hydrological and post depositional impacts on the distribution of holocene archaeological sites the case of the holocene middle rhone river basin france on a landscape scale the location of archaeological sites strongly influences their potential for preservation the recent progress made in the acquired knowledge of the rhone river basin palaeodynamics occurring simultaneously to the development of intensive rescue archaeological surveys on fluvial plains provides information on the burying and post depositional processes of archaeological records for all of the holocene cultural phases even if the lowlands have traditionally been seen as having lower population densities and are dominated by late holocene sediments the systematic exploration of the soil archives has revealed that the archaeological potential was concentrated in the lower alluvial plains and the alpine foothill river fans the taphonomic corrections and correlative predictive model carried out under gis have changed our perception of the settlement history of the northwestern mediterranean region they put in doubt some initial settlement patterns some chronocultural hiatuses based on preconceived models of land use especially for the first neolithic and the protohistoric periods

paleofloods and ancient fishing weirs in nw iberian rivers a 15 m thick fluvial sedimentary record of the nw iberian lower mino river was studied grain size analyses were performed and twelve samples were dated using optically stimulated luminescence dating techniques documenting a 1300 yr old reconstructed fluvial record that does not match with known climate fluctuations in the area but is linked instead to the construction of a series of ancient fishing weirs pesqueiras the sedimentation phases are in agreement with known episodes of increased population density which suggests active use of the pesqueiras a number of sedimentation hiatuses in the fluvial record point towards damage to the pesqueiras during large scale flooding in the mino river basin and a sudden drop in population probably due to the arrival of the plague in the 13th century ad the oldest sedimentation phases started just after 700 ad and we infer that the first pesqueiras were constructed around this time this timing coincides with the transition of the nw iberian landscape towards a more intensively used agricultural landscape as evidenced from other geo archeological investigations the results demonstrate that the pesqueiras are several hundreds of years older than known from historical records but not so old as to date back to the roman occupation

lateglacial and late holocene environmental and vegetational change in salada mediana central ebro basin spain the salada mediana lacustrine sequence central ebro basin spain 41330 10an 0344 w 350 m a s l provides an example of the potential and limitations of saline lake records as palaeoclimate proxies in the semi arid mediterranean region sedimentary facies analyses chemical stratigraphy stable isotopes d18o and d13c of authigenic carbonates d13c values of bulk organic matter and pollen analyses from sediment cores provide paleohydrological and vegetation change reconstructions for the lateglacial and late holocene in the central ebro basin a preliminary chronology is based on 210pb and 14c ams dates the lacustrine sequence is composed of three sedimentary sections the lower section was deposited in a permanent saline to brackish lake this stage represents the most humid period in the record and it was accompanied by the expansion of temperate trees particularly corylus the middle section was deposited in an ephemeral playa lake complex frequent subaerial exposure conditions favour the colonisation of the playa lake oor by chenopodiaceae during a low water table period this interval re ects the most arid conditions in the salada mediana record including the current environment a secondary temperate tree expansion occurred after the maximum aridity period aquatic plants and cyanobacterial mats spread in the lake during periods of raised water tables this paleohydrological and vegetational evolution attests to large changes in e ective moisture during the lateglacial in the semi arid northeastern spain the abundance of corylus during the lateglacial indicates that refugia for temperate trees were located along the ebro valley during the last glacial maximum the holocene sediments in the salada mediana records have been eroded and the upper section represents deposition during the last few centuries 2000 elsevier science ltd and inqua all rights reserved

sediment transport during recent cave flooding events and characterization of speleothem archives of past flooding abstract extreme precipitation events have a disproportionate impact on landscape evolution and on human constructions and the frequency and intensity of extreme events may vary with changes in mean climate in the past and in the future we document the potential for cave sediment archives to record past changes in the frequency of flooding events by characterizing the modern processes responsible for sediment deposition and mobilization during floods and linking these to their incorporation in speleothem deposits we focus on the cueva fria cave system in nw spain which like other caves in the region features abundant sandy sediments sourced from dominant sandstone lithologies in the catchment area in this case delineated by our dye trace study in this system the extreme flood conditions in june 2010 caused overflow of the cave stream and deposition of nearly 1 m of sand in sectors near the cave stream and resulted in burial of some stalagmites in 30 cm of sand in more distal sectors all sectioned stalagmites growing

hydrological reconstruction of holocene paleofloods in baoji tianshui gorge upper weihe river basin china abstract a detailed field study was conducted on the palaeoflood deposit profile in the baoji tianshui gorge in the upper weihe river the sequence of palaeoflood events was established through field observation and grain size analysis with chronological supports from optical stimulated luminescence osl dates and from archaeologically constrained age frameworks the paleoflood peak water level and peak discharge were reconstructed using the pinch out elevation method and the thickness sediment content relationship the results show that three large scale paleoflood events occurred during a period of 3200 3000 yr bp in the baoji tianshui gorge upper weihe river the peak water levels varied between 660 48 and 661 40 m and the peak discharge varied between 23 200 and 25 200 m3 s among the three large scale paleoflood events the same methodology was used to calculate the modern flood peak discharges that yielded a deviation of only 3 6 between the reconstructed and measured peak discharges further verifying the acceptance of this method for the reconstruction of paleoflood peak discharges this studyexpanded the database of the palaeoflood hydrology research in the weihe river and the expanded database may be useful in providing important information for projects such as water conservancy hydropower engineering construction flood control and disaster mitigation

