investigation of the relationships between basin morphology tectonic uplift and denudation from the study of an active fold belt in the siwalik hills central nepal the present study investigates correlations between an extensive range of geomorphic properties that can be estimated from a digital elevation model and the uplift rate on geological timescales the analysis focuses on an area in the siwalik hills central nepal where lithology and climate can be considered as uniform this area undergoes rapid tectonic uplift at rates of up to 15 mm yr 1 which are derived from the geometric pattern of a fault bend model of fold growth the selected geomorphic properties can be divided in two categories depending on whether or not the vertical dimension is taken into account none of the planar properties are significantly correlated to uplift rate unlike those that include the vertical dimension such as the mean elevation of basins hypsometric curve and hypsometric integral and relief defined by the amplitude factor of length scaling analysis correlation between relief and uplift rate is observed for all length scales of topography shorter than 600 m which suggests that all orders of the streams are able to adjust to the tectonic signal simple mass balance considerations imply that the average elevation is only 10 of surface uplift suggesting that a dynamic equilibrium has been reached quite rapidly using a simple two process model for erosion we find that fairly high diffusion coefficients order of 10 m 2 yr 1 and efficient transport of the material by rivers are required this unusually high value for mass diffusivity at small length scales may be obtained by either a very efficient linear diffusion or by landsliding actually both processes may be active which appears likely given the nature of the unconsolidated substratum and the favorable climatic conditions local relief in the study area may therefore be used to predict either uplift or denudation but the prediction is calibrated only for that specific climatic and lithologic conditions and cannot be systematically applied to other contexts

controls of climate topography vegetation and lithology on drainage density extracted from high resolution topography data summary mark melton in 1957 found that climate basin morphometry and surficial variables control drainage density d d but differences observed between field surveyed channels and those mapped on topographic contours or blue lines left doubts on these results later several landscape evolution model and observational studies analyzed the behavior of d d however only a few studies have been performed over a large number of landscapes of different characteristics and have relied on high resolution topography data we revisit melton s hypothesis by using meter resolution digital terrain models dtms in 101 subbasins in the usa we first propose a dimensionless drainage density d dd metric based on the ratio of likely channelized pixels to total number of basin pixels which has the advantage of eliminating the computation of the channel network our analysis shows that d dd is a weak scaling function of the input dtm resolution compared to the classic dimensional d d metric ratio of total channel length to total basin area we analyze the correlation of d dd and mean annual precipitation map with a gaussian mixture model which identifies two sub groups displaying different correlation negative in arid and semi arid environments and positive in humid environments the transition in correlation is around 1100 100 mm yr of map and is accompanied by the occurrence of thick soil layers and high available water capacity that promote dense vegetation cover v cov and low d dd while small variation in d dd is observed across vegetation types increasing v cov corresponds to decreasing d dd we also explore the relationship between d dd and relief r and d dd and lithology d dd and r are weakly correlated in arid and semi arid environments while they have strong positive correlation in humid environments no significant correlation is found between d dd and lithology although the results are likely affected by our sample choice

evidence for large scale eddy driven gyres in the north atlantic analysis of a recent climatological database for the north atlantic has detailed an extensive large scale recirculation system in the intermediate waters of the north atlantic basin the pressure fields that define this recirculation coupled with the potential vorticity fields associated with the recirculating flow provide observational evidence for basin scale eddy driven flow in the global ocean the recirculations are intimately tied to the waters carried southward by the deep western boundary current and are therefore likely to affect the distribution of climatic anomalies in the north atlantic

morphologic stratigraphic and morphometric investigations of valley networks in eastern libya montes mars implications for the noachian hesperian climate change dendritic valley networks and broad longitudinal valleys are widespread within the eastern libya montes region the morphologic characteristics of the studied dendritic valleys especially their occurrence at local summits provide evidence for the initial formation by surface runoff due to atmospheric precipitation whereas the longitudinal valley systems are thought to have been formed and modified by groundwater induced processes our crater counts and model ages show that the dendritic valley networks average age 4 0 ga formed earlier than the longitudinal valley systems average age 3 7 ga both fluvial forms indicate a temporal change of the erosive environment at the noachian hesperian transition at 3 8 ga our results suggest that the fluvial activity within our investigation area lasted for 800 my from 4 1 ga to 3 3 ga the dendritic valleys show valley densities between 0 12 km 1 and 0 57 km 1 indicative of highly mature and integrated valley systems that we interpret to be characteristic of warmer and wetter conditions on mars

evaluation of morphometric parameters of drainage networks derived from topographic maps and dem in point of floods an evaluation of morphometric parameters of two drainage networks derived from different sources was done to determine the influence of sub basins to flooding on the main channel in the havran river basin balikesir turkey drainage networks for the sub basins were derived from both topographic maps scaled 1 25 000 and a 10 m resolution digital elevation model dem using geographic information systems gis blue lines representing fluvial channels on the topographic maps were accepted as a drainage network which does not depict all exterior links in the basin the second drainage network was extracted from the dem using minimum accumulation area threshold to include all exterior links morphometric parameters were applied to the two types of drainage networks at sub basin levels these parameters were used to assess the influence of the sub basins on the main channel with respect to flooding the results show that the drainage network of sub basin 4 where a dam was constructed on its outlet to mitigate potential floods has a lower influence morphometrically to produce probable floods on the main channel than that of sub basins 1 3 and 5 the construction of the dam will help reduce flooding on the main channel from sub basin 4 but it will not prevent potential flooding from sub basin 1 3 and 5 which join the main channel downstream of sub basin 4 therefore flood mitigation efforts should be considered in order to protect the settlement and agricultural lands on the floodplain downstream of the dam in order to increase our understanding of flood hazards and to determine appropriate mitigation solutions drainage morphometry research should be included as an essential component to hydrologic studies

eddy mean flow interaction in the gulf stream at 68 w part ii eddy forcing on the time mean flow abstract data front the synop 68 w current meter array show a trough pattern in the 26 month mean gulf stream path at 68 w and a cyclone in the mean deep flow in order to determine whether eddies are controlling the speed and direction of the time mean gulf sream flow at 68 w a theory is developed that extends the eliassen palm theory for zonal mean flows to time mean flows the eddy force is evaluated as the three dimensional divergence of an eddy stress tensor and is equivalent to the eddy advection of momentum fmom and the rotated divergent eddy stretching potential vorticity flux ftherm the study region at 68 w is characterized by large amplitude trough formation events it is shown that ftherm is associated with the growth stage of the eddy trough formation events and tends to turn the upper level time mean flow southward into the trough pattern and accelerate and spin up the deep layer cyclone fmom has a vertically coherent pattern associated with the decay stage of the trough formation events

controls on fan development evidence from fan morphometry and sedimentology sierra nevada se spain abstract we have studied the morphology and the morphometric relations between alluvial fans and drainage basins in a bajada system including more than 20 coalescent fans developed since the late pleistocene as a result of the recent uplift of the sierra nevada betic cordillera spain three allocycles of tectonic origin were recognised across which there is a clear evolution from debris flow to sheet flow dominated fans in connection with a decrease in the volume of fines available in the source areas the larger volume of accommodation space created by higher tectonic subsidence in the northern sector favoured vertical accumulation of sediment with the appearance of less elongated fans in the rest of the system where subsidence is less more elongated fans appear with the development of incised channels and irregular distribution of sediment in depositional lobes this involves the appearance of markedly asymmetric transverse profiles as well as lengthy recurrence between the sedimentation events on particular sectors of the fans where headward eroding gullies develop the lithology of the source area where intensely fractured rocks are found is responsible for an important sediment supply and a significant degree of clast sorting from the source area consequently a weak longitudinal trend in particle size can be recognised which influences the predominance of longitudinal constant slope profiles and anomalous relations between both fan area and fan slope and their drainage areas recent intense tectonic activity has caused the appearance of abnormally low slopes in upper sectors of some catchments where mass flows are trapped and the fans present a subsequently higher proportion of sheet flows recent piracy phenomena can be recognised in some of the drainage basins which indicate rejuvenation of the source area in which case the fan presents a rapid increase in the proportion of mass flows with the development of a segmented longitudinal profile due to the recent nature of the processes the morphometric relations in the fan fed by the basin affected by capture do not coincide with the other fans in the area

