalies 13 km are present in sea surface measurements made by ship even so the scripps noaa marine gravity field does an excellent job of resolving most of the short wavelength gravity anomalies covering the world oceans

soil hydraulic properties on the steep karst hillslopes in northwest guangxi china soil hydraulic properties such as soil infiltration rate and hydraulic conductivity are closely linked to runoff generation and infiltration processes but little is known about them on karst hillslopes the objectives of this paper were to investigate the change in soil stable infiltration rate q s and near saturated hydraulic conductivity k ns in different slope positions and to understand their relationship with rock fragment content and soil texture within the topsoil in subtropical karst regions of southwest china tension infiltrometers 20 cm in diameter were used to measure q s and k ns at pressure head of 20 mm on hillslopes 1 a disintegrated landslide failure and 2 an avalanche slope the change of q s and k ns was great and they mostly had a moderate variability with coefficient of variations cv between 0 1 and 1 0 in the different slope positions on average q s ranged from 0 43 to 4 25 mm min and k ns varied from 0 75 to 11 00 mm min these rates exceed those of most natural rainfall events confirming that overland flow is rare on karst hillslopes from bottom to top q s and k ns had a decrease increase decrease trend due to the presence of large rock outcrops 2 m in height on hillslope 1 but had an increasing trend on hillslope 2 with less complex landform they tended to increase with increase in total rock fragment content 5 250 mm within the topsoil as well as slope gradient on both hillslopes pearson correlation analysis suggested that higher coarse pebble 20 75 mm cobble 75 250 mm and sand 2 0 05 mm contents as well as total rock fragment content could significantly facilitate water infiltration into soils but higher clay 0 002 mm content could restrict water movement this result indicated that rock fragment sand and clay contents may remarkably affect water flow in the topsoil layers and should be considered in hydrological modeling on karst hillslopes in subtropical regions

detection of coastlines in sar images using wavelet methods to monitor map and model sediment transport in big river estuaries complete maps of bottom topography are needed this information is obtained by extracting shorelines from synthetic aperture radar sar images of the european remote sensing satellites ers 1r tide gauge information and heights from a dynamic tide model the aim of this paper is to show how coastlines can be derived from sar images by using wavelet and active contour methods in a first step an edge detection method suggested by mallat et al 1992 is applied to ers sar images to detect all edges above a certain threshold a blocktracing algorithm ba then determines the boundary area between land and water a refinement is achieved by local edge selection in this coastal area and by propagation along the wavelet scales in a final step the refined edge segments are joined by an active contour algorithm a model solution for land water segmentation is constructed from a sar image by visual inspection the error is estimated by comparing the results from the algorithms to this model solution the area under investigation is the elbe estuary which is located in the intertidal zone of the german bight due to high rates of sediment transport in this area local government agencies have to spend large amounts of money to keep shipping lanes open the demonstrated method is shown to be suitable for operational use by applying it to a data set of 24 sar images covering a time span of approximately five years

analysis of soil surface component patterns affecting runoff generation an example of methods applied to mediterranean hillslopes in alicante spain abstract spatial patterns of soil surface components vegetation rock fragments crusts bedrock outcrops etc are a key factor determining hydrological functioning of hillslopes a methodological approach to analyse the patterns of soil surface components at a detailed scale is proposed in this paper the methods proposed are applied to two contrasting semi arid mediterranean hillslopes and the influence of soil surface component patterns on the runoff response of the slopes was analysed a soil surface components map was derived from a high resolution photo mosaic obtained in the field by means of a digital camera rainfall simulation experimental data were used to characterise the hydrological behaviour of areas with a specific pattern of soil surface components by means of the parameters of the horton equation plot runoff data were extrapolated at the hillslope scale based on the soil surface component maps and their hydrological characterisation the results show that in both slopes runoff generation is concentrated up and downslope with a water accepting area in the centre of both slopes disrupting the hydrological connectivity at the slope scale this reinfiltration patch at the centre of the slope is related to the type of soil surface component and its spatial pattern herbaceous vegetation and on top rock fragments increase the infiltration capacity of soils at the centre of the slope in contrast embedded rock fragments rock outcrops as well as crusted surfaces located in the upper and lower slopes favour runoff generation in these areas in addition a general pattern of water contribution areas downslope is apparent on both slopes the south facing slope shows a higher hydrological connectivity and more runoff 55 of the surface of the south facing slope produces runoff at the end of a 1 hour rainfall event and 17 3 of the surface is covered by a runoff depth between 0 5 and 1 mm while on the north facing slope only 38 of the surface produces runoff under the same conditions longitudinal connectivity of runoff is higher at the south facing slope where more runoff generating surfaces appear and where the vegetation pattern favours the connectivity of bare areas

discharge and suspended sediment patterns in a small mountainous watershed with widely distributed rock fragments summary understanding and quantifying sediment loads is important in watersheds with highly erodible materials which will eventually cause environmental and ecological problems within this context suspended sediment ss transport and its temporal dynamics were studied in a small mountainous watershed with sloping lands containing rock fragments in subtropical china soils containing rock fragments with many macro pores have a high permeability rate over a 7 year period the mean runoff coefficient of this watershed was 0 65 overall 30 flood events were monitored and accounted for 95 5 27 3 17 1 of the total ss load precipitation and total discharge respectively over a 5 year period the presence of rock fragments in soils can affect soil loss when comparing the soil loss in the studied watershed with that of other watersheds under similar climatic conditions rock fragments negatively affect soil loss however an extreme event occurred on 14 august 1990 and the sediment load exhibited a phenomenon called small deposits towards lump withdrawal which resulted in a soil loss of 20 499 t 4 6 times the mean yearly soil loss this event exhausted most of the ss s stored by the rock fragments on the slope and channel following this event the mean ss concentration ssc of the 11 events was 1 05 kg m 3 and the mean ssc of the 18 previous events was 1 75 kg m 3 twelve variables were separated using the classical hydrograph separation method partial least squares regression plsr was used to determine the highly co related variables of the discharge the results indicated that plsr could explain runoff well the relationship between discharge and ssc was highly scattered during 24 flood events three types of hysteresis loops were observed clockwise 17 events figure eight 3 events and complex 4 events

antarctic marine gravity field from high density satellite altimetry summary closely spaced satellite altimeter profiles 5 km collected during the geosat geodetic mission geosat gm and those planned for the extended ers 1 mission are easily converted to grids of vertical gravity gradient and gravity anomaly as profile spacing decreases it becomes increasingly difficult to perform a crossover adjustment on the original geoid height profiles without introducing large cross track gradients if one is only interested in the horizontal and vertical derivatives of the gravitational potential however adjustment of the profile is unnecessary the long wavelength radial orbit error is suppressed well below the noise level of the altimeter by simply taking the along track derivative of each profile ascending and descending slope profiles are then interpolated onto separate uniform grids these two grids are summed and differenced to form comparable grids of east and north vertical deflection using laplace s equation the vertical gravity gradient is calculated directly from the vertical deflection grids fourier analysis is required to construct gravity anomalies from the two vertical deflection grids these techniques are applied to high density 2 km profile spacing geosat gm profiles in antarctic waters 60 s to 72 s gridding and interpolation are performed using the method of projection onto convex sets where the smoothness criteria corresponds to upward continuation through 4 km of ocean the resultant gravity grids have resolution and accuracy comparable to shipboard gravity profiles after adjustment of a dc shift in the shipboard gravity profiles 5 mgal the rms difference between the ship and satellite gravity is 5 5 mgal many interesting and previously uncharted features are apparent in these new gravity maps including a propagating rift wake and a large leaky transform along the pacific antarctic rise

mechanisms governing incipient motion of ellipsoidal rock fragments in concentrated overland flow a modified shields criterion for incipient motion of ellipsoidal rock fragments in concentrated overland flow was previously defined based on laboratory data in order to apply this new criterion an estimate of the angle of repose for the considered rock fragment is needed therefore a set of laboratory experiments was conducted in order to develop an algorithm for this estimation the main result of these experiments shows that each rock fragment lying on a rill bed of a given roughness is characterized by a normally distributed set of angles of repose this distribution reflects the different local slopes that a rock fragment can experience the new criterion has been successfully validated for single rock fragments lying on an erodible rill bed application of this criterion to field conditions however did not explain all variation in the observed data in fact rock fragments having sizes larger than the predicted flow competence were removed during a moderate rainfall event a consideration of several mechanisms reveals that collisions between rock fragments seems likely to be a significant mechanism explaining the observed discrepancy