fluvial changes of the guadalquivir river during the holocene in cordoba southern spain this research was funded by a grant from proyectos de cordoba siglo xxi coordinated by prof r jose roldan canas universidad de cordoba

palaeoflood and floodplain records from spain evidence for long term climate variability and environmental changes abstract palaeoflood chronologies from seven spanish river basins and floodplain aggradation chronologies from thirteen rivers are analysed these fluvial records were divided in to two sub sets namely atlantic 10 ka record and mediterranean 3 ka record river basins which represent distinct modern hydroclimatic conditions in atlantic basins floods result from intense widespread rainfalls associated with atlantic frontal systems transported by westerly airflow mediterranean river flooding is related to heavy rainfall induced by mesoscale convective systems mcss during autumn months evidence from radiocarbon dates in slackwater flood deposits shows six periods of flood clusters at 10 750 10 240 9550 9130 4820 4440 2865 2350 960 790 and 520 290 cal bp despite the different flood producing weather conditions in atlantic and mediterranean rivers the radiocarbon sample clusters overlap and indicate changes in large scale atmospheric circulation and climatic conditions in the iberian peninsula comparison with proxy records of mean temperature for the northern hemisphere demonstrates a relationship between the period of slackwater flood deposition and cold climatic phases e g the 2650 yr bp climatic event or ad 1590 1650 period of the little ice age radiocarbon dates from aggraded floodplain sediments were clustered at 2710 2320 2000 1830 and 910 500 cal bp the first cluster period is in phase with the timing of slackwater deposition whereas the third 910 500 cal bp occurs in between two periods of increased flood frequency as indicated by the palaeoflood and documentary flood records it is argued that the 910 500 cal bp floodplain aggradation period reflects the first post roman evidence of environmental change related to generalised land use changes at the catchment scale which produced high sediment load transported to overbank areas during high flows

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

the holocene and upper pleistocene pollen record from padul granada spain a new study two borings were made at the site of padul granada pollen analysis of 200 spectra from two successive sequences 14 8 and 8 m deep enables a description of the vegetational and climatic history of this region the most southern one in europe from early wurmian times the chronology is supported by twenty one 14c dates original equivalents are found for the great european prewurm interstadials a markedly arid though thermically not extreme episode exactly equivalent to stage 4 of the marine isotopic stratigraphy closes this relatively temperate period the middle part of the last glacial shows climatic fluctuations that are poorly characterized as is often the case in europe for this period a long section very probably corresponding to the complete last pleniglacial does not show any climatic amelioration towards 15 000 yr b p a change in the diagram is noted that can only be interpreted as reflecting a larger expansion of a regional steppe cover this event also reported on three occasions in southeast france marks the beginning of the oldest dryas the climatic amelioration of ca 13 000 yr b p is far more pronounced here than anywhere else in europe whereas that at 10 000 yr b p is not so clearly marked this unexpected result may be accounted for by the fact that padul is the first continental site so far south and so near pleniglacial refuges to be known on the other hand this result is consistent with what is known from oceanic isotopic stratigraphy a quite new late glacial and holocene vegetational history is revealed characterized by the early appearance and dominance of quercus ilex oak forests of a southern type and the early occurrence of quercus suber and olea it is the first account of a complete history of the postglacial reafforestation in a region with a modern semi arid mediterranean climate from the palaeoclimatic point of view it shows that the hot and humid holocene optimum was attained slightly before 8000 yr b p and that the holocene climatic fluctuations were of but small amplitude

stratigraphic architecture and alluvial geoarchaeology of an ephemeral fluvial infilling climatic versus anthropogenic factors controlling the holocene fluvial evolution in southeastern spain drylands abstract two stages of depositional high discharge fluvial environments are recorded in the infilling of a rock shelter in a canyon of the segura river namely 1 first stage aggradational alluvial gravels in the lower part interpreted as braided channel bars seventh millennium to 2030 cal bc and 2 second stage slackwater flood deposits in the upper part between 2030 cal bc and after 900 ad during a stage of main channel incision reconstructed flood discharges for the second stage were a minimum of 700 m 3 s extreme palaeofloods that inundated the cave from the canyon inlet were successively higher and are correlated to quick rising flash floods the characteristics of cultural remains preserved by flood deposits reveal long periods of human cave occupation and passage through the canyon without extreme floods occurring these long periods of low discharge fluvial flow punctuated by catastrophic flash floods are linked to a torrential fluvial regime the torrential regime is the current hydrologic and climatic scenario in the streams of semi arid southeastern spain it is discusses the climatic versus anthropogenic factors affecting the fluvial development we conclude that the archaeo fluvial record of the pozo rock shelter indicates that the present day semi arid conditions of the southeastern spain drylands extend back to circa 4000 yr bp methodologically the combination of fluvial palaeohydrology and geoarchaeology appears to be a robust tool to reconstruct long term holocene climate changes

