tararua broadband array north island new zealand abstract the tararua broadband array consisting of nine three component seismometers was deployed in southern north island new zealand from february 1991 to september 1992 this l shaped array had an approximately 40 km n s arm and 30 km e w arm its primary purpose was to record waveforms from tonga kermadec earthquakes whose propagation paths have spent the majority of their time in the pacific plate that has been subducted beneath the australasian plate along the tonga kermadec hikurangi margin the continuous recording allowed simultaneous acquisition of an excellent teleseismic and regional broadband seismogram dataset for the main experiment broadband three component waveforms with p wave precursive slab phases up to 15 sec early relative to the jeffreys bullen travel times have been recorded for 71 events multiple frequency analysis of the p waveform shows that the high frequencies 5 hz arrive first with coherent dispersion below about 4 5 hz this behavior can be attributed to a high velocity layer 8 to 10 km thick lying above the cold fast lithosphere of the subducted pacific plate polarization analysis of the p wave precursors show them to arrive at steep incidence angles of 20 to 30 suggesting the phase refracts off the subducted plate9s surface to the array we observe exceptionally large pl leaking modes from shallow events in the tonga kermadec region to the north

influence of vegetal cover on sediment particle size distribution in natural rainfall conditions in a semiarid environment abstract sediment samples were collected during four years from two plots one covered by natural vegetation and the other a replica of the same plot from which the vegetation was removed manually disturbed plot in order to evaluate the effects of vegetal cover on sediment particle size distribution particle size was measured using a coulter ls130 laser diffraction device the effective size distribution of the sediment was compared with equivalent measurements of the same samples after chemical and mechanical dispersion ultimate size distribution to investigate the detachment and transport mechanisms involved in sediment mobilisation the ratio between the ultimate particle size composition of the transported sediment and that of the parent soil provided a measure of the particle size selectivity of the transported sediment the median effective particle was coarser than the median ultimate particle for almost all the events recorded in both plots confirming that much of the sediment in the runoff includes a substantial proportion of aggregates moreover the texture of the sediment was finer than that of the matrix soil with a depletion of clay and sand in exchange for an enrichment in silt indicating the existence of transport selectivity in both plots the effect of vegetal cover on the size distribution of the sediment was particularly evident after high intensity rainfall events an i30 of 40 mm h 1 was found to be the threshold value for changes to be produced in the sediment texture of the disturbed plot with aggregates being broken down and 10 20 more sand particles being observed at this value than after events of lower intensity no differences were found in the natural plot after rainfall of varying intensities the vegetal cover in the natural plot reduced the energy available for erosion from the rainfall by 50 and the energy from the runoff by 75 hindering the break down of aggregates and the transport of dense particles moreover the presence of vegetation meant the raindrop was the predominant contributor to soil loss in contrast to the disturbed plot where both raindrop and runoff contributed to the erosion

the effects of fire and water repellency on infiltration and runoff under mediterranean type forest abstract an investigation is being made into the relationship between forest fire and hillslope hydrology in the selva region of catalonia over a three year period at sites with a known fire history the major sites are on granite granodiorite or on sediments derived from these rocks at locations between santa christina d aro and santa coloma de farnes it appears that there is a general relationship between the type of organic profile found in a forest and the impact of fire in terms of loss of organic matter soil erosion hillslope hydrology and on the regeneration of the forest this paper summarises the results of about 150 rainfall simulation experiments and presents an overview of work carried out so far a major conclusion is that runoff processes are discontinuous and spatially structured due mainly to the effects of water repellency as a result of surface properties macropores hydrophobic behaviour and swelling four types of infiltration curve can be recognised at many locations infiltration increases with time during the early part of an experiment reaches a maximum value after about 30 minutes therupon subsequently decreasing this type of relationship can not be modelled with standard infiltration equations illustrations are given of sections through both burnt and unburnt soils to show how the hydrophobic effect influences water penetration it can be seen that infiltration patterns are similar for both burnt and unburnt soils and that micropores filled with organic matter are very important in conducting water through a water repellent surface layer the hydrophobic layer traps water in the bc horizon and prevents evaporation and loss by upwards capillary movement although the hydrophobic effects mean that small areas sometimes have a high runoff coefficient on larger areas there are many macropores and shrubs beneath which the soil is permeable and these trap runoff generated on the water repellent areas the main effect of fire is to illiminate the storage of water in the organic horizons several cm at first infiltration rates remain high but later these decrease as there is a reduction in porosity the sites having a moder type profile have better water retention properties more organic matter that survives the fire and a faster rate of vegetation recovery sites with a mor type profile can be degraded and erode if they are subject to disturbance the study provides another example of how on seemingly uniform slopes hydrological processes are structured by interactions with vegetation the patterns produced by these interactions survive the effects of fire