effects of rock fragment size and cover on overland flow hydraulics local turbulence and sediment yield on an erodible soil surface the interactions between overland flow hydraulics and sediment yield were studied in flume experiments on erodible soil surfaces covered by rock fragments the high erodibility of a non cohesive fine sediment d50 0 09mm permitted the effects of local turbulence and scour on sediment yield to be examined overland flow hydraulics and sediment yield were compared for experiments with pebble d50 1 5cm and cobble d50 8 6cm rock fragment covers cover percentages range from 0 to 99 per cent rock fragment size strongly affects the relations between flow hydraulics and rock fragment cover for pebbles spatially averaged hydraulic parameters flow velocity flow depth effective flow width unit discharge total shear stress darcy weisbach friction factor percentage grain friction and grain shear stress vary most rapidly within cover percentages at low covers power functions in contrast for cobbles these parameters vary most rapidly within cover percentages at high covers exponential functions as the type of the function that describes the relation between flow hydraulics and cover percentage can be deduced from the ratio of rock fragment height to flow depth the continuity equation can be employed to determine the actual coefficients of the functions provided the regression of one hydraulic parameter e g flow velocity with cover percentage is known and a good estimate exists for two values of another hydraulic variable for a low and a high cover percentage the variation of sediment yield with cover percentage is also strongly dependent on rock fragment size but neither the convex upward relation for pebbles nor the positive relation for cobbles can be solely attributed to the spatially averaged hydraulics of sheet flow rock fragments induce local turbulence that leads to scour hole development on the stoss side of the rock fragments while deposition commonly occurs in the wake this local scour and deposition substantially affects sediment yield however scour dimensions cannot be predicted by spatially averaged flow hydraulics an adjustment of existing scour formulas that predict scour around bridge piers is suggested sediment yield from non cohesive soils might then be estimated by a combination of sediment transport and scour formulas

a runoff capability classification system based on surface features criteria in semi arid areas of west africa abstract an analysis of the factors influencing infiltration and runoff was carried out using data obtained under simulated rainfall conditions on 87 plots in arid and semi arid areas of west africa arranged in a hierarchical sequence one of the key factors to emerge from this typological classification is the type of surface crust together with faunal activity vegetation cover and surface roughness this parameter permits the inclusion of a unit surface factor in the classification system each unit surface is characterized in terms of genetic morphological and hydrological properties at a higher level the combination of these unit surfaces allows a soil surface features unit to be defined based on an original mapping method the samples once defined in this system were found to correspond to homogeneous criteria both in terms of evolution dynamics and hydrological behaviour furthermore such cartography could be successfully extrapolated through remote sensing image analysis making possible a classification of the runoff capability of small watersheds based on objective and standardized criteria

phase gradient approach to stacking interferograms the phase gradient approach is used to construct averages and differences of interferograms without phase unwrapping our objectives for change detection are to increase fringe clarity and decrease errors due to tropospheric and ionospheric delay by averaging many interferograms the standard approach requires phase unwrapping scaling the phase according to the ratio of the perpendicular baseline and finally forming the average or difference however unique phase unwrapping is usually not possible since the phase gradient due to topography is proportional to the perpendicular baseline phase unwrapping is unnecessary prior to averaging or differencing phase unwrapping may be needed to interpret the results but it is delayed until all of the largest topographic signals are removed we demonstrate the method by averaging and differencing six interferograms having a suite of perpendicular baselines ranging from 18 to 406 m cross spectral analysis of the difference between two tandem interferograms provides estimates of spatial resolution which are used to design prestack filters a wide range of perpendicular baselines provides the best topographic recovery in terms of accuracy and coverage outside of mountainous areas the topography has a relative accuracy of better than 2 m residual interferograms single interferogram minus stack have tilts across the unwrapped phase that are typically 50 mm in both range and azimuth reflecting both orbit error and atmospheric delay smaller scale waves with amplitudes of 15 mm are interpreted as atmospheric lee waves a few global positioning system gps control points within a frame could increase the precision to 20 mm for a single interferogram further improvements may be achieved by stacking residual interferograms

rainwash experiments on the erodibility of loose sediments laboratory experiments using simulated rainfall splash boards and trays were conducted in order to obtain information on the erodibility of loose sediments as a time dependent phenomenon in all ten different sediments ranging from silt d50 24 m to coarse sand d50 593 m were studied the effect of three different initial states of the sediments namely the air dry state t1 the field capacity state t2 and the desiccated state t3 on the erodibility was also assessed variations in detachability during a rain erosion experiment can be explained by change in water content including liquefaction and the development of a water layer on the surface cohesion and granulometric composition of the top layer the coarsest sandy sediments almost always yielded the highest detachability when starting from an initial field capacity state t2 for the finer sediments the highest detachability was found for the homogeneous and not yet compacted initial air dry state t1 the effect of the initial desiccated state t3 on the detachability of the finer sediments was also a function of the rainfall duration the relationship between detachability and median grain size of the sediments was very similar to the relation between grain size and the susceptibility to runoff and wind erosion established by other investigators the highest detachability was found for a fine very well sorted sand with a median grain size of 96 m

relation between infiltration and stone cover on a semiarid hillslope southern arizona abstract a knowledge of the spatial distribution of infiltration rates is essential to the application of realistic distributed rainfall runoff models in semiarid areas one method of determining this distribution is to develop a predictive equation based on a readily observable surface property such as stone cover previous studies of the relation between infiltration and stone cover on shrub covered semiarid hillslopes have yielded both positive and negative correlations it is suggested that positive correlations result where infiltration measurements are confined to areas between large shrubs negative correlations on the other hand reflect pronounced shrub intershrub differences in infiltration and stone cover and are found where both shrub and intershrub areas are sampled in this study of a semiarid hillslope in southern arizona both shrub and intershrub areas are sampled and a negative correlation is obtained between infiltration and stone cover this correlation arises from the fact that under shrubs fine sediments have accumulated primarily as a result of differential splash whereas between shrubs such sediments have been selectively removed by a combination of rainsplash and overland flow leaving behind a gravel lag consequently infiltration rates are higher under shrubs than between them owing to the higher percentage of sand in the surface soil the larger quantity of organic matter both within the soil and on its surface and the greater digging and burrowing by animals in addition simulated rainfall experiments imply that shrubs with moderately dense canopies are more effective than adjacent surface gravels in dissipating the kinetic energy of raindrops and thereby reducing surface sealing and promoting infiltration inasmuch as the field site is typical of gentle shrub covered piedmont hillslopes over much of the sonoran desert inverse relations between infiltration rate and stone cover are probably characteristic of such hillslopes and may be used to predict the spatial distribution of infiltration rates for inclusion in rainfall runoff models

multitemporal backscattering logistic analysis for intertidal bathymetry a new methodology for the mapping of intertidal terrain morphology is presented it is based on the use of synthetic aperture radar sar images and the temporal correlation between the sar backscatter intensity and the water level on the intertidal zone the proposed methodology does not require manual editing providing a set of geolocated pixels that can be used to generate a digital elevation model of the intertidal zone the methodology is validated using terrasar x sar images acquired over tagus estuary this methodology can be useful for the regular updating of intertidal bathymetric models useful for both flood hazard mitigation and morphodynamics modeling

rocking the landscape chacma baboons papio ursinus as zoogeomorphic agents abstract animals sculpt landforms by physically altering the substrate many digging and burrowing animals are then considered zoogeomorphic agents while the significance of soil disturbing species is well established geomorphic impacts are rarely quantified for rock transporting species the chacma baboon papio ursinus a widespread and abundant primate throughout most of southern africa south of the zambezi may be a zoogeomorphic agent through its role in rock displacement while foraging we quantified baboon rock movement along belt transects placed across a catena in a semi arid karoo environment in south africa along each transect we the counted the number of moved rocks and recorded their dimensions mass and shape and related this to rock i e mass shape and landscape i e hillslope obstacles that hinder movement features to assess the drivers of the extent of rock transport baboon rock movement was found to be extensive ranging from 26 to 54 615 kg 10 967 2 2300 9 kg of rock material displaced per ha and year the distance of rock movement was influenced by rock size large rocks were displaced further and rock shape flat rocks were moved further followed by angular and rounded rocks furthermore slope influenced rock movement with rocks displaced greater distances on steeper slopes baboon rock movement brought about a loss in potential energy and a change in landscape entropy through the net downward movement of rocks we show that baboons play an important geomorphic role and probably serve as a keystone species as they are the only species in this environment to intentionally move rocks in this way because baboons are considered pests and are widely persecuted their role in zoogeomorphic processes are vulnerable to being lost