scaling relationships of channel networks at large scales examples from two large magnitude watersheds in brittany france abstract we present a statistical analysis on two watersheds in french brittany whose drainage areas are about 10 000 and 2000 km 2 the channel system was analysed from the digitised blue lines of the 1 100 000 map and from a 250 m dem link lengths follow an exponential distribution consistent with the markovian model of channel branching proposed by smart 1968 the departure from the exponential distribution for small lengths that has been extensively discussed before results from a statistical effect due to the finite number of channels and junctions the strahler topology applied on channels defines a self similar organisation whose similarity dimension is about 1 7 that is clearly smaller than the value of 2 expected for a random organisation the similarity dimension is consistent with an independent measurement of the horton ratios of stream numbers and lengths the variables defined by an upstream integral drainage area mainstream length upstream length follow power law distributions limited at large scales by a finite size effect due to the finite area of the watersheds a special emphasis is given to the exponent of the drainage area a a that has been previously discussed in the context of different aggregation models relevant to channel network growth we show that a a is consistent with 4 3 a value that was obtained and analytically demonstrated from directed random walk aggregating models inspired by the model of scheidegger 1967 the drainage density and mainstream length present no simple scaling with area except at large areas where they tend to trivial values constant density and square root of drainage area respectively these asymptotic limits necessarily imply that the space dimension of channel networks is 2 equal to the embedding space the limits are reached for drainage areas larger than 100 km 2 for smaller areas the asymptotic limit represents either a lower bound drainage density or an upper bound mainstream length of the distributions because the fluctuations of the drainage density slowly converge to a finite limit the system could be adequately described as a fat fractal where the average drainage density is the sum of a constant plus a fluctuation decreasing as a power law with integrating area a fat fractal hypothesis could explain why the similarity dimension is not equal to the fractal capacity dimension as it is for thin fractals the physical consequences are not yet really understood but we draw an analogy with a directed aggregating system where the growth process involves both stochastic and deterministic growth these models are known to be fat fractals and the deterministic growth which constitutes a fundamental ingredient of these models could be attributed in river systems to the role of terrestrial gravity

climatic and tectonic controls on alluvial fan and axial fluvial sedimentation in the plio pleistocene palomas half graben southern rio grande rift abstract six steep 0 6 4 3 short radial length 1 5 5 km deeply incised pliocene to early pleistocene paleofans and associated axial fluvial strata are preserved adjacent to the footwall of the palomas half graben in the southern rio grande rift two different scales of interbedding of lithofacies are evident in the exposed basin fill sediment the footwall derived alluvial fan strata are arranged into 3 10 m thick cyclothems representing three events 1 development of calcic paleosols that were contemporaneously or subsequently truncated by channels up to 4 m deep 2 infilling of channels by turbulent flow horizontally bedded and cross bedded conglomerates and 3 deposition of hyperconcentrated flow pebbly sandstones these cyclothems probably resulted from paleoclimatic changes on the scale of 150 kyr on a larger geographic and temporal scale the axial river ancestral rio grande which primarily deposited cross bedded pebbly sand experienced kilometer scale lateral movement toward the footwall block resulting in one thick 80 m axial fluvial lithosome in the northern part of the basin and two or three thinner 8 25 m axial fluvial lithosomes in the south a protracted period of fault movement and consequent basin tilting was the probable driving force behind lateral movement of the river and toe cutting of the fans by the river was the dominant process

river terraces and alluvial fans the case for an integrated quaternary fluvial archive abstract the fluvial archive literature is dominated by research on river terraces with appropriate mention of adjacent environments such as lakes despite modern sedimentary basins comprising a significant 88 volume of distributive fluvial systems of which alluvial fans 1 km

scaling and elevation in river networks the analysis of large river networks obtained from digital elevation models has given insight into the variation of channel slope with scale investigators have recently suggested that channel slopes are self similar with magnitude or area as a scaling parameter our data indicates otherwise in particular the variance of channel slope is larger than that predicted by simple self similarity this suggests multiscaling the scaling exponent for the standard deviation is approximately half the corresponding exponent in the relationship of the slope mean to magnitude or area a model for channel slopes based on a point process of elevation drops along the channel is presented the model reproduces observed multiscaling properties when the density of elevation increments is related to area or magnitude as a

alluvial fans on volcanic islands a morphometric perspective sao vicente cape verde abstract the distribution morphology and development of volcanic island alluvial fans are investigated using sao vicente from the cape verde volcanic chain east central atlantic ocean this is a tectonically and volcanically inactive dryland setting comprising an eroded plio pleistocene composite volcano overlying a submarine shield volcano we mapped 228 alluvial fans quantifying fan f and catchment c morphological properties area a gradient g relief r length l fans and catchments of varying size and gradient are distributed around the island coastal margins 6 and along interior valley sides 94 regression results i e ve ve slopes of best fit lines conformed to broader fan research but with weak correlations and coefficient exponent values outside or at the lower end of values reported from non volcanic settings analysis of fan area and gradient vs catchment area regression residuals revealed fans were dominated by small steep gradient 28 and large low gradient forms 39 fan building space is a fundamental control specifically linked to volcano structure but with interplay between rock strength base level and climate fans around the volcanic edifice flanks are uncommon due to steep flank slopes where flank margin fans occur they are typically small and steep forms due to marine erosion fans along flank incised valleys are common large low gradient fans are associated with a major volcanic rift aligned valley structure with extensive erosion into altered and weathered edifice core lithologies small steep gradient fans are associated with edifice flank valleys steeper and narrower valley forms reflect incision into stronger lithologies of the composite volcano flanks restricting fan building space fans located within the volcano central depression are amongst the largest and lowest gradient types building into the eroded and unconfined edifice core space coalescence apex toe incision toe erosion and catchment stream channel backfilling displayed by most fans suggest landscape erosion dominates during more arid periods e g interglacials with the dryland setting generating limited sediment and insufficient flood runoff for transport and fan deposition fan building likely occurs during wetter periods linked to quaternary climate variability quaternary eustatic variations are relevant for the volcano edifice margins where sea level changes control fan building space and erosion

channel networks a geomorphological perspective the study of channel networks has been dominated since 1966 by the random model however recent work has shown 1 that although the topological properties of small networks conform to the random model more closely than those of large ones even small networks exhibit systematic deviations from topological randomness and 2 that the topological and length properties of channel networks are controlled to a large degree by the spatial requirements of subbasins and the need for these subbasins to fit together in space by the size sinuosity and migration rate of valley bends and by the length and steepness of valley sides the factors that control the density properties of channel networks vary with the scale of the investigation and the geomorphic processes governing channel initiation although progress has been made toward a satisfactory stream junction angle model further work is needed the evolution of channel networks has been investigated by a variety of methods including the development of conceptual and simulation models the monitoring of small scale badland and experimental drainage basins and the substitution of space for time the morphology of most channel networks is largely inherited from the past or strongly influenced by inherited forms inasmuch as there is no way of ever knowing the origin or complex history of such networks the use of stochastic models in their study seems unavoidable

factors influencing the presence or absence of tributary junction fans in the iberian range spain this paper analyses the factors which influence the presence or absence of tributary junction fans in the iberian range northern spain two valleys were selected both characterised by wide variations in lithology altitude land use and plant cover two groups of factors were studied those related to the internal characteristics of the drainage basins which particularly control sediment generation and those related to the characteristics of the depositional area which control accommodation space and main river power among the internal factors the development of alluvial fans was related to i the capacity of the basin to yield large volumes of sediment ii the occurrence of intense human pressure until recent times a good indicator of sediment yield and iii the capacity of the basin to quickly increase discharge during rainstorms discharge density and torrentiality it is suggested that the areas that were intensively cultivated in the past and have therefore been affected by intense erosion have played a decisive role on the development of alluvial fans this would imply that many of these alluvial fans have a relatively recent origin perhaps related to the beginning of a widespread deforestation the basins without alluvial fans are characterised by relatively steep hillslope gradients that is slopes that never were subjected to historical cultivation low drainage densities and dense forest and shrub cover mostly coinciding with high altitude basins composed of quartzite and shale bedrocks regarding the external factors the shape size and longitudinal gradient of the main river to which the fans are tributary are the most relevant conditioning factors determining the development of alluvial fans

gis multi criteria decision analysis for assessment and mapping of neotectonic landscape deformation a case study from crete this study of drainage systems in a tectonically active region is based on the geographical information systems gis integration of data from an analytic hierarchy process ahp and a weighted linear combination wlc procedure with multiple criteria data a set of thematic maps were produced based on existing geological maps and freely available aster global dem elevation data using various geological information i e lineaments and lithologies geomorphometric indices i e slope gradient drainage density stream frequency and the topographic wetness index and morphotectonic indices i e amplitude of relief and stream length gradient that highlight areas of neotectonic landscape deformation the weights of the factors were determined using ahp and wlc a neotectonic landscape deformation index nldi is computed as the sum of the various weighted factors to provide a map of nldi distribution across the study region western crete the main objective of this study was to analyse and map the intra basin spatial variations in neotectonic landscape deformation five classes very low to very high were determined high to very high deformation zones are linked with known and newly detected active fault zones the methodology could be developed into a low cost technique for assessing seismic hazard guiding disaster risk reduction activities it can provide an alternative to the interferometric synthetic aperture radar insar approach for highlighting zones of neotectonic deformation particularly in regions where dense vegetation or snow cover renders insar ineffective