geomorphological impacts of a flood event on ephemeral channels in se spain a flood event occurred on 30 september 1997 in three catchments torrealvilla salada and nogalte in se spain which were being monitored for morphological change peak discharges were high in the torrealvilla catchment moderate in the salada and low in the nogalte detailed topographic surveys were made before and after the flood and from these dems of difference were constructed the two sites with highest flow both underwent significant incision of the channel at other sites both scour and aggradation of the channel took place with scour holes of up to 1 m depth eroded elsewhere within the channels major erosion took place downstream of tracks and structures such as check dams that impeded sediment movement the pattern and amounts of change show little relationship to independent factors other than a scale effect of peak discharge behaviour of channels is closely related to local sediment supply sediment flux calculated from changes in volumes at the site is comparable with the other figures produced for ephemeral channels and much higher than for perennially flowing streams

soil loss and soil water content affected by land levelling in penedes vineyards ne spain abstract this paper analyses the differences in soil moisture runoff and sediment concentration resulting from land levelling works carried out before new vineyard establishment in a reference wine region of ne spain in low disturbed soils low differences in soil moisture were observed while in high disturbed soils soil moisture and water infiltration of the surface were always lower than in the low disturbed ones while soil sealing was higher in high disturbed than in the low disturbed soils differences in runoff and sediment concentrations were also observed the most disturbed plot showed a higher sediment concentration in runoff which together with higher runoff volumes gave higher erosion rates and soil losses than the low disturbed one the differences within the most disturbed soils were high after high intensity rainfall events while no significant variations were observed in the least disturbed ones

flash flood and bedload dynamics of desert gravel bed streams comparatively little is known about the hydrology of desert flash floods despite the extent of the world s drylands there is even less known about their sedimentary behaviour and particularly about the movement of coarse material as bedload the results of an intense field monitoring programme carried out on an ephemeral gravel bed stream in the northern negev desert are presented in this semi arid setting flow duration analysis indicates that the channel is hydrologically active for 2 of the time or about seven days per year and that overbank flow can be expected for only 0 03 of the time about three hours per year multipeaked flood hydrographs are the norm reflecting many factors including the arrival of separate slugs of discharge from contributing subcatchments the passage of the initial flood bore is surprisingly slow but the rising limb of the flood hydrograph is rapid with a median time of rise of 10 minutes in keeping with expected flash flood behaviour bedload flux is high averaging 2 67 kg s 1 m 1 during the period that the channel carries flow this gives very high bedload sediment yield despite the infrequent and short duration of flood flows and matches the high yield of suspended sediment the relationship between bedload flux and boundary shear stress is simple in contrast with perennial gravel bed streams and the exponent of the log log relationship is 1 52 of great value is that the behaviour of the nahal eshtemoa corroborates a pattern established by the authors previously in a smaller tributary stream 1998 john wiley sons ltd

human impacts on fluvial systems in the mediterranean region the long history of substantial human impacts on the landscape of the mediterranean region and their effects on fluvial systems is documented these effects have included impacts of deforestation and other land use changes agricultural terracing on a wide scale water transfers and irrigation schemes during the 20th century major changes were made directly to channels through channelisation construction of dams of various sizes and extraction of gravel and indirectly by reforestation these changes have caused a major phase of incision on some rivers runoff and soil erosion have been affected by types of crops and agricultural practices as well as by the varying extent of cultivation and grazing some recent agricultural practices involve wholescale relandscaping of the topography and alteration of surface properties of material the importance of analysing the connectivity within different land units and of the spatial position of human activity within a catchment is illustrated the analysis of connectivity is the key to understanding the variability of impact and the extent of propagation of effects