mapping the nonstationary internal tide with satellite altimetry temporal variability of the internal tide has been inferred from the 23 year long combined records of the topex poseidon jason 1 and jason 2 satellite altimeters by combining harmonic analysis with an analysis of along track wavenumber spectra of sea surface height ssh conventional harmonic analysis is first applied to estimate and remove the stationary components of the tide at each point along the reference ground tracks the wavenumber spectrum of the residual ssh is then computed and the variance in a neighborhood around the wavenumber of the mode 1 baroclinic m2 tide is interpreted as the sum of noise broadband nontidal processes and the nonstationary tide at many sites a bump in the spectrum associated with the internal tide is noted and an empirical model for the noise and nontidal processes is used to estimate the nonstationary semidiurnal tidal variance the results indicate a spatially inhomogeneous pattern of tidal variability nonstationary tides are larger than stationary tides throughout much of the equatorial pacific and indian oceans

erosion in mediterranean landscapes changes and future challenges abstract intense erosion processes are widespread in the mediterranean region and include sheet wash erosion rilling gullying shallow landsliding and the development of large and active badlands in both subhumid and semi arid areas this review analyses the main environmental and human features related to soil erosion processes and the main factors that explain the extreme variability of factors influencing soil erosion particularly recent land use changes the importance of erosion in the mediterranean is related to the long history of human activity in a region characterized by low levels of annual precipitation the occurrence of intense rainstorms and long lasting droughts high evapotranspiration the presence of steep slopes and the occurrence of recent tectonic activity together with the recurrent use of fire overgrazing and farming these factors have resulted in a complex landscape in which intensification and abandonment wealth and poverty can co exist the changing conditions of national and international markets and the evolution of population pressure are now the main drivers explaining land use changes including farmland abandonment in mountain areas the expansion of some subsidized crops to marginal lands and the development of new terraces affected by landslides and intense soil erosion during extreme rainstorm events the occurrence of human related forest fires affecting thousands of hectares each year is a significant problem in both the northern and southern areas of the mediterranean basin here we highlight the rise of new scientific challenges in controlling the negative consequences of soil erosion in the mediterranean region 1 to reduce the effects and extent of forest fires and restructure the spatial organization of abandoned landscapes 2 to provide guidance for making the eu agricultural policy more adapted to the complexity and fragility of mediterranean environments 3 to develop field methods and models to improve the identification of runoff and sediment contributing areas 4 to contribute to the conservation of landscapes i e bench terraced fields having high cultural and productivity values 5 to improve knowledge of the hydrological and geomorphological functioning of badlands with the aim of reducing sediment yield and accessibility 6 to better understand the effect of climate change on soil erosion in the mediterranean region and 7 to improve quantitative information on long term soil erosion

topographic mapping of the german tidal flats analyzing sar images with the waterline method the waterline method is used to derive the topography of the tidal flats along the german coast by evaluation of synthetic aperture radar sar images a series of about 70 european remote sensing satellites sar images of the german bight taken at different water levels within four years is analyzed to detect the borderline between tidal flats and adjacent water areas using a wavelet based edge detection algorithm after geocoding the waterlines are combined with the corresponding water levels to represent the topography on an irregularly spaced grid the water levels are taken from a numerical tide model and corrected with the measured gauge data interpolation of these data into a regular grid yields a topographic map of the intertidal zone while the general practicability of this method has been demonstrated in previous studies for smaller test areas this paper is the first attempt to generate maps of a large area on a yearly basis

prediction of sediment thickness in the norwegian greenland sea from gravity inversion 1 we explore the feasibility of inverting freely available altimetry derived gravity grids for sediment thickness on oceanic crust a four layer earth model is adopted assuming that the gravity signal from the base of the sedimentary layer can be fully isolated from the observed free air gravity the following additional data are required 1 shipboard bathymetry for reliable bouguer correction 2 oceanic crustal ages to correct for gravity anomalies related to the thermal history of lithospheric breakup and seafloor spreading and 3 some wide angle seismic observations of sediment thickness a fixed relationship between the base of the sedimentary layer and the moho is also required because of limited gravity resolution at large depths the final inversion setup searches for three control parameter values density of uppermost sediments density of oceanic crystalline crust and thermal diffusivity of mantle rock that minimize misfit between the earth model and observations applied to the norwegian greenland sea the inversion successfully predicts locations of 20 25 km wide depocenters and crystalline crustal highs yet 1 km thickness errors are common even in well constrained areas the largest errors are associated with underplated crust active mid ocean ridges and the continent ocean boundary indicating locally incorrect assumptions of mantle thermal structure and crystalline crustal thickness the thicknesses of 4 km thick submarine fans are underpredicted probably because of too low sedimentary densities in the earth model if these limitations are acceptable or do not apply because of simple crustal structure gravity inversion may be used for mapping regional sedimentary patterns e g in the arctic ocean

high accuracy high resolution gravity profiles from 2 years of the geosat exact repeat mission satellite altimeter data from the first 44 repeat cycles 2 years of the geosat exact repeat mission geosat erm were averaged to improve accuracy resolution and coverage of the marine gravity field individual 17 day repeat cycles two points per second were first edited and differentiated resulting in alongtrack vertical deflection i e alongtrack gravity disturbance to increase the signal to noise ratio 44 of these cycles were then averaged to form a single highly accurate vertical deflection profile the largest contributions to the vertical deflection error is short wavelength altimeter noise and longer wavelength oceanographic variability the combined noise level is typically 6 rad both types of noise are reduced by averaging many repeat cycles over most ocean areas the uncertainly of the average profile is less than 1 rad 0 206 arcsec which corresponds to 1 mgal of alongtrack gravity disturbance however in areas of seasonal ice coverage its uncertainty can exceed 5 rad to assess the resolution of individual and average geosat gravity profiles the cross spectral analysis technique was applied to repeat profiles individual geosat repeat cycles are coherent 0 5 for wavelengths greater than about 30 km and become increasingly incoherent at shorter wavelengths this emit of resolution is governed by the signal to noise ratio thus when many geosat repeat profiles are averaged together the resolution limit typically improves to about 20 km except in shallow water areas further improvements in resolution will be increasingly difficult to achieve because the short wavelength components are attenuated by upward continuation from the seafloor to the sea surface these results suggest that the marine gravity field can be completely mapped to an accuracy of 2 mgal and a half wavelength resolution of 12 km by a 4 5 year satellite altimeter mapping mission

rock fragments in top soils significance and processes this introductory paper reviews various aspects of rock fragments in top soils such information is required for various reasons and in particular for predicting the impact of climatic or landuse changes on the response of these soils particular attention is paid to the definition and measurement of rock fragment content in top soils the density of soils containing rock fragments the spatial distribution and movement of rock fragments in top soils the effects of rock fragments on some key hydrological processes thermal properties of top soils physical soil degradation soil erosion and soil productivity

soil thickness effect on hydrological and erosion characteristics under sloping lands a hydropedological perspective abstract soil thickness exerts a first order control on the hydrological processes of the hillslopes however from a hydropedological perspective the knowledge of soil thickness effect on hydrological and erosion characteristics under sloping lands is limited based on a comprehensive survey of an experimental watershed in the three gorges area of china five typical sloping land plots 2 m 1 m with different soil thickness were selected along a hillslope to investigate their hydrological processes and erosion response under three rainfall intensities 60 90 and 120 mm h 1 using a portable rainfall simulator the results can be summarized as follows 1 the surface flow coefficient was increased with increasing soil thickness especially under the event of 60 mm h 1 2 the subsurface flow of the 23 31 and 45 cm plots mainly took the form of preferential flow conversely the 59 and 76 cm plots mainly took the form of matrix flow 3 a prolonged low intensity rainfall is much more likely to facilitate deep percolation and subsurface flow than a short high intensity rainfall regardless of soil thickness 4 soil thickness and rock fragment cover were the most important factors than other soil properties in determining the hydrological and erosion behaviors thin soils showed higher infiltration capacity than thick soils due to their more distinct hydrological processes of subsurface flow and deep percolation rock fragment cover enhanced infiltration and served as a shield to protect the soil surface from detaching due to the synergies between thin soil thickness and high rock fragment cover thin soils displayed significantly lower erosion rates than thick soils in all rainfall events which increased from 211 g m 2 h 1 for the 23 cm plot with rainfall of 60 mm h 1 to 4220 g m 2 h 1 for the 76 cm plot with rainfall of 120 mm h 1 our study suggested that the emerging interdisciplinary field of hydropedology promotes synergistic integration of pedology e g watershed scale soil thickness investigation and soil profile description and hydrology e g rainfall simulation subsurface flow and deep percolation to enhance the holistic study of soil water interactions in the sloping lands with different soil thickness