the ventilation of the world s oceans maps of the potential vorticity field abstract maps of potential vorticity q within four different density layers are presented for the north and south atlantic north and south pacific and indian oceans potential vorticity is evaluated as f 0 z a prescription that is valid for large slow scales and that allows its mapping from hydrographic data alone here f is the coriolis frequency p0 the potential density and z the vertical coordinate it is shown that the character of a layer within the thermocline of a subtropical gyre will vary greatly depending on the extent to which the layer is isolated from surface boundary conditions and forcing fluid particles recirculating within ventilated layers have their potential vorticity and other properties reset with virtually every circuit round the gyre when they pass through the outcrop zone by contrast particles within unventilated or dynamically isolated layers have time to share their properties with neighboring particles and approach a common homogenized state the north

effects of lithology and geomorphology on sediment yield in karst mountainous catchments abstract due to the characteristics of the lithology and the complexity of the geomorphology the karst areas of southwest china are experiencing severe soil erosion knowledge of the effects of lithology and geomorphology on sediment yield are therefore essential for developing measures to effectively control sediment delivery in this region the objective of this study was to investigate the relative importance of lithological and geomorphological factors for sediment yield in 40 selected karst mountainous catchments in southwest china because of the high co dependence of these variables a partial least squares regression plsr model was used to explore the quantitative relationships between annual sediment yield and 30 lithological and geomorphological factors results showed that the lithology and geomorphology were critically important to annual sediment yield and could explain 65 9 of the total variance in sediment yield the dominant lithological and geomorphological factors controlling annual sediment yield were karst coverage drainage density basin relief plane curvature elevation maximum elevation average slope dolomite coverage relative relief and catchment area this importance or these contributions of lithological and geomorphological factors to annual sediment yield provides a good reference for selecting key factors when developing soil erosion models this study yields a greater understanding of the influences of lithology and geomorphology on sediment yield and is helpful for better catchment management in karst regions

the occurrence of obtuse junction angles and changes in channel width below tributaries along the mekong river south east asia classic descriptions of drainage patterns suggest that confluence angle is determined by the shape of the drainage basin unless constraining factors such as the geological structure affect stream flow downstream changes in channel width below tributary junctions have long been associated with tributary inputs of flow and sediment analysis of tributary junction geometry and channel width changes in large rivers and over large reaches is sparse the lower mekong basin exhibits a generally dendritic drainage network despite flowing through a diverse array of geological settings publicly available spot 5 imagery from google earth was used to identify and catalogue junction geometries and downstream changes in channel width below tributary junctions along a 2200 km reach of the mekong river of the 284 junctions identified the majority 66 2 were acute however 12 4 8 were found to be normal 90 and 75 30 were found to be obtuse this latter number is in contrast to previous studies over similar spatial scales which found little evidence of obtuse junctions meander extension of the incoming tributary and deflection of the tributary across bedrock shoulders were found to be the dominant geomorphological causes of obtuse tributary junctions the relationship between the width of the tributary channels and the width of the mainstem upstream and downstream of the confluences was analysed it was observed that over the whole reach a slight narrowing occurred immediately below tributary junctions although the changes themselves were small the slight net narrowing is shown to be statistically significant the observed relationship is shown to vary considerably with geology the geological control suggests that complex factors play important roles in determining changes to channel width across large systems and that simple cause effect relationships do not hold in such complicated geological settings

structural control on drainage network and catchment area geomorphology in the dead sea area an evaluation using remote sensing and geographic information systems in the wadi zerka ma in catchment area jordan the geology of jordan is characterized by fault systems with three major trends 1 nw se the oldest 2 wnw ese and 3 nnw sse the youngest the drainage network of the wadi zerka ma in catchment area located in the middle of the dead sea rift parallels these structural orientations a regional transtensive fault with embedded normal faults bounds the lower and middle part of the catchment area the topographic profile of the zerka ma in river exhibits two major knickpoints where it crosses two major embedded normal faults the second major knickpoint developed as a result of the dramatic lowering of the lisan lake water level a lake that pre dates the dead sea the decreased water level triggered river incision into the clastic sandstone units of wadi zerka ma in we performed a morphotectonic analysis study to investigate how the rock structures control the drainage network and the catchment area geomorphology according to the transverse topographic symmetry factor t the catchment area is highly asymmetric the major basin asymmetry trend is se oriented parallel to the oldest set of fault systems the catchment area displays a convex hypsometric curve indicating a very recent stage in the geomorphologic cycle our study indicates that the lisan lake catchment area shrinkage and structures growth controlled and shaped the wadi zerka ma in catchment area geomorphology the combined use of a geographic information system gis and remote sensing was shown to be very efficient in unraveling the evolution of the drainage network and catchment area geomorphology

on the interpretation of eddy fluxes during a blocking episode abstract using twice daily synoptic charts objectively analyzed at the national meteorological centre horizontal eddy fluxes of temperature and quasi geostrophic potential vorticity are computed for the month of july 1976 when a blocking anticyclone was centered over western europe the local time averaged eddy variance equations are used to provide a dynamical basis for interpreting the spatial pattern of eddy fluxes and their relation to mean gradients it is shown that a rotational non divergent flux can be identified the cross gradient component of which balances the mean flow advection of eddy variance the remaining flux is the dynamically significant one which helps maintain the block and can be understood in terms of a response to sources and sinks of eddy variance

controls on modern tributary junction alluvial fan occurrence and morphology high atlas mountains morocco abstract modern tributary junction alluvial fans cone shaped depositional landforms formed in confined valley settings were analysed from a 20 km long reach of the dades river in the distal part of the fold thrust belt region in the south central high atlas mountains of morocco here a deeply dissected network of ephemeral tributary streams and a perennial trunk drainage characterised by an arid mountain desert climate are configured onto a folded and thrust faulted mesozoic sedimentary sequence out of 186 tributary streams only 29 16 generated alluvial fans at their tributary junctions the fan generating catchments possess higher relief longer lengths lower gradients and larger areas than nonfan generating catchments whilst geologically fan generating catchments are underlain by folded steeply dipping weak bedrock conducive to high sediment yield tributary junction fans are built from debris flow or fluvial processes into open or confined canyon trunk valley settings the proximity of the perennial trunk drainage combined with the valley morphology produces lobate or foreshortened trimmed fan forms analysis of fan area gradient process catchment area relief length gradient and tributary valley width variables reveals weak morphometric relationships highlighted by residual plots that show dominance of smaller and lower gradient than expected fan forms these morphometric relationships can be explained by interplay between the catchment and trunk drainage geology morphology climate and flood regime that are combined into a conceptual build and reset model ephemeral tributary junction fans develop progressively during annual localised winter spring storm events attempting to build towards a morphological equilibrium however the fans never reach an equilibrium morphological form as they are reset by rare 10 year large floods along the river dades that are linked to regional incursions of atlantic low pressure troughs the model highlights the spatial and temporal variability of tributary junction fan building and illustrates the connectivity coupling importance of such features in dryland mountainous terrains

assessment of fractures in some columns inside the crypt of the cattedrale di otranto using integrated geophysical methods we investigate the problem of internal fracturing of the columns of a building of cultural importance the crypt of the cattedrale di otranto apulia italy using a multi disciplinary approach integrating different non destructive techniques microclimatic and geophysical in fact historic buildings over centuries may accumulate a high concentration of water and or moisture that increases significantly the deterioration rate diminishing the mechanical resistance it is well known that the distribution of moisture within stone strongly depends on ambient conditions i e temperature and relative humidity no suitable environmental condition in the crypt and the presence of wet buried structures in the ground involved in the process of deterioration have been indeed assessed in previous surveys actually we perform a ground penetrating radar gpr investigation in reflection mode in order to reveal the existence of fractures inside the columns because of the important rising of water from pavement the reconstruction of the fracture distribution is fundamental to plan the safeguard and the restoration of the columns themselves and also the stability of the crypt and of the uppermost cathedral such survey was performed on seven columns using gpr technique moreover the electrical resistivity tomography ert and gpr traveltime tomography tt methods were applied on the most damaged column the results obtained with these different methodologies are in good agreement however the 2d electrical resistivity tomography seems to be less resolutive than gpr while the gpr traveltime tomography is more time expensive than gpr reflection mode method the gpr method in reflection mode allows to reconstruct the main fractures inside the columns also in virtue of its penetration power we think that the joining of different methodologies permits to better understand the complex physical mechanisms in the phenomenon of deterioration of the cultural heritage in order to achieve useful information for possible future restoration works 2006 elsevier ltd all rights reserved