measuring gullies by synergetic application of uav and close range photogrammetry a case study from andalusia spain abstract gullies naturally exhibit complex morphologies and hence are difficult to measure photogrammetric methods are promising tools to overcome such problems due to 3d reconstruction from overlapping images without disturbing the surface airborne e g unmanned aerial vehicles uav and terrestrial image acquisition platforms are possible data sources for comprehensive digital gully modelling in this study an approach for the synergetic utilisation of uav and terrestrial images for high resolution 3d model generation is introduced while proper uav mission planning is necessary terrestrial images can be acquired spontaneously and flexibly depending on the encountered terrain conditions to supplement uav data without confining accuracy demands terrestrial images are processed solely with additional information from already existent 3d models and orthophotos from uav image processing during this field campaign uavs are suitable for flexible and frequent gully monitoring however with the case specific flight configuration 3d modelling is restricted at steep gully walls above slope gradients of 50 60 as well as overhanging gully walls due to the limiting birds eye view additional terrestrial images are used to overcome these limitations and fill up data gaps in this study the final merged digital gully model reveals a resolution about 0 5 cm and an accuracy of 1 cm a gully headcut in andalusia spain is analysed to confirm the suitability of the synergetic data utilisation a study period of three months during winter season is investigated to measure multi temporal 3d volume changes the positive volume balance amounts to 5 m 3 for a gully area of 170 m 2 and is caused mainly by anthropogenic interactions concluding the combination of uav and terrestrial data allow for comprehensive gully models with high spatial resolution at frequent intervals

holocene aridification vegetation change sedimentation regime and limits of carbon isotope data as indicated by the alluvial pollen sites of arroyo grande and el molino in north central mexico abstract a multi proxy record of palynological sedimentological archaeological and carbon isotopic data of alluvial sites in the upper nazas basin arroyo grande durango 1855 m amsl and the parras basin el molino coahuila 1245 m amsl is introduced describing environmental changes across a short grassland desert ecotone from the eastern margins of the sierra madre occidental smo these sites reconstruct holocene vegetation history in semi arid north central mexico and integrate fluvial geomorphology and palynology data in particular pollen data links a rise of xeric flora with higher energy deposition and increased erosion in upland basins of the eastern smo according to archaeological finds at examined sites human occupation is linked to mesic or afforested conditions however limitations of carbon isotope data for environmental historical reconstruction are indicated by somewhat stable values at arroyo grande durango especially while pollen sites show a replacement of short grasses and park woodlands by a more xeric flora at higher elevations with a development of chihuahuan desert flora at low elevations el molino coahuila vegetation reconstructions are supported by pollen analog data collected from the cuatro cienegas region in coahuila mexico

morphological impacts of flow events of varying magnitude on ephemeral channels in a semiarid region abstract flows in ephemeral channels in semiarid areas are only occasional and channel changes are episodic but the flash floods can be devastating and have major geomorphological impacts data on morphological impacts of flows in semiarid areas are needed to increase understanding of the dynamics and variability of geomorphic responses in such channels for this purpose nine reaches of river channel in three catchments in se spain the nogalte torrealvilla and salada have been sites for measurement of flows and their effects over the period 1997 2012 the sites encompass a range of channel size channel morphology substrate vegetation and position within the catchments a major difference is between schist and marl bedrock areas peak flow stage has been recorded and topography surveyed at frequent intervals and after major flow events over the 16 year period an average of 0 5 flow events per year has been recorded at the schist sites and an average of one per year at the marl sites but occurrence has been highly variable from year to year threshold daily rainfall for channel flow is mostly 15 20 mm but higher rainfalls do not always produce flow one to two major floods have occurred in each of the catchments in the period including the extreme flood event of september 2012 in the nogalte catchment measured morphological changes have occurred between 2 and 10 times at the monitored sites the same size flow can have differing effects depending on the state of the system low flow can mobilise sediment without producing much morphological change the long term trajectory of the reaches and the sediment substrate has a major influence on response to events channel change is governed by threshold values of hydraulic conditions the measurements provide an indication of the scale of maximum erosion and deposition that occurs within the channels and on the floodplains over a range of flow magnitudes and the flow impacts that need to be considered in management