an early holocene short climatic event in the northwest iberian peninsula inferred from pollen and diatoms abstract pollen and diatom analyses have been carried out in a 490 cm long core collected from laguna lucenza 1420 m a s l northwest iberian peninsula spanning the last 10 000 yr pollen analyses show a decrease in deciduous quercus pollen percentages and total pollen concentration after radiocarbon date 8350 80 yr bp the estimated age by linear interpolation for the peak of this event is about 9200 cal yr bp diatom analyses have been carried out using the same samples in order to obtain complementary information about past environmental conditions within the water body pollen and diatom records show a response to changes in the palaeoenvironmental conditions diatom concentrations are relatively low indicating low productivity within the lake fragilaria species are dominant and fragilaria exigua is notably more abundant than during previous periods these changes in the diatom community reflect a decrease in lake ph this would be consistent with longer periods of ice cover and cold conditions in the lake at this time we interpret this episode as a response to climatic change probably due to climatic deterioration this interval coincides at least in part with an episode of abrupt and short widespread climate change lasting from 9000 to 8000 yr bp

changes in settlement patterns on the river rena southeast norway a response to holocene climate change the melting of the scandinavian ice sheet in the early holocene allowed humans to populate the northernmost parts of europe recent excavations of archaeological sites on the riverbank floodplain and kame terraces of the river rena southeast norway have defined periods of human occupation in riverside environments which became ice free during the last deglaciation in this paper we extend the scope of previous archaeological work by examining the sedimentology and chronology of five riverside sedimentary sequences along the river rena our aims were to reconstruct the holocene evolution of part of the river and determine whether changes in holocene settlement patterns might be linked to changes in river evolution and or climate results show 1 widespread draining of the kame terraces of the river rena occurred shortly before the first consistent human settlement in the area began c 8 ka bp 2 human settlement was maintained until the present day except during a period of previously undocumente

paleoenvironmental and geoarchaeological reconstruction from late holocene slope records lower huerva valley ebro basin ne spain abstract slope deposits in semiarid regions are known to be very sensitive environments especially those that occurred during the minor fluctuations of the late holocene in this paper we analyse holocene colluvium genesis composition and paleoenvironmental meaning through the study of slope deposits in ne spain two cumulative slope stages are described during this period in the study area both slope accumulations are superimposed and this has enabled an excellent preservation of the aggregative sequence and the paleosols corresponding to stabilisation stages 14c and tl dating as well as archaeological remains provide considerable chronological precision for this sequence the origin of the accumulation of the lower unit is placed around 4295 4083 cal yr bp 2346 2134 cal yr bc late chalcolithic and it developed until the iron age in a cooler and wetter climate cold iron age under favourable conditions a soil a horizon was formed on top of this unit a new slope accumulation was formed during the little ice age within the slope two morphogenetic periods ending with a horizons are distinguished and related with two main cold wet climatic events the study of these slopes provides a great amount of data for the paleoenvironmental and geoarchaeological reconstruction of the late holocene in ne spain

fluvial activity in major river basins of the eastern united states during the holocene in the eastern united states existing paleo reconstructions in fluvial environments consist primarily of site specific investigations of climate and human impacts on riverine processes this paper

the holocene fluvial chronology of spain evidence from a newly compiled radiocarbon database abstract a critical analysis of 74 radiocarbon dates selected from a total of 102 published and unpublished dates from holocene fluvial environments in spain has identified a number of periods of increased fluvial activity in spain namely 11 170 10 230 9630 8785 7980 6860 5800 4800 3880 3085 2895 1820 1300 0 cal bp the latter period reflecting sustained fluvial response to increased human impact the radiocarbon samples were classified according to type of depositional environment a alluvial overbank b flood basin c alluvial channel gravels d fluvio torrential deposits and e slackwater flood deposits palaeofloods dates from slackwater flood deposits indicated at least five phases of increased frequency of large magnitude floods during the holocene 10 855 10 230 9530 8780 2880 2430 975 790 and 520 265 cal yr bp flood basin type deposition occurred from 7980 to 4830 cal yr bp the main clusters of dates from alluvial floodplain deposits occurred at 2750 2150 and 930 520 cal yr bp the record is discussed in relation to other palaeoenvironmental archives including pollen records of holocene vegetation change and palaeoclimatic proxies such as the north atlantic drift ice record comparison with the latter indicates that major holocene flooding coincided with cold climate phases during 9530 9280 2880 2430 and 520 265 cal yr bp a cooling phase at 10 855 10 230 and warming phases at 9030 8780 and 975 790 cal yr bp