holocene evolution and geochronology of a semiarid fluvial system in the western slope of the central andes ams 14 c data in el transito river valley northern chile abstract in this paper we discriminate the contribution of the different sediment sources into a river situated in the semiarid region of northern chile differentiating the ones driven by the paraglacial response from the ones yielded to the tributary junction alluvial fans or the ones coming from the hillslopes the sedimentary infilling is accurately described in the main landforms such as alluvial fans alluvial terraces and landslides in the current valley floor where twenty six 14c ams samples were picked up the 14c age data indicate that the aggradation in the uppermost part of the valley immediately postdates the glacial retreat at 15 000 14c years cal b p and spans the whole holocene starting at 11 ka b p and finishing about 2 ka b p the main sources for lateral inputs are debris flows from tributary catchments in the portion where the river is embedded in between 1000 and 2000 m a s l as well as catastrophic landslides additionally an extensive detailed geomorphological mapping is provided to discuss the meaning of the ages together with an assessment of where the samples came from finally the dataset and field criteria provided in this work contribute to better perform paleoclimatological interpretations for the semiarid fluvial systems of northern chile these interpretations usually consider the increased influence of the westerlies during the holocene and the span of time that the paraglacial response delivers glacigenic sediments into the system

meanders of the gulf stream downstream from cape hatteras 1975 1978 abstract weekly gulf stream paths within 1000 km downstream of cape hatteras were obtained for 1975 78 from the navy s weekly eofa charts based on satellite ir imagery they displayed two dominant meander modes first a standing meander energetic over periods between 4 months and at least 4 years and second down stream propagating meanders that were most energetic at periods of several weeks the long period standing meander was confined between nodes located at the separation point near cape hatteras i e where the stream s mean path turns seaward and at a point about 600 km farther downstream the rms amplitude was 36 km at the antinode the amplitude of propagating meanders increased rapidly in the first 200 km downstream of the separation point where the capture of warm core eddies was common farther down stream the predominant meanders had a wavelength averaging 330 km a period averaging 1 5 month a phase speed averaging 8 cm s 1 a downstream group speed averaging 17 cm s 1 and downstrea

the eddy radiation field of the gulf stream as measured by ocean acoustic tomography the gulf stream system is one of the most important components of the north atlantic circulation reciprocal acoustic transmissions have been analyzed to determine the structure and variability of temperature current velocity and relative vorticity in a region just south of the gulf stream observational evidence is presented that the gulf stream is the source of the energetic eddy variability found in the atlantic interior through highly nonlinear processes eddy activity energy radiates away from the stream southward via rossby wave packets

surface sediment characteristics and present dynamics in alluvial fans of the central spanish pyrenees three alluvial fans in the ribera de biescas upper gallego valley and central spanish pyrenees have been studied in order to explain the most recent changes and to identify the spatial organization of the sediment in the alluvial fans surveyed the proximal area is dominated by debris flows which pass downslope into transitional and fluvial deposits the relative importance of each type of sediment is closely related to the size and gradient of the alluvial fan as well as to the gradient in the final stretch of the stream in general the size of the sediment decreases from the proximal to the distal area while the roundness increases nevertheless there are noticeable irregularities in the trend both in longitudinal and transverse transects due mainly to the sedimentary dynamics of the debris flows as they advance towards the inner part of each alluvial fan during the most intense peak flows a sudden shrinkage of the most active area and incision along the fan channels has been assessed and related to land use changes in the catchments

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

the impact of mid depth recirculations on the distribution of tracers in the north atlantic an interesting feature of the waters carried equatorward by the deep western boundary current in the north atlantic is their sharp vertical differentiation in tracer concentration and accordingly tracer age in this work i demonstrate that the strui ture and lateral extent of the recirculations in the intermediate and deep north atlantic have substantive differences with depth that can help explain the observed pattern of transient tracers such as tritium 3he and cfcs while recirculations are present at all depths spanned by the boundary current the distinct tracer minimum occurs at the depth where the recirculation extent is maximized overall the effect of the large scale recirculation at intermediate depths is to lengthen mixing pathways and to provide an alternate route for north atlantic deep waters to enter the subtropical basin

climate and anthropogenic factors affecting alluvial fan development during the late holocene in the central ebro valley northeast spain the late holocene in the central ebro depression is characterized by a number of morphodynamic stages that affected hillslopes and channels climate fluctuations and human activities together caused severe erosion and floods resulting in alternating stages of accumulation and incision in the valley floors seven accumulation levels n6 n0 correlated with ebro river fluvial terraces have been identified in the secondary fluvial network of the central ebro depression the main accumulation level n3 corresponds to a long period of increased hillslope erosion and sedimentation in the valleys from the neolithic to the late roman periods the accumulation levels are evident throughout the valleys and extend to the valley mouths where many connect with alluvial fans the study of several sedimentological profiles 14c ams dating and many archaeological remnants have enabled detailed assessment of sedimentation characteristics in the alluvial fans and the relationship thereof to the presence of human sett

tectonic controls of the north anatolian fault system nafs on the geomorphic evolution of the alluvial fans and fan catchments in erzincan pull apart basin turkey abstract the erzincan pull apart basin is located in the eastern section of the north anatolian fault system nafs the tectonic evolution of this basin is mostly controlled by strike slip master faults of the nafs this study examines the topography structure relationships in an effort to evaluate the tectonic signatures in the landscape paying special attention to recent tectonic activity in the study the main focus is on the tectonic controls of the nafs on the geomorphic evolution of alluvial fans and fan catchments in the erzincan pull apart basin the observations of the amount of tilting of the alluvial fans and its relation with morphometric asymmetry factor af hypsometric integral hi fractal analysis of drainage networks d properties of the fan catchments provide valuable information about the tectonic evolution of the basin area the results of the analyses showed that the alluvial fan and fan catchment morphology in the pull apart basin are mainly controlled by the ongoing tectonic activity of the nafs the fault system in the basin has controlled the accommodation space by causing differential subsidence of the basin and aggradation processes by causing channel migration channel incision and tilting the alluvial fans

lateral erosion toe cutting of alluvial fans by axial rivers implications for basin analysis and architecture abstract we document the neglected phenomenon of lateral erosion toe cutting of alluvial fans by non incising axial river channels field examples from the holocene of the big lost river basin idaho and the plio pleistocene of the rio grande rift new mexico help to establish architectural models with more general application to basin analysis the process of toe cutting can lead to complete fan destruction and may be a response to climate change tectonic tilting fault propagation or a combination of these variables it gives rise to near horizontal erosion surfaces cut in fan sediment steep fan margin scarps progressive up fan incision from the scarp by a network of channels soil formation up fan away from the incised channel network a deposit of axial alluvium that overlies the erosion surface and onlaps the scarp once avulsion occurs to take the axial channel away from the bajada margin distinctive healing wedges of fan alluvium prograde across abandoned axial river channel and floodplain deposits gradually onlapping the eroded scarp and its upstream network of incised channels toe cutting has important stratigraphic basin analysis and economic consequences bajada deposits subject to the process exhibit appreciable extra groundwater and petroleum reservoir potential in the intercalations of more porous and permeable axial fluvial sediments

neotectonic control on drainage systems gis based geomorphometric and morphotectonic assessment for crete greece abstract geomorphic indices can be used to examine the geomorphological and tectonic processes responsible for the development of the drainage basins such indices can be dependent on tectonics erosional processes and other factors that control the morphology of the landforms the inter relationships between geomorphic indices can determine the influence of regional tectonic activity in the shape development of drainage basins a multi criteria decision analysis mcda procedure has been used to perform an integrated cluster analysis that highlights information associated with the dominant regional tectonic activity factor analysis fa and analytical hierarchy process ahp were considered within that procedure producing a representation of the distributed regional tectonic activity of the drainage basins studied the study area is western crete located in the outer fore arc of the hellenic subduction zone one of the world s most tectonically active regions the results indicate that in the landscape evolution of the study area especially the western basins tectonic controls dominate over lithological controls