seasonal patterns of runoff and erosion responses to simulated rainfall in a badland area in mediterranean mountain conditions vallcebre southeastern pyrenees regolith surface characteristics and response were examined over a three year period in a badland area in a mediterranean middle mountain zone near vallcebre eastern pyrenees preliminary work carried out in this area indicated clear seasonal patterns of regolith properties driven by frost heaving in winter and crusting and erosion in the rest of the year rainfall simulations were performed with a small portable nozzle simulator in order to study seasonal changes in runoff generation erosion rates and raindrop effect on bulk density changes the results showed large seasonal variations in runoff and erosion responses in ltration rates after runoff start were correlated with precipitation depth before runoff start runoff generation was therefore related to regolith saturation only to a very limited extent erosion rates were more controlled by runoff rates than by the weakness of regolith against raindrop splash and sediment grain size increased with concentration the combined role of antecedent regolith moisture and bulk density explained most of the seasonal variability in in ltration bulk density changes during rainfall and erosion rates but some seasonal differences in sediment detachability were not explained by these variables and may be attributed to changes in roughness overall runoff and erosion responses were relatively stable during spring and autumn whereas wide variations in in ltration rates and sediment detachment occurred in winter and summer respectively experiments conducted in a single season would have produced poorly representative if not erroneous results copyright 2004 john wiley sons ltd

deriving indicators of soil degradation from soil aggregation studies in southeastern spain and southern france soil degradation is perceived as a major threat in the mediterranean region due to changes in land use and possible future climate change soil aggregation parameters are used here to demonstrate their potential as a key indicator for land degradation studies the monitoring of these indicators offers a means of establishing the vulnerability and resilience of geo ecosystems soil aggregation stability and distribution were studied on soils with an open shrubby vegetation cover from several places in southeastern spain and southern france by applying drop tests and determining aggregate size distributions aspect and vegetation cover were incorporated in the soil sampling several indices were derived from these analyses to indicate the degree of soil aggregation this was done by referencing to a base level of aggregation bare soil aggregation it was found that soil aggregates were more stable and were often coarser under vegetation when compared to their immediate surrounding bare areas a similar slightly less clear effect was noted on n facing exposed slopes when compared to s facing exposed slopes long term changes were found by studying cultivated land abandoned fields and land covered by semi natural vegetation on comparable substrate and comparable land units it is clear that soil aggregation and aggregate stability increases with time years it is argued that soil aggregation indices can be used as a key indicator for degradation processes at a fine scale with implications for runoff and sediment generating processes at the hillslope scale

correlated transient fluid pulsing and seismic tremor in the costa rica subduction zone continuous measurements of fluid flow were made over a six month period across the nicoya peninsula costa rica pacific convergent margin utilizing osmotically driven fluid flow meters designed to quantify both inflow and outflow rates on the order of 10 5 to 3 cm d significant transience in flow was observed through the surface of the forearc three periods of correlated flow signals were seen on the subduction forearc among three instruments located in the out of sequence thrust oost zone over along margin strike distances of 30 km amplitudes of ground velocity recorded on collocated ocean bottom seismometers obs increase during the three correlated flow events the seismic signal has frequency characteristics that resemble volcanic and non volcanic tremor we hypothesize that repeated plate boundary slow slip events potentially originating at the up dip limit of the seismogenic zone generate the observed signals within the toe of the forearc we propose a model in which the poro elastic stress strain field around a series of creep dislocations simultaneously forces flow through fracture networks in the forearc and oceanic basement rocks and induces diffuse flow through the shallow sediments the former generates the seismic tremor like noise recorded by the obss and the latter generates the flow transients recorded by the fluid flow meters we suggest that high sensitivity fluid flow meters can be utilized to detect transient tectonic strain events in offshore environments where traditional geodetic techniques lack resolution or are not possible d 2005 elsevier b v all rights reserved

the generation of infrasonic ambient noise in the ocean by nonlinear interactions of ocean surface waves expressions for the spectra of infrasonic ocean noise and microseisms induced by nonlinear wave interaction are derived theoretically for an ocean environment modeled as a water layer overlying a solid half space a series of spectral transfer functions relating the source pressure field induced by the wave action to the underwater acoustic noise field and that of the microseisms this generates in the seabed are defined and calculated the effect of bottom reflections on the transfer function is examined and an estimate of the contribution of the rayleigh wave component of the microseism signal received onshore is also made