late holocene fluvial chronology of spain the role of climatic variability and human impact abstract a database of published and unpublished radiocarbon dates from late holocene fluvial environments in spain was critically analysed in order to obtain a fluvial chronology for this period the principal types of depositional environment represented in the record were slackwater flood deposits 28 dates alluvial overbank facies 12 dates and alluvial channel facies 7 dates the sedimentary context of each date was classified in order to identify those samples that specifically dated change in the fluvial environment analysis of the different depositional environment data sets using summed probability plots identified phases of alluviation at 2800 2350 and 800 500 cal bp increased frequency of large magnitude floods occurred at 2850 2500 1000 800 and 520 250 cal bp the results indicate that in mediterranean regions slackwater flood deposits are valuable archives of climatic variability even during periods of increased human impact

assessing the depth resolution of tomographic models of upper mantle structure beneath iceland 1 earlier inversions of body wave delay time data recorded during the icemelt portable broadband experiment imaged a cylindrical plume like low velocity anomaly extending to at least 400 km depth beneath iceland but the depth extent of the anomaly resolvable by tomography has recently been called into question we have performed several additional resolution tests to evaluate the depth resolution of tomographic models of the icelandic upper mantle the distribution of paths of body waves recorded by icemelt can distinguish among three different types of models a a wide and shallow anomaly b a narrow and deep anomaly and c a narrow and shallow anomaly while tomographic models contain an element of nonuniqueness these tests illustrate that the depth resolution of passive seismic experiments spanning subaerial iceland is adequate for distinguishing among alternative geodynamic models

palaeoflood record of the tagus river central spain during the late pleistocene and holocene abstract palaeoflood hydrology of the tagus river central spain was reconstructed from slackwater deposits and palaeostage indicators in two canyon reaches located at el puente del arzobispo in the central part of the catchment 35 000 km 2 in drainage area and in alcantara at the lower part of the catchment 52 000 km 2 in drainage area near the portuguese border the palaeoflood record with more than 80 flood events shows clusters of floods at specific periods from 9440 to 9210 14 c yr bp 8540 8110 bc 8500 to 8000 14 c yr bp 7500 7000 bc 6750 14 c yr bp 5000 bc 1200 to 950 14 c yr bp ad 785 1205 410 14 c yr bp ad 1450 1500 170 to 80 14 c yr bp ad 1670 1950 the largest flood s occurred during the periods 9440 to 9210 14 c yr bp 6750 14 c yr bp and 1200 to 950 14 c yr bp reaching minimum discharge estimates of between 4000 and 4100 m 3 s 1 in the el puente del arzobispo reach and 13 700 15 000 m 3 s 1 in the alcantara reach these periods with increased flood magnitude and or frequency in the tagus river are strongly related to increased moisture influx and winter precipitation in the iberian peninsula especially in the western zone proxy records sensitive to winter precipitation such as lake levels and vegetation changes indicated by pollen records are in good agreement with the clusters of floods found in the tagus river this flood variability seems to correspond to changes in the prevailing atmospheric circulation pattern affecting the iberian peninsula

late holocene flooding records from the floodplain deposits of the yugu river south korea abstract predicting responses of regional hydrological cycles to global warming requires an understanding of past hydrological events on various timescales this study investigated the variability of flooding as recorded in fluvial floodplain deposits the percentage of sand sized material in two cores collected from the floodplain of the yugu river one of the tributaries of the keum river central south korea has been tested as a proxy for the occurrence and magnitude of past flooding the sand fraction of the floodplain deposits in cores kl28 and kl29 which record deposition over the last 3500 years varied on multicentury timescales and suggests several past episodes of higher frequency large floods these clusters of large floods seem to correlate well with northern hemisphere temperature anomalies and suggest that more frequent large floods occurred during the medieval warm period mwp than during the little ice age lia the occurrence of more frequent large floods on the keum river tributary may have been driven by intensified northerly winds over east asia and resultant moisture convergence over korea and or a weakened thermal gradient between the tropical ocean and asian continent furthermore the centennial scale changes in the sand fraction of the floodplain deposits were partly similar to remote el nino southern oscillation enso activity implying a possible link between flooding in central south korea and enso activity this study has demonstrated that floodplain deposits have much potential for recording paleofloods though floodplains can be and quite often are very complex places in terms of their depositional history in regions where natural lakes suitable for the study of paleohydrology and paleoclimate are lacking well controlled time series data for the sand content at multiple sites in fluvial floodplains may be used to understand paleoflooding and extreme precipitation variability in the past