characteristics of stone covers on the surface of basalt flows in arid northeast jordan variations in the stone covers on desert surfaces have implications for the operation of hydrological processes some recent attention has been given to the difficulties of identifying and quantifying relevant characteristics of stone covers investigation of how such characteristics vary in relation to geological and topographical controls are limited results are presented of a field study of the characteristics of stone covers on four lithologies in the late tertiary to quaternary basalt plateau of northeast jordan marked variations occur in clast dimensions and the characteristics of sorting between lithologies which are likely to affect hydrological response a more subtle control relating to slope conditions is superimposed on the lithological differences r and q mode factor analysis identifies groupings within the data which demonstrate the distinctiveness of different lithologies characteristics of the stone covers on sites affected by human occupation are markedly different from undisturbed sites on the same lithology

comparison of marine gravity from shipboard and high density satellite altimetry along the mid atlantic ridge 30 5 35 5 s we compare new marine gravity fields derived from satellite altimetry with shipboard measurements over a region of more than 120 000 square kilometers in the central south atlantic newly declassified satellite data were employed to construct free air anomaly maps on 0 05 degree grids sandwell and smith 1992 marks et al 1993 an extensive gravity and bathymetry dataset from four cruises along the mid atlantic ridge from 30 5 35 5os provides a benchmark for testing the two dimensional resolution and accuracy of the satellite measurements where their crosstrack spacing is near their widest the satellite gravity signal is coherent with bathymetry in this region down to wavelengths of 26 km t2 0 5 compared to 12 5 km for shipboard gravity residuals between the shipboard and satellite datasets have a roughly normal distribution the standard deviation of satellite gravity with respect to shipboard measurements is nearly 7 mgal in a region of 140 mgal total variation whereas the internal standard deviation at crossovers for gps navigated shipboard data is 1 8 mgal the differences between shipboard and satellite data are too large to use satellite gravity to determine crustal thickness variations within a typical ridge segment

the seasat altimeter mean sea surface model gridding techniques are used to combine an 18 day set of seasat altimeter data and two precisely computed seasat ephemerides in order to arrive at global contour maps of the mean sea surface topography the altimeter data have an rms agreement of 111 cm with the ss3 mean sea surface computed by means of the pgs s3 ephemerides and of 70 cm with the ss4 mean surface derived from the pgs s4 ephemerides while comparisons with the gem 10b 1 x 1 deg gravimetric geoid have yielded rms differences of 2 8 m those with a global mean sea surface derived from geos 3 altimeter data show rms differences of 1 3 m and 1 1 m for the cases of the ss3 and ss4 surfaces respectively an ss4 mean sea surface topograph is featured among the study findings presented further improvements in the representation of mean sea surface topography are expected with the development of more accurate gravity models for orbit computation

analysis of gravity and topography in the glimpse study region isostatic compensation and uplift of the sojourn and hotu matua ridge systems 1 the gravity lineations intraplate melting petrologic and seismic expedition glimpse experiment investigated the formation of a series of non hot spot intraplate volcanic ridges in the south pacific and their relationship to cross grain gravity lineaments detected by satellite altimetry using shipboard gravity measurements and a simple model of surface loading of a thin elastic plate we estimate effective elastic thicknesses ranging from 2 km beneath the sojourn ridge to a maximum of 10 km beneath the southern cross seamount these elastic thicknesses are lower than predicted for the 3 9 ma seafloor on which the volcanoes lie perhaps due to reheating and thinning of the plate during emplacement anomalously low apparent densities estimated for the matua and southern cross seamounts of 2050 and 2250 kg m 3 respectively probably are artifacts caused by the assumption of only surface loading ignoring the presence of subsurface loading in the form of underplated crust and or low density mantle using satellite free air gravity and shipboard bathymetry we calculate the age detrended residual mantle bouguer anomaly rmba the rmba corrects the free air anomaly for the direct effects of topography including the thickening of the crust beneath the seamounts and volcanic ridges due to surface loading of the volcanic edifices there are broad negative rmba anomalies along the sojourn and brown ridges and the hotu matua seamount chain that extend nearly to the east pacific rise these negative rmba anomalies connect to negative free air anomalies in the western part of the study area that have been recognized previously as the beginnings of the cross grain gravity lineaments subtracting the topographic effects of surface loading by the ridges and seamounts from the observed topography reveals that the ridges are built on broad bands of anomalously elevated seafloor this swell topography and the negative rmba anomalies contradict the predictions of lithospheric cracking models for the origin of gravity lineaments and associated volcanic ridges favoring models with a dynamic mantle component such as small scale convection or channelized asthenospheric return flow

surface sealing as influenced by slope angle and position of simulated stones in the top layer of loose sediments the influence of five different slope angles and two different positions of simulated stones in the top layer of a sandy and a silty sediment on surface sealing intensity is examined in the laboratory sealing intensity is assessed by studying changes of percolation rate through a sediment layer with simulated rainfall duration and by measuring cohesion of the 5 mm thick upper sediment layer a measure of seal strength by means of a torvane slope has a negative influence on sealing intensity for a constant per cent of simulated stone cover sealing intensity is lowest in the case of stones placed on the sediment surface compared to the case of stones pushed into the surface layer explanations for these findings are given and some implications are further discussed

bathymetric prediction from dense satellite altimetry and sparse shipboard bathymetry the southern oceans south of 30 s are densely covered with satellite derived gravity data track spacing 2 4 km and sparsely covered with shipboard depth soundings hundreds of kilometers between tracks in some areas flexural isostatic compensation theory suggests that bathymetry and downward continued gravity data may show linear correlation in a band of wave lengths 15 160 km if sediment cover is thin and seafloor relief is moderate at shorter wave lengths the gravity field is insensitive to seafloor topography because of upward continuation from the seafloor to the sea surface at longer wavelengths isostatic compensation cancels out most of the gravity field due to the seafloor topography we combine this theory with wiener optimization theory and empirical evidence for gravity noise to signal ratios to design low pass and band pass filters to use in predicting bathymetry from gravity the prediction combines long wavelengths 160 km from low pass filtered soundings with an intermediate wavelength solution obtained from multiplying downward continued band pass filtered 15 160 km gravity data by a scaling factor s s is empirically determined from the correlation between gravity data and existing soundings in the 15 160 km band by robust regression and varies at long wave lengths we find that areas with less than 200 m of sediment cover show correlation between gravity and bathymetry significant at the 99 level and s may be related to the density of seafloor materials in these areas the prediction has a horizontal resolution limit of 5 10 km in position and is within 100 m of actual soundings at 50 of grid points and within 240 m at 80 of these in areas of very rugged topography the prediction underestimates the peak amplitudes of seafloor features images of the prediction reveal many tectonic features not seen on any existing bathymetrie charts because the prediction relies on the gravity field at wavelengths 160 km it is insensitive to errors in the navigation of sounding lines but also cannot completely reproduce them therefore it may be used to locate tectonic features but should not be used to assess hazards to navigation the prediction is available from the national geophysical data center in both digital and printed form

gravity fields of the southern ocean from geosat data in august 1990 the u s navy declassified all geodetic mission gm radar altimeter data acquired by the geosat satellite over oceanic regions south of 60 s we have used these gm data in conjunction with the unclassified lower resolution geosat exact repeat mission erm altimeter data to construct high resolution gravity fields on a 5 km grid covering the annular region of the southern ocean which lies between 60 s and 72 s and encircles antarctica during the gm a complete mapping of the marine geoid between 72 and 72 n was accomplished the gm produced more densely spaced ground tracks typically 2 or 3 km at 60 s than those of either the erm or seasat consequently we were able to use the gm data to map the marine gravity field at a higher resolution than was previously possible using satellite altimeter data this paper describes the techniques we used to derive these gravity fields and image them these techniques involve 1 computing along track sea surface height slopes 2 gridding of these ascending and descending slopes 3 converting the slopes to conventional deflections of the vertical 4 transforming the deflections to gravity anomalies in the frequency domain and 5 imaging the resulting images of the marine gravity field reveal much that is new about the seafloor and the tectonic fabric of the southern ocean a region which includes large expanses of seafloor that have never been surveyed by ships