delineating hydrological response units by geographical information system analyses for regional hydrological modelling using prms mms in the drainage basin of the river brol germany a modified concept of hydrological response units hrus for regional modelling of river basins using the prms mms model is presented the hrus are delineated by geographical information system gis analysis from physiographic basin properties such as topography soils geology rainfall and land use using a thorough hydrological systems analysis the hrus once classified by gis analysis preserve the three dimensional heterogeneity of the drainage basin the river brol basin a 216km 2 rheinisches schiefergebirge germany was selected to apply the concept in total 23 hrus were delineated and tested with the prms mms model using a 20 year hydrometeorological daily database the hydrological systems analysis revealed that interflow is the dominant flow process through the basin s slopes and the major contribution to groundwater recharge and river runoff this was accounted for by parameterizing the hrus in the model control file to drain their surplus water not used for satisfying the demand of evapotranspiration to a common conceptual subsurface storage this storage was simulated by interflow drainage to the groundwater aquifer in the valley floor which in turn drained to the channel network the prms mms model simulated the observed daily discharge very well and the fit was described by a daily correlation coefficient of r 0 91 the nasim and hspf models using different means to represent the basin s physiographic heterogeneity were applied to the brol basin as well but did not achieve this correlation the hru concept was found to be a reliable method for regional hydrological basin modelling and allows spatial up and downscaling future research on this concept will focus on incorporating the variable precipitation distribution into the classification of hrus and on the hydrodynamic routing of the modelled discharge additionally satellite imagery must be used for classifying land use in macroscale drainage basins

responses of interrill runoff and erosion rates to vegetation change in southern arizona abstract vegetation change fi om grassland to shrubland has occurred over much of the sonoran and chihuahuan deserts during the past century the effect of this vegetation change on interrill runoff and erosion was examined by conducting rainfall simulation experiments on large runoff plots on contemporary grassland and shrubland hillslopes these experiments show that compared to the grassland the interrill portions of shrubland hillslopes 1 have higher runoff rates 2 experience equilibrium runoff conditions much more frequently 3 exhibit higher overland flow velocities and 4 are subject to greater rates of erosion the environmental change that has led to the vegetation change has been relatively minor but its geomorphic impact has been substantial

terrestrial laser scanning soil surfaces a field methodology to examine soil surface roughness and overland flow hydraulics smith m w cox n j bracken l j 2011 terrestrial laser scanning soil surfaces a field methodology to examine soil surface roughness and overland flow hydraulics hydrological processes 25 6 842 860

spatial distribution of surface properties runoff generation and landscape development in the zin valley badlands northern negev israel in ltration tests soil mapping and soil property analysis were used to assess the effect of within storm rainfall conditions on spatial patterns of surface characteristics relevant for runoff generation continuity and erosion in the zin valley badlands runoff and erosion differ strongly between ridges and slopes soils at both locations are susceptible to sealing but on the sideslopes deep desiccation cracks inhibit continuous ow even during high magnitude rainstorms the discontinuous nature of runoff has a feedback on surface conditions erosion on the ridges maintains shallow soils prone to sealing while in ltration and deposition on the sideslopes enhance soil depth a prerequisite for stable desiccation cracks some runoff generated on the ridges is transmitted to the valley via rills on straight sideslopes rills are single and often discontinuous indicating limited frequency of continuous runoff along concave valley heads rill systems are well integrated and continuous concentrating runoff and reducing in ltration losses along slopes the longitudinal v shaped valley morphology of small catchments in the zin valley badlands re ects the long term effect of different erosion rates in valley heads and on sideslopes over time valley incision lengthened the sideslopes reducing the portion of annual rainfall that was runoff effective once sideslopes reached a critical length that inhibited frequent continuous ow a colluvium with an increased in ltration capacity developed reducing runoff frequency even further consequently erosion on the valley sideslopes decreased continuous ow from ridges to the valley channel remained more common in integrated rill systems in concavities and valley heads leading to more erosion and retreat of the valley heads the spatial patterns of runoff and erosion in the zin valley badlands demonstrate that landscape development is strongly affected by processes that lead to differentiation of soil properties on hillslopes with uniform lithology the patterns of surface characteristics and their role in landscape development are strongly dependent on rainfall conditions highlighting the need for geomorphologists to identify the dynamic spatial and temporal scales relevant for landscape development copyright 2004 john wiley sons ltd

measurement and prediction of ultralow frequency ocean ambient noise off the eastern u s coast ultralow frequency 0 02 2 hz acoustic ambient noise was monitored from january to april 1991 at six ocean bottom stations off the eastern u s coast the depths of the stations ranged from about 100 m to 2500 m the measured spectra are in good agreement with predictions made using cato s theory j acoust soc am 89 1076 1095 1991 for noise generation by surface wave orbital motion after extending the calculations to incorporate horizontally stratified environments contributions from both the linear single frequency virtual monopole and the nonlinear double frequency dipole mechanisms are clearly recognizable in the data the predictions make use of directional wave data obtained from surface buoys deployed during the swade experiment and an ocean bottom model derived from compressional wave speed data measured during the edge deep seismic reflection survey the results demonstrate conclusively that nonlinear surface wave interactions are the dominant mechanism for generating deep ocean ulf noise in the band 0 2 0 7 hz