observed changes in baroclinic wave activity during the life cycles of low frequency circulation anomalies abstract anomalous baroclinic wave activity during the onset and decay of blocking patterns in the northern hemisphere winter is investigated based upon a 30 year record of 500 mb height and sea level pressure a slowly varying envelope function is defined at each gridpoint in order to represent the modulation of the amplitude of baroclinic wave activity by the low frequency circulation anomalies related to blocking the envelope function fields and the low frequency circulation fields are composited relative to the onset and decay times of four persistent dipole patterns in low frequency circulation anomalies located downstream of the climatological mean stormtracks one polarity of the anomaly patterns corresponds to dipole or modon like blocking patterns over the eastern oceans and the other to strong zonal flow patterns each of the eight composites is comprised of more than 50 persistent blocking or zonal flow episodes the most striking common feature observed during the onset of blocking over th

a theoretical treatment of the effect of microscopic fluid distribution on the dielectric properties of partially saturated rocks1 microscopic fluid distribution can have a significant effect on the dielectric properties of partially saturated rocks evidence of this effect is found in the laboratory data presented by knight and nur in which different methods for controlling saturation produced very different results for the dependence of the dielectric response on water saturation in this study previously derived models for the dielectric response of a heterogeneous medium are generalized and the case of a pore space occupied by multiple pore fluids is considered by using various geometrical distributions of water and gas it is observed that both the pore geometry in which saturation conditions are changing and the gas water geometry within a given pore space are critical factors in determining the effective dielectric response of a partially saturated rock as an example data for a tight gas sandstone undergoing a cycle of imbibition and drying are analysed previous research has demonstrated that significantly different microscopic fluid distributions result from the application of these two techniques to control the level of water saturation by approximating these microscopic fluid distributions using simple geometrical models good agreement is found between experimental data and calculated dielectric properties

the role of high and low frequency dynamics in blocking formation time evolutions of prominent blocking flow configurations over the north pacific and europe are compared based upon composites for the 30 strongest events observed during 27 recent winter seasons fluctuations associated with synoptic scale migratory eddies have been filtered out before the compositing a quasi stationary wave train across the atlantic is evident during the blocking amplification over europe while no counterpart is found to the west of the amplifying blocking over the north pacific correlation between the tropopause level potential vorticity pv and meridional wind velocity associated with the amplifying blocking is found to be negative over europe in association with the anticyclonic evolution of the low pv center but it is almost zero over the north pacific feedback from the synoptic scale eddies as evaluated in the form of 250 mb geopotential height tendency due to the eddy vorticity flux convergence accounts for more than 75 of the observed amplification for the pacific blocking and less than 45 for the european blocking this difference is highlighted in two types of contour advection with surgery experiments in one of them pv contours observed four days before the peak blocking time were advected by composite time series of the low pass filtered observational wind and in the other experiment they were advected by the low pass filtered wind from which the transient eddy feedback evaluated as above had been removed at every time step hence the latter data should be dominated by low frequency dynamics for the european blocking both experiments can reproduce the anticyclonic evolution of low pv air within a blocking ridge as observed for the pacific blocking in contrast the observed intrusion of low pv air into the higher latitudes cannot be reproduced without the transient feedback furthermore in a barotropic model initialized with the composite 250 mb flow observed three days before the peak time a simulated blocking development over the north pacific is more sensitive to the insertion of the observed transient feedback than that over europe these results suggest that the incoming wave activity flux associated with a quasi stationary rossby wave train is of primary importance in the blocking formation over europe whereas the forcing by the synoptic scale transients is indispensable to that over the north pacific

quantifying long term catchment changes of alluvial fan systems in mountain areas affected by uplift significant reorganization of drainage networks can occur through river capture this modification can dramatically affect sediment flux and routing into adjacent sedimentary basins it is thus important to obtain information on rates and direction of changes in catchment areas in such environments this can be achieved where the original precapture catchments can be compared with the postcapture scenario this paper examines three modern mountain catchments from southeast spain that were affected by river capture and that fed relict pliocene pleistocene alluvial fan systems morphometric data have been collated for complete quaternary mountain catchment piedmont fan systems these data are used to establish regressions to determine catchment area and basin relief from a combination of fan characteristics area and gradient these relationships are then used to predict the original catchment characteristics for the three pliocene pleistocene relict fans and compared with the modern catchments to quantify the magnitude and direction of changes which have affected the drainage basins since fan abandonment in the early pleistocene the figures suggest that the catchment areas are responding to regional uplift most significantly by drainage net expansion facilitated by river capture rather than lowering of surface relief as a result sediment routing into the sedimentary basins has been radically altered

diagnoses of an eddy resolving atlantic ocean model simulation in the vicinity of the gulf stream part i potential vorticity abstract output of an eddy resolving model of the north atlantic is diagnosed in the vicinity of the gulf stream gs using quasigeostrophic potential vorticity qgpv ertel s potential vorticity pv and particle trajectories time series of qgpv show strong input of qgpv by the gs in the top 1000 m of the model ocean vigorous wave motions are observed in the vicinity of the model gs mixing qgpv in the region the time mean horizontal qgpv structures show qualitative similarity to those of large scale climatological pv calculated from hydrographic data by keffer and that of lozier the top 1000 m of the model ocean is characterized by a tongue or an elongated island of high mean qgpv along the gs it is demonstrated that the tongue is a product of strong qgpv input by the gs vigorous mixing by eddies and dissipation of qgpv along the path of the gs at the intermediate depths 1000 2500 m a large region of nearly homogenized mean pv or weakly varying mean qgpv is found to the west of the mid atla

diagnoses of an eddy resolving atlantic ocean model simulation in the vicinity of the gulf stream part ii eddy potential enstrophy and eddy potential vorticity fluxes abstract output of an eddy resolving model of the north atlantic is diagnosed in the vicinity of the gulf stream gs using quasigeostrophic potential vorticity qgpv quasigeostrophic potential enstrophy qgpe and modified divergent eddy potential vorticity flux v hq d a tongue or an elongated island of large mean qgpv along the model gs in the top 1000 m is associated with predominantly downgradient v hq d suggesting that the horizontal eddy fluxes are balancing a sink of eddy qgpe in most of the tongue or island by converting the mean qgpe into eddy qgpe some large upgradient v hq d is observed to the north of the center of the tongue or island however suggesting that some of the eddy fluxes in the northern half of the tongue or island of high qgpv are balancing a source of eddy qgpe there by converting eddy qgpe into the mean qgpe at the intermediate levels of the model under the gs eddy qgpe is small and the role of eddies appears to be mixed they are forcing the mean to some

controls on modern alluvial fan processes in the central alps northern italy alluvial fan development in alpine areas is often affected by catastrophic sedimentary processes associated with extreme oods events causing serious risks for people living on the fans hazard assessment in these areas depends on proper identi cation of the dominant sedimentary processes on the fans data from a set of 209 alluvial fans from the central alps of italy are presented in this paper and analysed with the help of various statistical techniques linear regression principal components analysis cluster analysis discriminant analysis and logistic regression first we used modern sedimentary facies and historical records ood events since 15th century to distinguish between the two dominant sedimentary processes on alluvial fans debris ows and stream ows then in order to analyse the main controls on past and present fan processes 36 morphological geological and land use variables were analysed as with observations for arid environment fans catchment morphology is the most in uential factor in the study area whereas geology and land use are minor controls the role of climatic change and landsliding within the catchments also seems to be very important and is discussed statistical techniques also help in differentiating groups of alluvial fans by sets of controlling factors including stage and type of evolution finally by using discriminant analysis and logistic regression we classi ed alluvial fans according to the dominant sedimentary process with a success rate ranging between 75 and 92 per cent copyright 2004 john wiley sons ltd

fire related debris flows in the iberian range spain abstract debris flows occurred three weeks after a wildfire in august 1986 in the najerilla river valley in the iberian range northern spain the flows were triggered by a brief intense rainstorm approximately 25 mm h 1 over 15 min in a small area with steep slopes covered by a thick colluvium of quartzite clasts this storm resulted in the development of several unconfined hillslope debris flows and the formation of an alluvial fan at the mouth of the pitare stream which partially blocked the najerilla river we analysed the conditions that led to the development of the debris flows and estimated the rainfall threshold for the debris flows to occur as well as the total volume of mobilised sediment four factors contributed to the debris flows i the occurrence of a rainstorm three weeks after a wildfire which had removed the plant cover from the soil ii the steep slopes in the area 30 which were the most affected by debris flows iii the presence of quartzite scarps on the hillslopes which favoured the development of a firehose effect involving channelised surface runoff and iv the low plasticity index values of the fine material of the colluvium indices of 7 to 8 which enabled rapid liquefaction estimates of rainfall intensity derived from the estimated peak flow in the pitare stream suggests that around 80 mm of rainfall fell in approximately 15 min although this is clearly an overestimated value given the high proportion of sediment load transported during the peak flow various equations estimated a rainfall threshold of approximately 25 mm h 1 considering a concentration time of 15 min the total sediment transported by the debris flows was 10 500 m3 15 750 mg 6800 mg km 2 and the pitare stream alone transported a minimum of 4000 m3 6000 mg 2500 mg km 2 these results suggest that the rainfall threshold for initiating debris flows decreases following a wildfire such that an ordinary rainstorm is able to trigger a severe erosion and sediment transport event given the absence of fresh landslide scars on the hillslopes the origin of the fire related debris flows in the najerilla river valley appears to have been directly linked to increased rates of overland flow having a greater effect than infiltration for triggering debris flows