holocene floodplain sediment storage and hillslope erosion within the rhine catchment the response of fluvial systems to land use and climate change varies depending on catchment size while forcing response mechanisms of small catchments are reasonably well understood the response of larger drainage basins is less clear in particular the impact of land use and climate change on the rhine system is poorly understood because of the catchment size 185 000 km 2 and the long history of human cultivation which started approximately 7500 years ago a sediment budget is calculated to specify the amount of alluvial sediment that was deposited during the holocene and to estimate long term soil erosion rates the results suggest that 599 14 10 9 t of holocene alluvial sediment is stored in the non alpine part of the rhine catchment south and central germany eastern france the netherlands about 50 of holocene alluvial sediment is deposited along the trunk valley and the delta upper rhine lower rhine coastal plain while the rest is stored along the tributary valleys the floodplain sediment storage corresponds to a mean erosion rate of 0 559 0 16 t ha per yr 38 59 10 7 mm kyr across the rhine catchment outside the alps this holocene averaged estimate amounts for sediments that were delivered to the channel network and is at the lower limit of erosion rates from other studies of different methodology

the development and application of a database of radiocarbon dated holocene fluvial deposits in great britain abstract this paper reports on the development of a british database of 14c dated holocene fluvial units over the last 15 years since its inception in 1989 the database has undergone substantial expansion refinement and improvement together with considerable methodological development so that today it serves as a powerful research tool for investigating the spatial and temporal dynamics of holocene river development and flooding in great britain the improved analytical method is here applied to the currently existing database by examining datasets of 14c dated fluvial units from river basins that lie within and beyond the limits of late devensian glaciation this analysis indicates how the contrasted conditions in these two types of river environment have to an extent led to divergent records of flooding in response to holocene climate and land use change however even in the contrasting sedimentary records of upland glaciated and lowland unglaciated river basins six corresponding episodes of increased flood frequency are identified at c 5730 c 3540 c 2730 c 2280 c 660 and c 570 cal bp these represent widespread common responses from british river systems to large scale changes in climate the method of database construction and analysis outlined and demonstrated in this paper could be readily adopted in other parts of the world to improve our understanding of holocene river behaviour at the continental and global scale

the north atlantic subtropical anticyclone the semipermanent subtropical anticyclone over the north atlantic basin the azores high has a major influence on the weather and climate of much of north america western europe and northwestern africa the authors develop a climatology of the azores high by examining its spatial and temporal changes since 1899 using gridded surface pressure values anticyclones are identified when the daily pressure is 1020 mb and frequencies are tabulated for each half month from 1899 to 1990 principal components analysis is applied to analyze the anticyclone s spatial variance structure the azores high is dominated by two spatial modes a summer pattern in which high pressure dominates the atlantic basin and a winter pattern in which anticyclones are present over eastern north america and northwestern africa century long declines in these two modes indicate that there has been a net removal of atmospheric mass over the subtropical atlantic other modes include a meridional versus zonal circulation pattern and omega blocks time series of the mean annual principal component scores indicate that meridional flow has been increasing over the atlantic and that blocking anticyclones have become more prevalent over west central europe and less common over the northeastern atlantic and the british isles

environmental evolution and mid late holocene climate events in the valencia lagoon mediterranean coast of spain integration of geomorphological stratigraphic malacological sedimentological and micropalaeontological techniques and 14c dating allows us to characterise the processes and evolution of the coastal barrier lagoon system of valencia spain from the middle holocene to the historical epoch as well as the responses to global climate events four stages are recognised phase 1 around 8240 80 cal yr bp a brackish lagoon of moderate energy and in restricted environment was formed with an energy peak that could correspond to the maximum holocene marine transgression dating 8240 80 cal yr bp carried out in peat corresponds to a cold cycle and low water levels in inland lakes of the western mediterranean phase 2 from 6450 cal yr bp to 3710 130 cal yr bp a lagoon remained in restricted environment and connected with the sea but with a notable energy decrease and recurrent saturation processes similar to those described in other mediterranean continental lakes this phase is contemporaneous

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

river braiding caused by rapid floodplain deformation insights from holocene dynamics of the jarama river in central spain abstract in this paper we will use an illustrative example to show the significance of rapid vertical movements inside floodplains as well as varying discharge values for the alteration of channel and sedimentation patterns during the holocene concerning such relationships well documented and well dated references from sedimentary records are rather rare the developments within the lower jarama valley have been significantly supported by an interaction of tectonic activity evaporite dissolution and halokinetics that initiated rapid vertical movements over short distances and caused the formation of knick points and gradient changes along the longitudinal floodplain profile furthermore the specific mediterranean climate caused highly variable discharges including extreme runoff peaks the juxtaposition of different floodplain gradients gave rise to spatial and temporal changes of discharge patterns and channel geometry which is reflected by varying sedimentation as well as erosion patterns we have been able to confirm that alluvial thickening due to intense dissolution and subsidence has been a characteristic and frequently recurring feature during the pleistocene moreover we want to emphasize that also during the holocene gradient adjustments exercised controlling influence on fluvial dynamics in particular with regard to channel response in fact we found consistency between low and moderate gradients and meandering single channel patterns associated with overbank deposition in distal floodplain positions only a section with stronger inclination revealed evidences for multiple channel discharge patterns in form of gravelly braided river deposits in comparison with recent discharge patterns and information from historical sources it appears that braided river deposition took place just within a short time frame between 5 and 3 ka cal bp this matches exactly a period of strong climatic aridity including highly variable precipitation and discharge patterns from that we conclude that in the first instance gradient changes promoted the change of channel and discharge patterns but however specific overlap of the parameters gradient and runoff is considered to have been necessary to generate braided discharge pattern a subsequent formation of braided patterns during the late holocene was presumably prevented by river entrenchment as well as a strong increase of sediment availability during the time of roman colonization on the basis of this study we can establish a number of general relationships between floodplain gradient runoff pattern and channel response during the holocene period that may help us to better understand fluvial behavior in various different areas