effectiveness of vegetation barriers for marly sediment trapping vegetation barriers can be effective in trapping eroded sediment but little knowledge exists on the characteristics of vegetation barriers efficient in trapping all sediments from an eroded zone upslope the objective of this study is to quantify the effectiveness of vegetation barriers for marly sediment trapping relationships between eroded zones and vegetation barriers composed of low vegetation that is to say herbaceous and under shrub layers located downslope and sufficient to stop all the sediments eroded above have been studied in the brusquet experimental marly catchment in the french southern alps 40 plots with surface areas less than 500 m were studied the eroded zones and the vegetation barriers were characterised by their surface areas between which an average linear relationship exists results also showed that for a marly plot with a given surface area a downslope vegetation barrier covering only 20 of this plot can be sufficient to trap all the sediments eroded above it

differences in hillslope runoff and sediment transport rates within two semi arid catchments in southeast spain this paper focuses on hillslope runoff and sediment transport within two catchments in southeast spain five monitoring sites were established on hillslope concavities throughout the two catchments the techniques used were mini crest stage recorders spray painted lines sediment traps and tipping bucket rain gauges established during previous research results show that a storm event in the rambla nogalte on 30 june 2002 of 83 0 mm was responsible for a maximum runoff depth of 12 cm and a maximum hillslope sediment transport of 1886 cm3 m 1 the same storm in the rambla de torrealvilla produced 53 4 mm of rainfall on the 1 july 2002 had a maximum runoff depth of 26 cm and resulted in 2311 cm3 m 1 of sediment transport there is evidence to suggest that measured sediment transport is related to runoff and a qualitative estimate of morphological runoff zones mrz sediment transport and depth of runoff varied dramatically with lithology marl sites produced most runoff and sediment transport followed by the sites of mixed red and blue schist then blue schist these results are important for understanding the behaviour of slopes and show that for short lived storms with high but not rare rainfall intensities and total rainfall amounts runoff can cause significant hillslope sediment transport in semi arid areas

some factors controlling gully growth in fine grained sediments a model applied in southeast spain abstract gullies in the guadalentin catchment se spain are formed in a variety of lithologies ranging from schists to marls there are clear differences in valley and channel morphology between these two types gully erosion in schists produces large amounts of clastic material that restricts sediment transport leading to a relatively smooth transition from gullies to hillslopes and to broad alluvial valley bottoms with laterally migrating channels gullies in marls contain only limited gravels so gully extension leads to sharply incised gully heads a two dimensional model has been developed to investigate and simulate the distribution of gully heads in the guadalentin the model runs on a smooth initial surface with an added fractal perturbation without some perturbation of the initial surface or material properties symmetry prevents the formation of any channels fractal perturbation was used here to provide initial irregularities at all scales this paper explores the dependence of model response on the form of the sediment transport law initially sediment transport was considered to be transport limited and so depends on the relationship between wash and creep splash this was modified by i altering the exponents for gradient and area to conform with experimental results ii adding a critical tractive power for the initiation of rillwash iii including a more explicit treatment of mass movements iv including terms to reduce the dependence of the model on the computational grid size v providing a basis for explicitly integrating from individual storms to average long term behaviour and most critically vi introducing the effective bedload fraction ebf as a simplifying concept to allow for the selective transportation of eroded sediment this modification allows the model to represent removal of fines in marl rich catchments without the need to introduce a fully explicit travel distance formulation the steep gully heads and vertical side walls developed in marl catchments in the guadalentin basin are qualitatively well represented by the model preliminary tests showed that steep walled gullies are generated where the ebf falls to below about 0 5 if a tractive power threshold is also introduced gentler headcuts are produced selective transportation is thus seen as the critical determinant of steep headcuts in gully systems