underlying issues on the selection use and conservation of building limestone an argument is presented that despite popular assumptions many limestones especially the wide range of clastic and in general granular limestones do not decay in a steady and predictable pattern in response to slow dissolution instead these stones especially when used in construction in polluted environments invariably decay episodically through physical breakdown most commonly this is accomplished through a variety of salt weathering mechanisms that if unconstrained can lead to the rapid catastrophic decay of building blocks and their complete loss a process that has driven the extensive programmes of stone replacement that are typical of buildings constructed of these stones in polluted environments especially those rich in sulphur and particulates the most common constraint on accelerated decay has been the rapid development of gypsum crusts that for example could rapidly heal the scars left by contour scaling it is ironic therefore that any reduction in pollution could conceivably lead to increased erosion by retarding this healing process because of this temporal variability of decay and its translation into spatial complexity it is important that further research is undertaken to understand controls on the decay of these important building stones so that future conservation strategies can be appropriately informed on the predictability of decay and the role

hydraulic characterization of river networks based on flow patterns simulated by 2 d shallow water modeling scaling properties multifractal interpretation and perspectives for channel heads detection

tributary development along winding streams and valleys causal model for the percentage of trans links trans along such streams analyses of 40 stream reaches indicate 1 that 81 percent of the variation in the percentage of tributaries on the concave side outside of bends cvt can be explained by the mean number of tributaries per bend n t valley sinuosity p and the rate of bend migration and 2 that 72 percent of the variation in trans can be accounted for by cvt n t and p the variable n t represents both the availability of space on the convex inside of bends relative to that required for a tributary to form and the ratio of the mean bend length to mean chain length which affects the convergence and divergence of runoff down valley sides locations of tributaries along main streams can be understood largely in terms of four factors spatial requirements of tributaries sinuosity of the main valley lengths of the valley bends and rate of bend migration modified journal abstract

eddy mean flow interaction in the gulf stream at 68 w part i eddy energetics abstract from june 1988 to august 1990 twelve tall high performance current meter moorings measured the gulf stream s velocity and temperature fields at nominal depths of 400 m 700 m 1000 m and 3500 m along three lines centered at 68 w the overall eddy variability during the 26 month experiment was dominated by six large amplitude trough formation events with each event lasting approximately one month to determine the source s of energy for this eddy variability the eddy energy budget is evaluated traditionally the baroclinic conversion of mean potential energy to eddy potential energy is defined as a downgradient heat flux however because a nondivergent heat flux can be downgradient even under conditions in which there is no barolinic conversion occurring a better more dynamically correct definition of a baroclinic conversion rate is a downgradient horizontally divergent heat flux the horizontally divergent heat flux component is estimated to be approximately half the full horizontal hea

headwater stream length dynamics across four physiographic provinces of the appalachian highlands understanding patterns of expansion contraction and disconnection of headwater stream length in diverse settings is invaluable for the effective management of water resources as well as for informing research in the hydrology ecology and biogeochemistry of temporary streams more accurate mapping of the stream network and quantitative measures of flow duration in the vast headwater regions facilitate implementation of water quality regulation and other policies to protect waterways we determined the length and connectivity of the wet stream and geomorphic channel network in three forested catchments 90 of the mean daily discharge stream network dynamics reflected geologic controls at both regional and local scales wet stream length was most variable at two valley and ridge catchments on a shale scarp slope and changed the least in the blue ridge the density and source area of flow origins differed between the crystalline and sedimentary physiographic provinces as the appalachian plateau and valley and ridge had fewer origins with much larger contributing areas than new england and the blue ridge however the length and surface connectivity of the wet stream depended on local lithology geologic structure and the distribution of surficial deposits such as boulders glacially derived material and colluival debris or sediment valley fills several proxies indicate the magnitude of stream length dynamics including bankfull channel width network connectivity the base flow index and the ratio of geomorphic channel to wet stream length consideration of geologic characteristics at multiple spatial scales is imperative for future investigations of flow intermittency in headwaters

drainage network structure and the diameter magnitude relation drainage network structure can be described in terms of elongation or compaction by using the network diameter and magnitude the relation between network diameter and magnitude is the topologic equivalent of the well known relationship between mainstream length and drainage basin area diameter increases with magnitude but at a decreasing rate as networks are sampled over a greater size range downstream variations in river network structure reflect regional geomorphic environment erosional history and space filling by tributaries of different sizes the sequence of tributary magnitudes down a mainstream is not random large tributaries preempt drainage area and tend to be followed downstream by a number of small tributaries in fluvial landscapes free from geological constraints river networks tend to become relatively more elongate in structure with increasing size downstream

tributary junction fans of china s yangtze three gorges valley morphological implications abstract the tributary junctions to main rivers within incised canyons reflect the relationships between stream power and sediment fed to the main river by tributary tributary junctions within the three gorges valley of the yangtze river china were classified into 7 types on the basis of the presence or absence of tributary junction fans and the size and style of the fans three reaches totaling 180 km in length were mapped in the field and for a sample of 120 tributary junctions morphometric properties of the feeder catchments were derived small steep tributaries do not generate tributary junction fans nor do the largest tributaries for intermediate sized tributary catchments of approximately 1 30 km2 threshold conditions can be identified between the relatively steep more deeply dissected catchments mean basin slope approximately 0 1 relief range approximately 250 800 m that generate large tributary junction fans and less steep less deeply dissected catchments mean basin slope

sedimentary processes vertical stratification sequences and geomorphology of the roaring river alluvial fan rocky mountain national park colorado abstract the roaring river alluvial fan formed on 15 july 1982 in rocky mountain national park colorado by a catastrophic flood that was generated by a dam failure the fan covers an area of 0 25 square km has a radial length of 0 7 km and is up to 14 m thick sedimentation occurred in three phases each producing a distinct fan lobe initial sedimentation was by a noncohesive sediment gravity flow which deposited two levees on the proximal boundaries of lobe i the levees consist of a poorly sorted mixture of logs sand pebbles cobbles and boulders the first two lobes were built primarily by sheetflooding which deposited imbricated boulders in trains behind obstacles that formed as jams between boulders or logs and upright trees horizontally laminated granule and sand sedimentation took place down fan from the boulders due to deceleration of the expanding sheetflood thin to medium interbedded sand and cobble pebble gravel couplets were deposited by sheetflooding on the third lobe gravel was transported as bedload by supercritical flow and deposited locally where antidunes broke sand was transported as suspended load and deposited where flood velocity locally decreased due to destruction of antidunes increased roughness or flow separation around the low amplitude gravel bed forms the flood rechannelized at the distal end of lobe iii due to constriction between the fan and the valley margin deposits in the upper rechannelized reaches consist of crudely bedded cobble and pebble gravel and interstratified pebble gravel and backset bedded sand deposition was by supercritical flow in the lower reaches planar cross bedded sandy pebble gravel and climbing ripple horizontal trough cross bedded and backset bedded sand were deposited by supercritical and subcritical flow the flood deposit was modified during waning flood stage and during the three years following the flood by noncatastrophic discharge events these events formed braided distributary channels by erosion into the top of the sheet flood deposits fan building took place mostly by catastrophic unconfined discharge whereas much of the present fan surface consists of braided channels that formed by erosion into the sheetflood deposits by noncatastrophic discharge

morphotectonic analysis of aripal basin in the north western himalayas india an evaluation of tectonics derived from geomorphic indices abstract himalayan river basins are exposed to continuous erosion and deformational processes the main goal of this paper is to characterize the tectonic activity as it acts as a controlling factor in the development of landforms in the tectonically active terrains research was carried out in the aripal basin which lies to the south east of kashmir valley one of the right bank tributary of river jhelum the geomorphic indices and morphometric parameters are determined using advanced spaceborne thermal reflection and emission radiometer aster 30 m digital elevation model the low mountain front sinuosity smf 1 3 s type hypsometric curve with high hypsometric integral hi 0 35 low valley floor width to valley height ratios vf