spatial patterns of soil water balance on intensively cultivated hillslopes in a semi arid environment the impact of rock fragments and soil thickness during past decades a diverse system of subsistence agriculture in south east spain annual rainfall of less than 300 mm has been overturned in favour of large scale plantations of almond trees without consideration for topography and related spatial patterns in soil hydrological properties the objective of this paper is to investigate the spatial pattern in soil physical properties induced by this cultivation system and to highlight its impacts on the water balance soil properties were recorded along hillslopes with shallow soils developed on slates and greywackes in the upper part of the guadalentin drainage basin murcia region frequent tillage of these almond plantations covering entire hillslopes has resulted in denudation by tillage erosion on the topographic convexities as well as transport of rock fragments and fine earth along the slopes these processes have created a systematic spatial pattern of soil thickness and rock fragment content shallow and stony soils on the topographic convexities and deep soils with a rock fragment mulch in the concavities at the foot of the slopes at the same time a negative relationship between rock fragment content and fine earth bulk density was observed the impact of this spatial pattern in soil properties on the water balance was evaluated using the pattern one dimensional hydrological and plant growth model the model simulates the water balance of soil profiles covering the observed variation in soil thickness stoniness and bulk density the model results indicate that the highest rates of infiltration evaporation and drainage as well as the lowest rates of overland flow are restricted to shallow soils on the hilltops in contrast the deeper soils in the valley bottoms produce a more stable moisture regime than shallower soils which tend to saturate and dry out quickly these model results are in agreement with the spatial patterns of almond productivity an asymptotic increase with soil thickness copyright c 2000 john wiley sons ltd

recent developments in high resolution global altimetric gravity field modeling in recent years dedicated effort has been made to improve high resolution global marine gravity fields one new global field is the danish national space center dnsc 1 minute grid called dnsc08gra released in 2008 dnsc08gra was derived from double retracked satellite altimetry mainly from the ers 1 geodetic mission data augmented with new retracked geosat data which have significantly enhanced the range and hence the gravity field accuracy

detecting the intertidal morphologic change using satellite data abstract the objectives of this study were a to generate an intertidal digital elevation model dem using waterlines extracted from landsat tm and in situ ground levelling data b to quantitatively estimate morphologic change from the generated dems for the years 1991 and 2000 and c to evaluate the chenier migration in the tidal flats of gomso bay korea on extracting the waterlines we considered the tidal flat environments such as tidal conditions remnant surface water suspended sediment and exposure time ground levelling was carried out along one line in 1991 and two lines in 2000 from the extracted waterlines and ground levelling data we succeeded in generating intertidal dems with an accuracy of 10 9 cm r m s overall and 7 3 cm r m s in the lower tidal flats the morphologic changes estimated by subtracting the two dems showed an erosion rate of 9 0 cm over 9 yr that corresponds to an annual mean morphologic change budget of 309 865 m 3 yr overall the gomso tidal flats can be defined as an erosion dominant environment the changes with respect to the sedimentary facies were also evaluated as a the sandy silt flat had a sedimentation rate of 3 4 cm over 9 yr that corresponds to an annual mean budget of 52 552 m 3 yr b the silty sand flat had a sedimentation rate of 14 3 cm over 9 yr that corresponds to a mean erosion of 197 927 m 3 yr and c the sand flat had a sedimentation rate of 11 8 cm over 9 yr that corresponds to a mean change of 58 808 m 3 yr the results comply with the general rules of sedimentology we also investigated the chenier migration which is the most dynamic geomorphologic change in the tidal flats chenier is usually composed by sand and shell as a result of coastal progradation in sand and it is dominantly fed by sediments transported by long shore currents the chenier was found to have migrated about 148 m landward over 6 yr the results demonstrate that satellite remote sensing is an efficient and effective tool for a long term morphologic change estimation in tidal flats

influence of atmospheric path delay on the absolute geolocation accuracy of terrasar x high resolution products two coupled investigations of terrasar x tsx high resolution data are described in this paper geometric validation and estimation of the tropospheric path delay using measurements of corner reflectors crs placed at different altitudes but nearly identical ranges the crs were placed within alpine and valley sites in switzerland where terrain diversity provides ideal territory for geometric validation studies geometric validation was conducted using slant range complex products from the spotlight and stripmap sm modes in ascending and descending configurations based on the delivered product annotations the cr image positions were predicted and these predictions were compared to their measured image positions to isolate path delays caused by the atmosphere six tsx sm scenes 35 x 50 km were examined containing four identical crs with the same ranges and an altitude difference of 3000 m the cr arrangement made it possible to verify the annotated tsx atmospheric path delay by comparing the predicted slant range with the slant range obtained by measuring the reflector image coordinates range differences between the high and low altitude reflectors helped to quantify small variations in the path delay both sm and spotlight tsx products were verified to meet the specified accuracy requirements even for scenes with extreme terrain variations in spite of the simplicity of the atmospheric model currently integrated into the processor small potential improvements of the geolocation accuracy through the implementation of more comprehensive atmospheric modeling were demonstrated

construction of an inter tidal digital elevation model by the water line method progress in the development of a method for constructing a digital elevation model dem of an inter tidal zone using remote sensing and hydrodynamic modelling is described the method allows the construction of an inter tidal dem over large areas relatively quickly as well as frequent subsequent monitoring of the dem to detect changes and is particularly suited to sar satellite data because of the all weather day night capability of sar the resulting dem may be used for the development of improved hydrodynamic models and for studying sediment mass transport in the inter tidal zone

resistance to overland flow on desert hillslopes abstract this study examines the relation between the darcy weisbach friction factor f and the reynolds number re for overland flow on six runoff plots in semiarid southern arizona the surfaces of these plots are irregular and covered with stones as overland flow increases the stones and microtopographic protuberances which constitute the major roughness elements are progressively inundated thereby altering the flow resistance analyses of 14 cross sections reveal that the resulting f re relations have two basic shapes convex upward and negatively sloping these shapes bear little resemblance to the conventional f re relation for shallow flow over a plane bed whose shape is a function of the state of flow rather they are explained in terms of the simultaneous operation of two processes the first is the progressive inundation of roughness elements and increase in their wetted upstream projected area as discharge increases this process causes f to increase the second is the progressive increase in the depth of flow over already inundated parts of the bed as discharge increases this process causes f to decline whether the f re relation has a positive or a negative slope depends on whether the first or second process dominates and this depends on the configuration of the bed and level of discharge these findings have profound implications for the mathematical modeling of overland flow on desert hillslopes whether a model is based on the saint venant equations or makes use of the kinematic wave approximation it requires the specification of a relation between f and re or surrogates thereof and the computed hydrograph is very sensitive to the form of this relation hitherto the most widely used relation has been the conventional one for shallow flow over a plane bed however the present study suggests that this relation does not apply to desert hillslopes additional field and laboratory studies are needed to learn more of the behavior and controls of f re relations on such hillslopes so that models of overland flow can employ more realistic relations and better simulate runoff hydrographs

influence of rock fragment coverage on soil erosion and hydrological response laboratory flume experiments and modeling two laboratory flume experiments on the effect of surface rock fragments on precipitation driven soil erosion yields were carried out the total sediment concentration the concentration of seven individual size classes and the flow discharge were measured digital terrain models dtms were generated before and after one of the experiments the results revealed that the rock fragments protected the soils from raindrop detachment and retarded the overland flow therefore decreasing its sediment transport capacity rock fragments were found to affect selectively the different size classes in a manner that changed according to the time scale for short times the rock fragment coverage reduced erosion of the finer particles 100 m was unaffected at long times the rock fragment cover decreased the concentration of the individual size classes in proportion to effective rainfall intensity and the area exposed to raindrops an area based modification of the hairsine and rose h r soil erosion model was employed to analyze the experimental data the h r model predictions agreed well with the measured sediment concentrations when high rainfall intensity and low rock fragment cover were used predictions were instead less accurate with low rainfall intensity and high rock fragment cover the dtm results showed that the presence of rock fragments on the soil surface led to increased soil compaction perhaps due to higher soil moisture content from greater infiltration within the rock fragment covered flumes

the potential use of digital image processing in geomorphology erosion of stony soils a case study summary techniques of digital image processing are now common place in remote sensing research this paper considers the potential use of some of these procedures on frame grabbed video images the example taken is that of the evolution of stone pavements and their implication for interrill erosion processes the results indicate a relationship between the total erosion loss and the rate of stone pavement areal cover in addition the paper shows how the technique could be of great assistance in the monitoring of many different types of environmental processes