floodplain evolution in the east midlands united kingdom the lateglacial and flandrian alluvial record from the soar and nene valleys this paper describes and interprets the floodplain stratigraphy of two low energy rivers in the east midlands u k and goes on to present an appropriate model of floodplain evolution that may be applicable to other lowland rivers in temperate mid latitudes work has been undertaken at the reach level to try and characterize the entire system in general only laterally extensive exposures have been used and detailed stratigraphic and microstratigraphic recording has been used to facilitate process interpretations all the sites have been radiocarbon dated the dataset consists of three sites in the soar valley and five sites in the larger nene valley the most common sedimentary architecture is a basal gravel with occasional shallow channels covered by a mixed loam sand silt clay of variable thickness with landsurfaces and evidence of bioturbation this loam is frequently interrupted by palaeochannels and finally all these sediments are buried by a massive silt clay unit most of the palaeochannels were abandoned in the early flandrian or between ca 3500 years bp and 2000 years bp the superficial silty clay is diachronous largely because of the irregular topography of the floodplain onto which it was deposited dates from non palaeochannel sections range from ca 3500 bp to ca 2100 years bp the floodplain stratigraphy has been profoundly influenced by soil development and sub aerial processes especially tree throw which has produced distinctive sedimentary structures the loam unit is interpreted as a soil which developed in between both silting palaeochannels and active channels the landsurfaces are both earlier and contemporaneous with the later phase of channel abandonment there is some evidence ca 5000 4000 bp of a rise in floodplain watertables an evolutionary model is proposed which can account for the stratigraphic evidence reported here it is based upon the development of an anastomosing stable multiple channel system from an initial braided river topography and its eventual conversion to a predominantly single channel system due to floodplain and channel siltation the reduction of channels is compensated for by a change in channel types and capacities while the floodplain aggrades this is the stable bed aggrading banks sbab model which necessitates no changes in discharges it is suggested that the sub meandering or straight to sinuous nature of many lowland u k channels may be due to their evolution from an anastomosing pattern where the least meandering channels survived typically with a box s shape planform and at the edges of the floodplain the sites also show that the lateglacial fluvial history of the two catchments seems to have been very different with incision and subsequent aggradation occurring during the younger dryas in the nene but not in the soar given the proximity and similarity of the two catchments this suggests that relatively minor local factors may have been able to push some catchments across fluvial thresholds in contrast the flandrian history of the two rivers has been broadly similar although there is evidence of greater lateral instability and floodplain reworking in the soar which may be due to hydrogeological factors or a different landuse history this work strongly suggests that new process based interpretations of floodplain stratigraphy and new models of floodplain evolution may be required before alluvial history can be easily related to the changing lateglacial and flandrian climate of lowland u k

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

interpreting alluvial archives sedimentological factors in the british holocene fluvial record abstract a holocene alluvial archive of 506 dated units for great britain is analysed in terms of the sedimentation styles involved the database is classified by sedimentation unit channel sediments palaeochannel fills floodplain surface sediments floodbasins and colluvial deposits and alluvial ensemble fans and cones upland gullies and streams braided systems and active inactive meandering and anastomosing systems floodplain palaeochannel and floodbasin sediments dominate the record mostly from meandering anastomosing systems different sediment units show varied potential for recording environmental change some are relatively poorly dated with respect to the volumes of material involved whilst many dates float in periods of depositional activity which lasted for extended time periods much dated activity is autogenic and of relatively little value in interpreting external environmental influence ensembles and units are similar in age patterns in some respects commonly they exhibit sets of short term peaks in sedimentation activity but differ in others floodbasins and to an extent braided systems feature in the earlier holocene whilst dated fan deposition is more evident in the late holocene there is a general bias towards sediment units of late holocene age which probably reflects preservation factors previous british holocene alluviation models are reviewed it is suggested that the majority of earlier models reflect partial views imposed by limited regional coverage and available dating