controls on modern fan morphology in calabria southern italy abstract alluvial fans are widespread throughout calabria but only a minority display evidence of current activity in order to understand if and to what extent fan types and their morphology are dependent on the physical environment including characteristics and processes of the depositional site and drainage basin we performed a series of discriminant analyses these analyses used as classification factors the presence or absence of fill in the feeder channel conditions of confinement by host terrain the dominant depositional process debris flow or sheetflood and morphometric attributes of fans and drainage basins as the discriminant function variables in general fan slope area and width length ratio and for basins melton s ruggedness number and source ratio were the most useful variables for classification best results were obtained by discriminating the types of fan deposits and the presence versus absence of fill in the feeder channel if the feeder source is singular fan morphology is controlled by constructional processes and is tightly linked to basin morphology on the other hand fan and basin morphology are also strongly dependent on the rock mechanical characteristics with hard rocks imparting to the basin a high ruggedness and to fans a high gradient larger fans however are those where sheetflooding predominates results of discriminant analysis based on fan and basin variables are much more significant than those based on fan variables only this means that the differences between characteristics of fan and basin systems are better defined than those between characteristics of fans only

geological controls on the topological properties of some trellis channel networks it has been traditionally assumed but never quantitatively demonstrated that the topological properties of trellis channel networks are strongly influenced by the underlying geology in this study the topological properties of seven trellis networks underlain by a plunging syncline are analyzed and compared with those of 45 dendritic networks the analysis of the trellis networks reveals 1 that tributaries flowing both downplunge and downdip are preferentially developed 2 that there is an excess of obtuse over acute tributaries and chains because the general alignment of the networks is such that most of the tributaries flowing downplunge are obtuse 3 that cis links outnumber trans links as far downstream as diameter 7 links owing to the preferential development of tributaries flowing downdip 4 that because the spacing of along strike streams and ridges constrains the development of across strike tributaries there are strong spatial regularities in tributary size and 5 that for the same reason the trellis networks contain a higher proportion of small tributaries and a lower proportion of large tributaries than do dendritic networks thus this study not only establishes that geological controls have a pronounced effect on the topological properties of trellis networks but it shows how particular topological properties are affected by specific controls as these controls vary from one area of trellis drainage to another the topological properties of the channel networks might also be expected to vary consequently no one set of topological properties can be considered typical of trellis networks

nonlinear dynamical systems in geomorphology revolution or evolution abstract geomorphic systems typically exhibit complex apparently random behaviors and patterns in both spatial and temporal domains this complexity can arise from the cumulative impacts of individual process response mechanisms which are far too numerous to be accounted for in individual detail or due to multiple controls over process response relationships which operate over a range of spatial and temporal scales stochastic complexity nonlinear dynamical systems nds theory which includes specific techniques and concepts such as chaos dissipative structures bifurcation and catastrophe theory and fractals shows that extreme complexity can also arise due to the nonlinear dynamics and couplings of relatively simple systems represented by relatively small equation systems deterministic complexity while emphasis in earth science has been largely on stochastic complexity geomorphologists have long recognized the presence of deterministic complexity as well recent developments in the study of nonlinear dynamical systems have implications for the ability to make reliable long term predictions and therefore applications of nds in geomorphology may be revolutionary to some extent however virtually all the basic conceptual underpinnings of nds theory can be mapped onto existing and even traditional theoretical concepts in geomorphology in this sense the use of nds concepts in understanding earth surface processes and landforms is evolutionary the link between traditional and nds based concepts is illustrated by analyzing a generalized geomorphic mass flux system it is shown that the system is in most cases unstable consistent with chaos or deterministic complexity however the three attractor states of the system correspond exactly to the states of aggradation degradation and steady state

gulf stream path and thermocline structure near 74 w and 68 w the synoptic ocean prediction synop experiment had the goal of providing a physical understanding of energetic mesoscale eddy processes in the gulf stream in the synop inlet array off cape hatteras and in the central array near 68 w modred observations were collected from october 1987 through august 1990 the inlet array measured the surface path and bottom currents where the gulf stream leaves the continental margin to enter the deep water regime small amplitude propagating and growing meanders characterized the variability there the central array measured velocity and temperature as a proxy for density at four levels in the water column as well as the upper and deep level streamfunctions all with mesoscale resolution near 70 w the path envelope exhibited a relative node confined within a 40 km band 55 of the time near 68 w the path envelope was over 3 times as wide due to several elongated steep meander troughs and relatively steep meander crests the crests typically propagated downstream without much growth the troughs often stalled near 68 w steepened and persisted for one to several months two cases evolved into s shaped paths and subsequently formed rings even the time averaged fields showed a small trough in the mean path and thermocline structure whereas meanders of 20 to 60 day periods had similar spectral levels throughout 70 67 w meanders with long periods 85 day accounted for the local minimum in variance at 70 w bottom pressure and velocity observations revealed repeated periods of intense swirl speeds 0 30 m s 1 abyssal eddies the time averaged deep currents exhibited a mean cyclone centered 30 km offshore and downstream of the upper layer mean trough the cross stream slope of the thermocline steepened linearly with path curvature consistent with gradient wind balance structures are illustrated in the mapped fields consistent with baroclinic instability wherein troughs steepen and rings form

the coupling status of alluvial fans and debris cones a review and synthesis alluvial fans and debris cones link two zones of the fluvial system e g hillslope gully systems to stream channels mountain catchment sediment source areas to main river systems or to sedimentary basins and therefore have important coupling or buffering roles these roles may be both functional and preservational the functional role includes debris cone coupling which controls sediment supply from hillslope gully systems to stream channels influencing channel morphology coupling through larger alluvial fans expressed by fanhead trenching causes a distal shift in sedimentation zones or when expressed by through fan trenching causes complete sediment by pass the preservational role stems from the fact that fans and cones are temporary sediment storage zones and may preserve a record of source area environmental change more sensitively than would sediments preserved further downsystem fan coupling mechanisms include distally induced coupling basal scour toe cutting marginal incision and proximally induced coupling fanhead and midfan trenching these mechanisms lead initially to partial coupling either extending the immediate sediment source area to the stream system or shifting the focus of sedimentation distally complete coupling involves transmission of sediment from the feeder catchment through the fan environment into the downstream drainage or a sedimentary basin the implications of coupling relate to downstream channel response fan morphology sedimentation patterns and vertical sedimentary sequences temporal and spatial scales of coupling are related and with increasing scales the dominant controls shift from storm events to land cover to climatic and base level change and ultimately to the relationships between tectonics and accommodation space finally future research challenges are identified modern dating techniques and sophisticated analysis of remotely sensed data can greatly improve our understanding of fan dynamics and should lead to better cross scale integration between short term process based approaches and long term sedimentological applications while maintaining high quality field based observations copyright 2011 john wiley sons ltd

a multi method investigation of temperature moisture and salt dynamics in tafoni tafraoute morocco despite numerous investigations and theoretical models tafoni weathering is still not fully understood largely because of limited data available on temperature moisture and salt regimes we investigated tafoni developed in granite in the tafraoute region morocco through an exploratory two week multi method field campaign temperatures were measured with ibuttons and by means of infrared thermography moisture distribution and progress were captured with handheld moisture sensors and with drilled in ibuttons salts were analysed in drill dust samples from different positions and rock depths the results derived from very different techniques mutually support one another salts and moisture are concentrated near the base of the investigated tafoni probably due to a saturated pore water body around the base of rock tors salts are accumulated close to the rock surface in tafoni but not on the surrounding rock surfaces a clear correlation was found between moisture and salt contents within a tafone areas of higher humidity also display increased salt concentration near the surface the temperature humidity records allied with ionic analyses suggest that sodium sulfate dominates and is likely to undergo frequent phase changes from thenardite to mirabilite and vice versa two pathways of salt transport in and around tafoni are assumed based on the data infiltration with rainfall on the top and around tors and boulders and capillary rise from saturated pore water bodies to the surface copyright 2015 john wiley sons ltd