can rock fragment cover maintain soil and water for saline sodic soil slopes under coastal reclamation abstract seeking a potential erosion control method for saline sodic soil slopes under coastal reclamation is essential we investigated the effect of rock fragment covers rc on the rainfall partitioning infiltration and runoff processes and the erosion processes for saline sodic slopes of 15 and 30 subjected to a 50 min simulated rainstorm with an intensity of 92 mm h 1 six rock fragment covers 0 10 20 40 60 and 80 were investigated soil was packed in 200 cm 100 cm 30 cm flumes divided into two to create two replicates for each treatment two sequential soil erosion events e1 followed by e2 were induced under two rainstorms that were 24 h apart results showed that in general rc had a positive effect on the runoff rate for both slopes a logarithmic relationship existed between the steady state infiltration rate and the rc for the gentler slopes an rc between 40 and 60 could protect the soil from erosion for e2 and e1 e2 events but did not do so for the e1 events alone for the steeper slopes the rc had no effect on soil losses for the e2 and e1 e2 events but increased the soil losses for the e1 events as the situation of rock fragment changed from situation 1 well embedded into the soil surface to situation 4 submerged in water the relationship between rc and soil loss became more complex and might change over time from a positive to a negative one the results suggested that the effect of rc on runoff and soil losses was influenced by the change of rock fragment situations over time during individual rainstorms the benefits of rc might be augmented by using them in combination with another protective measure

surface sealing as affected by various rock fragment covers in west africa field studies on the influence of rock fragments on surface sealing hence infiltration remain scarce and contradictory to document this issue rainfall simulation experiments were carried out on 37 undisturbed 1 m2 plots located along a pedo climatic transect across west africa an important part of the variability of infiltration coefficient r2 0 71 could be explained by a simple model based on the position of rock fragments in the top layer and accounting for the areal percentages of three types of soil surface 1 bare surface 2 soil surface covered with rock fragments embedded in the soil surface and 3 surface with rock fragments resting on top of the soil surface an even higher determination coefficient r2 0 76 was gained when rock fragment size were accounted for in combination with vesicular porosity furthermore a positive linear relationship was obtained between infiltration coefficient and mean annual rainfall suggesting that additional factors related to climate might be involved including organic matter content and clay mineralogy two main regions could thus be differentiated in the arid and semi arid zones coarse gravel and cobbles embedded in a seal are predominant and generate high runoff conversely fine and medium gravel mainly free at soil surface are dominant in the wetter zone favouring therefore higher infiltration rate

hydric properties of some spanish soils in relation to their rock fragment content implications for runoff and vegetation abstract physical and hydric characteristics of the upper three horizons average depth of sampling 0 0 25 0 25 0 60 and 0 60 1 20 m of 92 soil profiles of spain grouped according to the geological nature of the rock fragments on the soil surface or in the soil profile were studied mathematical relations were developed to separate the contributions of the fine earth fraction and of the fraction above 2 mm indexes were obtained that relate gravitational water and available water in the fine earth fraction with the values from total soil a multiple comparison statistical study was performed for the mean values of 1 rock fragment content 2 organic matter content 3 silt plus clay content 4 gravimetric water content at different suction values the linear correlations of the gravitational and available water indexes with the rock fragment content by volume as independent variable were studied they showed positive or negative effects of the increase of rock fragment content on both indexes depending on their petrographical composition finally conclusions related tothe development of vegetation and to the production of runoff have been drawn when rock fragment content increases the results show positive effects for the development of vegetation and for the production of saturation overland flow

flow resistance in concentrated overland flow on rough slope surfaces field experiments have been done on simulated flows over different rough pre rill and rill bed surfaces the purpose of the experiments was to evaluate the hydraulic roughness properties of these bed surfaces conventional equations describing the relation of the resistance coefficient to the reynolds number for flow in closed conduits or open channels can also be applied to shallow flows provided the boundary values of the reynolds number which discriminate between the various flow regimes are adapted when the reynolds number is less than 100 the flow regime is laminar above this figure the flow is either transitional or turbulent depending on the roughness of the bed surface the degree of turbulence can be deduced from a morphological description of the pre rill and rill bed surface roughness

effects of redistribution processes on rock fragment variability within a vineyard topsoil in mediterranean france in mediterranean vineyard landscapes to understand soil cover evolution at the landscape scale via soil redistribution one must take into account soil and land use specificities soils are characterised by large quantities of rock fragments and affect hydrological and erosion processes that have widely been published in the literature vineyards require a persistent cultivation pattern and soil tillage operations can often affect vertical and lateral rock fragment distribution the aim of this study is to analyse rock fragment content and variability in the topsoil 0 15 cm of a mediterranean vineyard to determine whether rock fragment distribution 2 64 mm at a farm plot is influenced by soil type and or linked to environmental parameters furthermore relationships between observed rock fragment distribution tillage and water erosion processes are discussed the field survey was based on a stratified sampling strategy taking into account soil type cultivation patterns and farm plot topography the results suggest that the effect of cultivation in the row inter row system is more pronounced than the previously inferred topographic effect the long term vineyard cultivation pattern induces spatial segregation of redistribution processes with cumulative effects over several years that are responsible for rock fragment spatial variability in topsoil

comparison of along track resolution of stacked geosat ers 1 and topex satellite altimeters cross spectral analysis of repeat satellite altimeter profiles was performed to compare the along track resolution capabilities of geosat ers 1 and topex data geophysical data records were edited differentiated low pass filtered and resampled at 5 hz all available data were then loaded into three dimensional files where repeat cycles were aligned along track 62 cycles of geosat exact repeat mission 16 cycles of ers 1 35 day orbit 73 cycles of topex the coherence versus wave number between pairs of repeat profiles was used to estimate along track resolution for individual cycles eight cycle average profiles and 31 cycle average profiles geosat and topex only coherence which depends on signal to noise ratio reflects factors such as seafloor gravity amplitude regional seafloor depth instrument noise oceanographic noise and the number of cycles available for stacking averaging detailed resolution analyses are presented for two areas the equatorial atlantic a region with high tectonic signal and low oceanographic noise and the south pacific a region with low tectonic signal and high oceanographic variability for all three altimeters along track resolution is better in the equatorial atlantic than in the south pacific global maps of along track resolution show considerable geographic variation on average globally the along track resolution 0 5 coherence of eight cycle stacks are approximately the same 28 29 and 30 km for topex geosat and ers 1 respectively topex 31 cycle stacks 22 km resolve slightly shorter wavelengths than geosat 31 cycle stacks 24 km the stacked data which are publicly available will be used in future global gravity grids and for detailed studies of mid ocean ridge axes fracture zones sea mounts and seafloor roughness

soil erosion and hydrology of the western mediterranean badlands throughout rainfall simulation experiments a review abstract rainfall simulation experiments are widely used in geomorphological research in badland areas this technique contributed significantly to our understanding of badland geomorphology in the mediterranean belt due to the different types of simulated rainfall applied and the variable size of the plots a review of the state of the art is necessary this study confirmed that rainfall simulations are well suited to i analyse runoff infiltration processes and sediment detachment within badlands and ii to establish the factors determining the hydrological and erosion response at interrill scale in badland areas the hydrological response of badlands is characterized by rapid responses low to moderate infiltration rates ranging from close to 0 to 55 mm h 1 and high runoff coefficients i e 60 positive relationships are observed between antecedent soil moisture content and rainfall intensity on the one hand and runoff coefficients on the other sediment concentration and soil detachment rates are among the highest measured on the mediterranean region i e up to 84 8 g l 1 and 4722 4 g m 2 h 1 results show that rainfall intensity runoff coefficient and slope angle have a positive influence on sediment concentration and sediment detachment in the case of rock fragment cover its influence is variable according to the soil cover percentage rainfall simulations increase our understanding of the temporal and spatial variability of the soil erosion processes however rainfall simulation provides mostly qualitative rather than quantitative information because of the small plot size and the simulated rainfall characteristics due to facility for repeating experiments and recording a high quantity of data in short time however this method allows the comparison amongst different environments and soil conditions as the rainfall properties can be reproduced

marine gravity of the southern ocean and antarctic margin from geosat in november of 1986 the u s navy satellite geosat began collecting unclassified gravity altimeter data as part of its exact repeat mission erm for national security reasons the geosat orbit was arranged so that it closely follows the seasat satellite altimeter ground track however there are two advantages of the geosat data over the seasat data first because of improvements in altimeter design geosat profiles are about 3 times more precise than seasat profiles this corresponds to an accuracy of 2 3 rad i e 2 3 mgal for wavelengths greater than 20 km second the geosat altimeter data were collected when the antarctic ice coverage was minimal february 1987 to march 1987 while seasat was only active during an antarctic winter june 1978 to september 1978 these new data reveal many previously uncharted seamounts and fracture zones in the extreme southern ocean areas adjacent to antarctica seven large age offset fracture zones apparent in the geosat data record the early breakup of gondwana finally the new data reveal the detailed gravity signatures of the passive and active continental margins of antarctica these data are an important reconnaissance tool for future studies of these remote ocean areas