soils in the holocene alluvial sediments of the rio fraja valley spain in situ or soil sediments abstract in the holocene alluvial deposits of the fraja valley cadiz province sw spain we have used geomorphological mineralogical sedimentological and paleomagnetic data with dating based on radiocarbon and pottery to distinguish episodes of erosion sedimentation and pedogenesis during the last 4000 years the data sets allow us to distinguish soils formed in situ from transported soil sediments three depositional episodes have been distinguished two of them resulting in accretion of river alluvium and the third in colluvium that covers the floodplain sequence between 3000 and 1000 bp there were three periods of soil formation resulting in humic horizons these in situ soils are separated by four humic soil sediments all are similar in mineralogical composition and organic matter content but the magnetic intensity changes abruptly from 10 ma m 1 in the transported soil layers changes in declination are related to the continuing sedimentation and a brief paleomagnetic excursion is recognised at approximately 2000 bp

glacier and lake level variations in west central europe over the last 3500 years on the basis of glacier and lake level records this paper attempts for the first time a comparison between high resolution palaeohydrological and palaeoglaciological data in west central europe over the past 3500 years a data set of tree ring width radiocarbon and archaeological data in addition to historical sources were used to reconstruct fluctuations of the great aletsch the gorner and the lower grindelwald glaciers in the swiss alps the three ice streams experienced nearly synchronous advances at c 1000 600 bc and ad 500 600 800 900 1100 1200 and 1300 1860 these glacier fluctuations show strong correspondence with lake level variations reconstructed in eastern france jura mountains and pre alps and on the swiss plateau this supports the hypothesis of climatically driven fluctuations historical data available for the period since ad 1550 reveal in detail various meteorological conditions behind the successive glacier advances however in agreement with the general trend shown by th

anthropogenic and climatic impact on holocene sediment dynamics in se spain a review the climatic and anthropogenic control on holocene sediment dynamics was not well constrained for the western mediterranean basin the paucity of high resolution palaeoenvironmental records long hampered a detailed understanding of the human impact on erosion rates this paper analyses holocene sediment dynamics in the context of regional climatic conditions land cover and human occupation based on an extended compilation of recently published high resolution paleoenvironmental proxy data from both terrestrial and marine environments the palaeoenvironmental reconstruction identified four main aridification episodes a at 5600 4700 a4 4100 3400 a3 2800 2500 a2 and 1900 1300 1200 a1 cal bp most of the severe aridification phases were climatically induced not human driven and well correlated with a large dataset of paleoenvironmental records from the western mediterranean basin and north atlantic ocean the phases of enhanced aridity are generally associated with enhanced sediment dynamics independent of the intensity and type of human occupation in contrast wet climatic conditions are found to be associated with both high and low sediment dynamics dependent on the human impact on the environment the mid late phoenician phoenician ii republican rome civilizations and the christian reconquest are all associated with high human impact on the environment and high erosion rates are reported for the vera basin and ne spain despite the improved hydrological conditions human occupation is not necessarily associated with geomorphic instability as shown by the post argaric omeya and nazarene periods that are characterized by low erosion rates and geomorphic stability

interpreting drivers of change in fluvial archives of the western mediterranean a critical view abstract fluvial archives in particular late glacial to holocene floodplain records may provide valuable information regarding past environmental conditions and stages of landscape evolution in view of the high significance of floodplain dynamics for the development of entire landscapes the number of studies that have been performed on floodplain sediments remains comparatively low especially regarding the western mediterranean region however one of the reasons could be seen in the high complexity and diversity of processes and factors that control and influence fluvial activity that often hampers a straightforward interpretation of floodplain dynamics therefore a basic demand on fluvial archive research is to address the complexity of the factors that control the characteristics of fluvial sequences in order to provide a robust basis for their interpretation as a starting point for discussion this paper aims to give an overview of fluvial dynamic patterns in the western mediterranean for the last 15 ka in order to examine their relevance for palaeoenvironmental reconstructions the basis for this is provided by previous investigations on four different river systems in spain and northern africa the results of which are herein synthesized in order to propose a regional late pleistocene and holocene fluvial history for the western mediterranean realm basic results are related to alluvial floodplain deposits and visible features within them such as alluvial soils incision marks and aggradation phenomena since fluvial systems are open systems we discuss our findings against the background of different influencing factors that could modify fluvial architecture and may restrict palaeoenvironmental reconstructions a more comprehensive interpretation focuses on signals that are common to each of the studied river systems in this respect we critically discuss the customary nature of cumulative probability functions for the identification of regional flooding episodes and point out the benefits of a stratigraphy supported approach for characterizing regional floodplain dynamics finally three alluvial soil formation periods were found in all settings a first phase after 15 ka ending with the younger dryas event a second one from 7 to 5 ka with a break between 6 5 and 5 5 ka and a third phase between 3 and 2 ka these soil formation periods were interrupted and framed by fluvial dynamic phases accompanied by channel aggradation floodplain deposition floodplain erosion and or river incision in particular after 5 ka around 1 6 and at 1 ka and during the little ice age lia floodplain aggradation affected river systems in iberia and northern africa as well a cautious assessment of these results and extensive comparisons with secondary archive information prompts us to relate the aggradation periods with climate forcing by means of a supra regional aridification that effected large areas of the western mediterranean in contrast the three mentioned soil formation periods can be linked with landscape stability most probably triggered by favorable climate conditions in the western mediterranean apart from these large scale patterns we discuss the reliability of information emerging from floodplain records against the background of individualistic river behavior and self organization regarding future work we want to emphasize the great potential of yet rarely applied system oriented approaches that also attach importance to sub catchment dynamics as a link between catchment slopes and the main river floodplain