unravelling late pleistocene and holocene landscape dynamics the upper guadalentin basin se spain abstract landscapes in se spain have developed in response to tectonics climate fluctuations and more recently human activity fluvial and colluvial sediments such as river terraces and slope deposits found in the valleys reflect a complex interplay between landscape forming processes investigating these sediment archives we reconstructed landscape evolution for the upper guadalentin basin se spain placing recent erosion processes in a landscape evolution context palaeo lake sediments dated between 17 and 13 8 ka evidence that a late glacial lake existed in the area probably formed by a sudden blockage of the guadalentin river differences in relative height above the floodplain and age between the river terraces of parts of the guadalentin river indicate that they have not been in equilibrium in the late quaternary deposition of river terraces along the upstream part of the river is recorded at 13 and 9 5 ka whereas no evidence of deposition is found for that period along the lower part of the river there episodes of sedimentation occur at 7 5 5 ka 3 4 1 6 0 7 and 0 4 ka this discrepancy is explained by the palaeo lake and its influence on erosion and sedimentation processes through base level changes combining these processes we propose a schematic model of late pleistocene and holocene landscape evolution from the model we can conclude that i the influence of the palaeo lake on deposition and erosion processes both upstream and downstream is evident and for the younger river terraces that ii episodes of deposition seem to coincide in time but iii episodes of erosion in between terrace level aggradation do not coincide and neither do terrace level heights and iv no evidence of deposition is found for the upstream part of the river correlation of erosion and sedimentation episodes with climate change and human impact is discussed although some correlations can be made there is strong evidence that climate was not the main driver of landscape processes we suggest that internal dynamics and local processes are more important drivers for landscape dynamics in the upper guadalentin basin than external and regional factors

runoff generation sediment movement and soil water behaviour on calcareous limestone slopes of some mediterranean environments in southeast spain abstract an interpretation of soil hydrology and erosion data obtained from limestone areas in southeast spain is presented in the framework of recent hypotheses on runoff generation mechanisms in mediterranean environments the main objective is to synthesise and harmonise the data in theoretical concepts or behavioural models of hydrological functioning of mediterranean limestone slopes for this purpose data were collected in a typical limestone area with climatic characteristics ranging from subhumid to semiarid several sites were chosen with comparable slopes vegetation and soils along a transect of 20 km to carry out several research projects the data discussed in this paper consist of information on water redistribution within the soil profiles obtained from long duration up to 5 h rainfall simulation experiments with continuous monitoring of soil moisture at different depths runoff and sediment concentration data were obtained i from rainfall simulation experiments with different antecedent soil moisture conditions and ii as natural results from open gerlach plots on runoff and sediment movement over 4 years three conceptual models of water redistribution during the infiltration process could be observed two of them imply nonuniform water redistribution within the soil profile due mainly to macropore flow caused by specific soil surface characteristics at the plot scale runoff generated in bare patches is mainly hortonian in plots with previously wetted soils or soils with high infiltration capacities the generated runoff implies the saturation of the upper soil both types of runoff are discontinuous through time and space the runoff generation mechanisms at the slope scale have been synthesised into two conceptual models a hortonian discontinuous runoff model that takes place in the most degraded slopes or during high intensity rain events and a mixed runoff generation model in less degraded slopes or in previously wet soils where infiltration excess runoff as well as saturation excess runoff can happen on the same slope in both cases slopes behave as a patchwork of runoff and runon areas the size of the runoff or runon patches is dependent on the climatological conditions these control the hydrological disconnection between different parts of the slopes hortonian and saturation runoff can both be generated and infiltrated downslope

passive underwater acoustic evolution of a calving event direct measurements of processes occurring at the ice ocean boundary are difficult to acquire because of the dangerous and dynamic nature of the boundary yet these processes are among the least well understood in glaciology because sound travels well through water passive underwater acoustics offers a method to remotely sense activity at this boundary here we present passive acoustic measurements and spectral analysis of the evolution of a subaerial calving event and the subsequent mini tsunami and seiche at meares glacier alaska usa using two hydrophones to record sound from 1 to 40 000 hz we find that each phase of a calving event has distinctive spectral characteristics an event begins with an infrasound rumble 1 20 hz then the ice fractures 20 100 hz falls and impacts the water 200 600 hz high frequency 10 000 hz sound increases in intensity quickly as the iceberg oscillates creating turbulence spray and waves within 10 s the low frequency audible sound dissipates and the mini tsunami and seiche sounds dominate infrasound plus high frequencies and continue for over 10 min the specific frequencies and duration of each phase of a calving event depend on its size and location and the glacier and fjord characteristics