inception of channelization and drainage basin formation upstream driven theory the ubiquitous presence of river drainage basins in the terrestrial environment suggests that distributed overland flow generated by rainfall tends to spontaneously organize itself into dendritic systems of discrete channels several recent numerical models describe the evolution of complete drainage basins from the initial condition of rainfall on a flat tilted plateau the surface of which has been provided with random elevation perturbations these analyses model overland flow via the assumption of a perfect balance between gravitational and frictional terms i e in terms of normal flow linear stability analysis applied to the normal flow model has been shown however to fail to select a wavelength corresponding to a finite distance of separation between incipient basins this suggests that the normal flow model may not be a sufficient basis for studying drainage basin development especially at the finest scales of morphologic significance here the concept of a threshold condition for bed erosion is combined with an analysis of the full equations of shallow overland flow in order to study wavelength selection classical linear stability analysis is shown to be inadequate to analyse the problem at the level of inception an alternative linear analysis of bed perturbations based on the threshold condition is developed and shown to lead to the selection of finite wavelength of the correct order of magnitude the analysis here is driven from the upstream direction in that bed erosion is first caused only when sufficient flow has gathered from upstream due to rainfall a downstream driven theory of incipient channelization that is not necessarily dependent upon rainfall is presented in izumi 1993 and is presently in preparation for publication

environmental controls on the evolution of alluvial fans in buena vista valley north central nevada during late quaternary time abstract alluvial fans in buena vista valley north central nevada formed during at least four time periods during the late quaternary as evidenced by four temporally and spatially constrained fan deposits qf1 qf2 qf3 and qf4 from oldest to youngest the stratigraphic relation between qf3 and remnant beach ridge deposits of pluvial lake lahontan the latter of which forms a paleoclimatic proxy for this region indicate that climate and climatic change are primary controls on the evolution of fans qf3 deposition commenced during or immediately following the highstand of lake lahontan between 13 5 and 12 5 ka and continued as lake levels plummeted to levels below the sill elevation of the buena vista subbasin we interpret qf3 to be the result of a dynamic interplay between hillslope vegetation soils and hydrology as they are conditioned by climate and climatic change accelerated pedogenesis because of aerosolic silts and clays from exposed lake sediments coupled with decreased density of vegetation reduced infiltration capacity of the hillslope soils in interscrub areas in contrast to fans in more arid climates the increased runoff was not associated with increased coarse grained sediment yield and major fan aggradation discharge from sediment deficient basins entrenched older proximal fan deposits and transported the sediment downfan to form secondary fans the process response of qf3 to climatic change in north central nevada is especially illustrative of the impact of climate on landscapes in that 1 it results from changes in basin sediment and or water yield that occur in less than 500 years and 2 it differs from responses in arid climates to the south and more semiarid climates to the north the magnitude of vegetation change including type and density of vegetation and the relative proportion of interscrub area is particularly critical to water and sediment yield unit qf2 an early late pleistocene deposit may also have been deposited during a transition from a wetter to drier climate the synchronism of aggradation stability and entrenchment on all fans along the perimeter of buena vista valley in the late quaternary is further support for the dominance of climatic control on fan process on the other hand the impact of other extrinsic variables on fan process including tectonism base level and basin lithology all of which vary along the perimeter is negligible

sedimentologic and geomorphic variations in storm generated alluvial fans howgill fells northwest england in june 1982 a storm with a return period greater than 100 yr but lasting less than 2 5 hr destabilized hillslopes and produced a suite of geomorphologically and sedimentologically diverse alluvial fans thirteen major fans were deposited at the tributary junctions between small 2 catchments and two north flowing headwater streams of the river lune northwest england storm generated fans spread over or became inset into older stable fans and produced localized vertical accretion of as much as 3 m and lateral accretion of as much as 100 m sedimentary processes operating during deposition involved debris flow transitional flow and streamflow six facies types are recognized on the basis of depositional topography sedimentary texture and fabric and matrix content viscous debris flow d1 dilute debris flow d2 transitional flow t1 fluvial bars and lobes s1 s2 and fluvial sheet gravels s3 regionally streamflow deposition prevails over debris flow deposition and type s3 facies has the greatest areal extent temporal and spatial variations in facies deposition during the storm however resulted from water sediment ratio variations fan deposition involved an early phase of debris flow to transitional flow due to large inputs of sediment from hillslope failures this was followed by a systematic change to more dilute conditions resulting in streamflow deposition and eventually in channel incision a significant amount of geomorphic work and complex variations in sedimentary processes during the storm resulted in part from extensive overland flow and hillslope destabilization discriminant analyses indicate that catchment size channel gradient and percentage of area eroded during the storm controlled whether debris flow or streamflow facies dominated a fan sequence smaller steeper catchments had a greater percentage of the area yielding sediment and are dominanted by debris flows whereas larger catchments produced more runoff resulting in dilution and streamflow the results indicate that the facies sequences and fan entrenchment in the howgill fells which are typically considered products of longer term climatic change or tectonics in other localities are here primarily affected by thresholds related to catchment geomorphology by the type of sediment available and by the position within the storm cell

laws place history and the interpretation of landforms the state of an earth surface system ess is determined by three sets of factors laws place and history laws l l1 l2 ln are the n general principles applicable to any such system at any time place factors p p1 p2 pm are the m relevant characteristics of the local or regional environment history factors h h1 h2 hq include the previous evolutionary pathway of the ess its stage of development past disturbance and initial conditions geoscience investigation may focus on laws place or history but ultimately all three are necessary to understand and explain ess the lph triad is useful as a pedagogical device illustrated here via application to explaining the world s longest cave mammoth cave ky beyond providing a useful checklist the lph framework provides analytical traction to some difficult research problems for example studies of the avulsions of three southeast texas rivers showed substantial differences in avulsion regimes and resulting alluvial morphology despite the proximity and superficial similarity of the systems avulsions are governed by the same laws in all cases l a l b l c and the three rivers have undergone the same sea level climate and tectonic histories as well as the same general anthropic impacts h a h b h c though regional environmental controls are similar local details such as the location of the modern main channel relative to pleistocene meander channels differ and thus these place factors explain the differences between the rivers the lph framework or similar types of reasoning is implicit in many types of geoscience analysis explicit attention to the triad can help solve or address many specific problems and remind us of the importance of all three sets of factors copyright 2016 john wiley sons ltd

revisiting scaling laws in river basins new considerations across hillslope and fluvial regimes 1 increasing availability of high resolution 1 m topography data and enhanced computational processing power present new opportunities to study landscape organization at a detail not possible before here we propose the use of directed distance from the divide as the scale parameter instead of horton s stream order or upstream contributing area for performing detailed probabilistic analysis of landscapes over a broad range of scales this scale parameter offers several advantages for applications in hydrology geomorphology and ecology in that it can be directly related to length scale dependent processes it can be applied seamlessly across the hillslope and fluvial regimes and it is a continuous parameter allowing accurate statistical characterization higher order statistical moments across scales application of this scaling formalism to three basins in california demonstrates the emergence of three distinct geomorphic regimes of divergent highly convergent and moderately convergent fluvial pathways with notable differences in their scaling relationships and in the variability or spatial heterogeneity of topographic attributes in each regime we show that topographic attributes such as slopes and curvatures conditional on directed distance from the divide exhibit less variability than those same attributes conditional on upstream contributing area thus affording a sharper identification of regime transitions and increased accuracy in the scaling analysis

landslide locations and drainage network development a case study of hong kong abstract landslides are one of the most dominant geomorphic processes that affect humid tropical environments previous studies in hong kong were mainly focused on spatial and temporal relationships between landslide distribution and the potential controlling factors using geographical information systems gis few natural landslide studies have examined the geomorphological aspects regarding the drainage network development at a basin scale this research examined landslide locations with reference to theories of fluvial drainage development eight small drainage basins 5 31 km2 were studied in which 451 landslides were recorded results have shown that landslide locations are related to a headward progression of the drainage network integration starting from the mainstream the fifth order up to the first order tributaries indicated by the systematic variation between morphometric parameters and landslide density

mechanism for low frequency variability and salt flux in the mediterranean salt tongue the role of baroclinic instability in the generation of low frequency variability in the interior of ocean subtropical gyres and its possible importance in the zonal flux of salt and heat within the mediterranean salt tongue are discussed the observed zonal enhancement of the low frequency variability is interpreted as the signature of baroclinic instability of the large scale wind driven flow the zonal orientation results from the relatively weak vertical shear of the large scale upper ocean flow and the stabilizing influence of the planetary vorticity gradient there is a reversal in the vertical shear of velocity at middepths in the eastern basin of the north atlantic that results in a local middepth maximum in the zonal eddy flux of density linear theory predicts a vertical structure of this density flux that is nearly coincident with the observed vertical distribution of the warm salty water of the mediterranean salt tongue a primitive equation model is used to investigate the nonlinear large amplitude regime the zonal eddy density or salt flux averaged over several wavelengths and several cycles of wave growth and breaking indicates that this mechanism may be an important component in the overall salt balance in this region