can ash control infiltration rate after burning an example in burned calcareous and gypseous soils in the ebro basin ne spain abstract fire is a long established ecological factor that has shaped the life history hydrogeomorphological processes soil formation and landforms of mediterranean environments soil infiltration is one of the properties affected by fire as a consequence of litter and vegetation removal and heating of and changes to the biological chemical and physical soil properties in this context ash can play an important role in soil infiltration behavior and therefore affect sediment and runoff yield the aim of this work is to determine the effect of ash cover on infiltration rates a single ring infiltrometer was used immediately after a wildfire and before the first storm events to determine the soil infiltration rate a total of 24 infiltrations were made 2 soil types 2 treatments 6 replicates in each infiltration experiment the soil wetting front the bulk density and stoniness were also measured the results show that the final infiltration rate fc values are higher in calcareous soils than in gypseous soils the ash cover in calcareous burned soils only temporarily decreases the bulk density of topsoil and enhances infiltration

improved ocean geoid resolution from retracked ers 1 satellite altimeter waveforms summary the ocean geoid can be inferred from the topography of the mean sea surface satellite altimeters transmit radar pulses and determine the return traveltime to measure seasurface height the ers 1 altimeter stacks 51 consecutive radar reflections on board the satellite to a single waveform tracking the time shift of the waveform gives an estimate of the distance to the sea surface we retrack the ers 1 radar traveltimes using a model that is focused on the leading edge of the waveforms while earlier methods regarded adjacent waveforms as independent statistical events we invert a whole sequence of waveforms simultaneously for a spline geoid solution smoothness is controlled by spectral constraints on the spline coeycients our geoid solutions have an average spectral density equal to the expected power spectrum of the true geoid the coherence of repeat track solutions indicates a spatial resolution of 31 km as compared to 41 km resolution for the ers 1 ocean product while the resolution of the latter deteriorates to 47 km for wave heights above 2 m our geoid solution maintains its resolution of 31 km for rough sea retracking altimeter waveform data and constraining the solution by a spectral model leads to a realistic geoid solution with significantly improved along track resolution

patterns of rock fragment cover generated by tillage erosion abstract intensively cultivated areas in the upper part of the guadalentin catchment southeast spain show a systematic spatial pattern of surface rock fragment cover rc the objective of this paper is to quantify and to explain this spatial rock fragment cover pattern therefore a map of an intensively cultivated area of 5 km2 was digitised and for each pixel total topographic curvature was calculated next rock fragment cover was determined photographically at 35 sites with a range of total slope curvatures a linear relation between total curvature and rock fragment cover was found except for narrow concavities it was hypothesised that this pattern can be explained by a significant net downslope movement of rock fragments and fine earth by tillage the displacement distances of rock fragments by tillage with a duckfoot chisel were measured by monitoring the displacement of tracers painted rock fragments and aluminium cubes on 5 sites having different slopes the rare of tillage erosion for one tillage pass with a duckfoot chisel expressed by the diffusion constant k equals 282 kg m for up and downslope tillage and only 139 kg m for contour tillage nomograms indicate that mean denudation rates in almond groves due to tillage erosion 3 to 5 tillage passes per year can easily amount to 1 5 2 6 mm year for contour tillage and up to 3 6 5 9 mm year for up and downslope tillage for a field 50 m long and having a slope of 20 these figures are at least one order of magnitude larger than reported denudation rates caused by water erosion in similar environments hence tillage erosion contributes significantly to land degradation the downslope soil flux induced by tillage not only causes considerable denudation on topographic convexities hill tops and spurs and upper field boundaries but also an important sediment accumulation in topographic concavities hollows and valley bottoms and at lower field boundaries kinetic sieving i e the upward migration of rock fragments by the tines of the duckfoot chisel also concentrates the largest rock fragments in the topsoil in such a way that a rock fragment mulch develops in narrow valleys and at the foot of the slopes these results clearly indicate that tillage erosion is the main process responsible for the observed rock fragment cover pattern in the study area since the study area is representative for many parts of southern spain where almond groves have expanded since 1970 the results have a wider application they show to what extent intensive tillage of steep slopes has contributed to the increase in soil degradation to changes in hillslope morphology i e strong denudation of convexities development of lynchets and rapid infilling of narrow valley bottoms and to the development of rock fragment cover patterns which control the spatial variability of the hydrological and water erosion response within such landscapes

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

effects of agricultural practices on the hydrodynamics of a deep tilled hardened volcanic ash soil cangahua in ecuador abstract the rehabilitation of indurate pyroclastic formations of the ecuadorian sierra cangahua paves the way for the development of new agricultural areas the material derived from the fragmentation of the hardened volcanic ashes is strongly prone to pluvial erosion essentially because it has a fine silty sandy texture and because contains no organic matter and no clay minerals rainfall simulation was implemented before and after three cycles of cultivation to asses the evolution of soil structure and its susceptibility to erosion the cultivated plots were surface soil crusting occurred rapidly within the cultivated plots when compared to the recent tilled cangahua runoff and soil loss were generally higher on plots with lower structural stability and generally exhibited higher clay content in agreement with the structural stability measured in a laboratory organic matter inputs increase the soil porosity this condition had no effect on the structural stability of the soil resistance to crusting and therefore little impact on surface runoff and erosion the preferred option for land with these soils would be no tillage and a permanent soil cover pasture if they were to be utilised for agriculture

retracking ers 1 altimeter waveforms for optimal gravity field recovery summary we have reprocessed ers 1 radar altimeter waveforms using an algorithm designed to minimize sea surface slope error and decouple it from significant wave height swh error standard waveform retracking estimates three parameters arrival time swh and amplitude we show that errors in retracked estimates of arrival time and swh are inherently correlated because of the noise characteristics of the returned waveform this suggests that some of what is called sea state bias in the literature may be caused by correlated errors rather than true electromagnetic or skewness bias we have developed a retracking algorithm that reduces this error correlation and makes the resolution of sea surface slope signals independent of sea state the main assumption is that the swh varies smoothly along the satellite track over wavelengths of 90 km this approach reduces the rms error in sea surface slope to only 62 per cent of that of standard retracking methods while our method is optimized for gravity field recovery it may also improve the resolution of sea surface height signals of interest to physical oceanographers

the hydrological response of soil surfaces to rainfall as affected by cover and position of rock fragments in the top layer rainfall experiments have been conducted in the laboratory in order to assess the hydrological response of top soils very susceptible to surface sealing and containing rock fragments in different positions with respect to the soil surface for a given cover level rock fragment position in the top soil has an ambivalent effect on water intake and runoff generation compared to a bare soil surface rock fragments increase water intake rates as well as time of runoff concentration and decrease runoff volume if they rest on the soil surface for the same cover level rock fragments reduce infiltration rate and enhance runoff generation if they are well embedded in the top layer the effects of rock fragment position on infiltration rate and runoff generation are proportional to cover percentage micromorphological analysis and measurements of the saturated hydraulic conductivity of bare top soils and of the top layer underneath rock fragments resting on the soil surface reveal significant differences supporting the mechanism proposed by poesen 1986 i e runoff generated as rock flow or as horton overland flow can partly infiltrate into the unsealed soil surface under the rock fragments provided that they are not completely embedded in the top layer hence rock fragment position beside other rock fragment properties should be taken into account when assessing the hydrological response of soils susceptible to surface sealing and containing rock fragments in their surface layers a simple model based on the proportions of bare soil surface soil surface occupied by embedded rock fragments and soil surface covered with rock fragments resting on the soil surface describes the runoff coefficient data relatively well

a simple waterline approach for tidelands using multi temporal satellite images a case study in the yangtze delta abstract waterline technique based on satellite remote sensing is potentially one of the most effective tools for studying changes in tidal flat environment and coastlines however multi temporal waterlines obtained from satellite images are often difficult to compare directly because fluctuant tidal conditions may produce different elevation of waterlines to overcome the difficulty this study developed a comparable waterline solution to estimate active lateral evolutions using tm satellite images at different tide conditions owing to the dynamic properties the yangtze river mouth was selected as the case example to test the suitability of the approach and totally four time slices were partitioned during 1987 2004 for investigating coastline changes the first step of this technique is to digitize waterlines with various elevations labeling in a time slice in the second step the waterlines were merged to generate dems and contour maps using the linear gridding interpolation method in the last step any interested contour line may be extracted from dems and used for comparison of tideland changes to evaluate the errors in digitizing and interpolation process quantitative checks were examined after the dems were constructed in order to monitoring the rate of coastline spread a proposed approach for estimating mean coastline spread distance between two time spans is developed in this paper to conclude this work demonstrates the importance of tm etm images to provide high frequency historical topography and morphodynamics information for coastal monitoring and evaluation

comparison of geos 3 and seasat altimeter resolution capabilities a comparison is made between geos 3 and seasat altimeter data with regard to noise power spectral density psd derived geoid psd and short wavelength resolution at wavelengths greater than 450 km the noise psds for geos 3 and seasat are essentially the same and are attributed to mesoscale oceanographic effects at shorter wavelengths the noise spectra diverge because of the higher geos 3 instrument noise the average along track geoid psds are nearly identical between wavelengths of 4500 and 72 km the spectral coherence between repeat tracks shows that the short wavelength resolution of seasat data is 32 km and for geos 3 it is 60 km

accurate and efficient determination of the shoreline in ers 1 sar images extraction of the shoreline in sar images is a difficult task to perform using simple image processing operations such as grey value thresholding due to the presence of speckle and because the signal returned from the sea surface may be similar to that from the land a semiautomatic method for detecting the shoreline accurately and efficiently in ers 1 sar images is presented this is aimed primarily at a particular application namely the construction of a digital elevation model of an intertidal zone using sar images and hydrodynamic model output but could be carried over to other applications a coarse fine resolution processing approach is employed in which sea regions are first detected as regions of low edge density in a low resolution image then image areas near the shoreline are subjected to more elaborate processing at high resolution using an active contour model over 90 of the shoreline detected by the automatic delineation process appear visually correct

variation in soil chemical properties along toposequences in an arid region of the levant abstract detailed characterization of soils and their variation along different topography positions has not been investigated in depth for mediterranean arid regions there is a need to accurately understand the variation and the spatial distribution of soil properties within dry region of the levant such understanding is required to optimize the use and management of scarce land and water resources the objective of this study was to examine the effect of hillslope characteristics on the variation of selected soil chemical properties in an arid mediterranean climate at each of five selected transects four sites were chosen to represent four different topographic positions summit shoulder backslope and toeslope a soil profile was examined at each site and a representative sample from each horizon was withdrawn for chemical analyses the analyses indicated that generally the carbonate contents of the surface horizons decreased from higher to lower positions of the toposequence the carbonate content increased with depth for profiles occupying the lower positions this suggests more intense leaching within soil at lower positions the effect of steepness and curvature on controlling the variation of soil properties was obvious at the summit and shoulder positions leaching process seems to hinder the effect of steepness and curvature for soils at lower positions lower positions receive runoff water and organic matter from upper positions which complicate the relationship between landform shape and organic matter content continuous tillage resulted in lower organic matter contents for soils at lower positions higher ph values were reported for soils down along the transect due to the movement of soil material from upper hillslope positions electrical conductivity exchangeable calcium and potassium contents decreased downslope due to higher moisture accumulation however no obvious relationship was found between the variation of ph or ec in one hand and the variation of steepness and curvature on the other potassium content was variable due to its greater mobility the analyses indicated that variation in the soil cec is governed by two factors the leaching pattern which is controlled by hillslope position and the accumulation of eolian carbonates at the soil surface the distribution of iron oxides and types of clay minerals indicated more weathering in a descending direction and with soil depth which is attributed to higher availability of soil moisture along the same direction these relationships suggested systematic variation of chemical properties along toposequences in this arid environment

statistical characterization of geosat altimetry noise dependence on environmental parameters 1 sea surface height ssh measurements from the geosat satellite altimetry mission are analyzed to statistically characterize their noise process which is defined here as the small scale 50 km time varying component of the altimetry data this analysis is one component of a larger effort to extract meaningful information about seafloor roughness from the small scale fabric of the altimetric gravity field both small scale seafloor topography e g abyssal hills and ssh noise significantly influence the measured gravity fabric hence a global quantitative understanding of ssh noise is required to infer what portion of the gravity fabric is associated with the true geoid it is also anticipated that the ssh noise analysis will prove useful in designing improvements to altimetry processing algorithms the ssh data are first processed by differencing nearest neighbor tracks to minimize the static component of variability and then by high pass filtering to remove variability associated with mesoscale oceanic circulation autocovariance analysis reveals that ssh noise can be decomposed into uncorrelated white noise and correlated semiperiodic components three parameters are measured which characterize the variance of both components and the correlation length of the correlated component the global distribution of uncorrelated noise variance is closely correlated to significant wave heights directly linking the uncertainty of the altimeter return time to the roughness of the sea surface the variance and correlation length of the correlated component of noise can be associated with three separate environmental parameters sea ice precipitation rates and upper atmospheric variability associated with the subtropical jet stream as widely differing as these environmental processes are it is hypothesized that features like sea ice rain storms and atmospheric turbulence can cause sudden perturbations in the return time of the altimetry signal creating decaying oscillations associated with the onboard tracking algorithms

sar monitoring of progressive and seasonal ground deformation using the permanent scatterers technique spaceborne differential radar interferometry has proven a remarkable potential for mapping ground deformation phenomena e g urban subsidence volcano dynamics coseismic and postseismic displacements along faults as well as slope instability however a full operational capability has not been achieved yet due to atmospheric disturbances and phase decorrelation phenomena these drawbacks can often be at least partially overcome by carrying out measurements on a subset of image pixels corresponding to natural or artificial stable reflectors permanent scatterers ps and exploiting long temporal series of interferometric data this approach allows one to push the measurement precision very close to its theoretical limit in the order of spl sim 1 mm for c band european remote sensing ers like sensors in this paper the detection of both time uniform and seasonal deformation phenomena is addressed and a first assessment of the precision achievable by means of the ps technique is discussed results highlighting deformation phenomena occurring in two test sites in california are reported fremont in the southern bay area and san jose in the santa clara valley

controls of infiltration runoff processes in mediterranean karst rangelands in se spain semiarid karst landscapes represent an important ecosystem surrounding the mediterranean basin for which little is known on runoff generation knowledge of the sources and patterns of variation in infiltration runoff processes and their controls is important for understanding and modelling the hydrological functions of such ecosystems the objectives of this paper are to determine the infiltration rates and their controls in a representative mountain karst area sierra de gador se spain at micro plots and to investigate the integrated response of rainfall on a typical hillslope rainfall simulations in micro plots and natural rainfall runoff monitoring on a hillslope were carried out complementarily we investigated the role of soil surface components vegetation rock outcrop fracture and soil crust topographic position antecedent soil moisture and rainfall characteristics in regulating infiltration runoff processes results of rainfall simulation revealed the importance of vegetation cover and the presence of rock fractures in promoting the infiltration in the limestone karst landscape while bare patches and rock outcrops acted as sources for runoff all plots with 50 vegetation cover had no runoff with up to 55mmh 1 of simulated rain in contrast nearly all bare plots had runoff under the same simulated rain with runoff coefficients ranging from 3 1 to 20 6 on dry soil surface conditions and from 2 0 to 65 4 on wet soil surfaces runoff coefficients amounted to 59 0 79 5 for rock outcrops without cracks but were drastically reduced by the presence of cracks the surfaces with rock fragments resting on the soil generally located in the middle of the slopes prevented more effectively the runoff generation than those surfaces where rock fragments were embedded in the top soil antecedent soil moisture had significant impact on runoff generation with wet soil having doubled runoff coefficient shortened time to runoff and increased runoff rate compared to the same but dry soil linear regressions indicated that the main controls for constant infiltration rate were the cover percentages of vegetation and litter plus rainfall intensity while the major controls for runoff coefficient were the bare soil and vegetation coverage plus rainfall intensity high infiltration rates measured at the micro plots agreed with low intra event runoff coefficients mostly below 1 observed under natural rainfalls at the hillslope runoff depth and coefficient at the hillslope was significantly correlated with rainfall depth maximum hourly rainfall intensity and antecedent precipitation over 20days ap20 during the 1 5 year monitoring period from sep 2003 to mar 2005 the overall infiltration was 41 of the total rainfall amount and the maximum infiltration rate was almost 94 of the largest single rainfall event the results from this study contribute to improved understanding of the magnitude and controls of the surface runoff in semiarid karst mountain areas 2011 elsevier b v