past hydrological events reflected in holocene history of polish rivers abstract a database of 335 radiocarbon dates from holocene fluvial sediments in poland has been compiled each sample is characterized by 25 parameters all samples were grouped into one of 7 regions characterized by hydrological regime and one of 8 depositional environments statistical analysis was used to enhance the palaeoenvironmental data and 17 phases may be distinguished 10 of which have a distinct sharp peak abandoned paleochannels 149 dates clearly reflect the major wetter phases of the holocene an opposite picture is presented by overbank aggradation 86 dates connected mainly with expansion of agriculture preliminary correlations are made on peat bog records changes in vegetation lake water level rates calcareous tufa and speleothems growth landslides phases and debris flow phases these show many convergences explained by climatic fluctuations during the holocene

the fluvial record of climate change fluvial landforms and sediments can be used to reconstruct past hydrological conditions over different time scales once allowance has been made for tectonic base level and human complications field stratigraphic evidence is explored here at three time scales the later pleistocene the holocene and the historical and instrumental period new data from a range of field studies demonstrate that croll milankovitch forcing dansgaard oeschger and heinrich events enhanced monsoon circulation millennial to centennial scale climate variability within the holocene probably associated with solar forcing and deep ocean circulation and flood event variability in recent centuries can all be discerned in the fluvial record although very significant advances have been made in river system and climate change research in recent years the potential of fluvial palaeohydrology has yet to be fully realized to the detriment of climatology public health resource management and river engineering

investigating extreme flood response to holocene palaeoclimate in the chinese monsoonal zone a palaeoflood case study from the hanjiang river abstract palaeoflood events recorded by slackwater deposits swds were investigated extensively by sedimentological criteria of palaeohydrology along the upper hanjiang river valley modern flood swds were collected for comparison with palaeoflood swd in the same reaches three typical palaeoflood swds were observed within holocene loess soil blanket on the first river terrace land the grain size distributions of palaeoflood swds are similar to modern flood swds whereas they are different from eolian loess and soil palaeoflood swd lies in three major pedo stratigraphic boundaries ts l 0 l 0 s 0 and s 0 l t in the holocene loess soil profiles the chronology of three palaeoflood episodes was established by osl dating and pedo stratigraphic correlation with the well dated holocene loess soil profiles in the upper hanjiang river basin holocene palaeoflood events were dated to 9500 8500 3200 2800 and 1800 1700 a b p respectively palaeoflood discharges were estimated by the palaeoflood model i e slope area method and step backwater method the highest discharges are 51 680 53 950 m 3 s 1 at the 11 500 time scale in the xunyang reach of the upper hanjiang river valley holocene extraordinary hydroclimatic events in the hanjiang river often result from abnormal atmospheric circulations from southwest monsoons in the chinese monsoonal zone these results provide a regional expression of extreme flood response to holocene palaeoclimate to understand the effects of global climatic variations on the river system dynamics

interrelated continental sedimentary environments in the central iberian range spain facies characterization and main palaeoenvironmental changes during the holocene a complex holocene system in the central iberian range ne spain has been reconstructed on the basis of sediments recovered from cores and in situ observations small alluvial fans graded into a wide shallow lacustrine area anavieja lake that connected downstream with a carbonate fluvial system with associated vegetated zones the fluvial system was mainly characterized by the development of tufa barriers especially during the first part of the holocene that separated pools or small lakes oncolites detrital tufas calcarenites and marls were deposited in these pools adjacent vegetated areas were covered by macrophytes and were episodically reached by detrital tufa supplies indicating high flood stages high sedimentary rates existed in both the fluvial including the pools and vegetated areas suggesting that despite the common erosion of tufas a clear aggradating evolution existed by contrast very low sedimentary rates were registered in the anavieja lake all the environments but especially the vegetated areas registered the climate evolution during the holocene although the onset of the holocene was characterized by wide climate variability warm and humid conditions dominated during the first part and drier conditions during the second part a water level recovery seems to have been existed during the last millennium this is a good example of the potential of continental systems other than lakes to be useful for palaeoenvironmental and palaeoclimatic studies

paleoflood hydrology and extraordinary flood events paleoflood hydrology is the study of past or ancient flood events the most accurate technique involves the analysis of slackwater deposits and paleostage indicators swd psi slackwater deposits are sand and silt emplaced from suspension in exceptionally deep high velocity floods that characterize narrow deep canyons in resistant geologic materials these and other paleostage indicators are used to establish hydraulic grade lines for the generating flow events favorable sites for slackwater deposition include channel margin areas where stresses and velocities are reduced below critical values necessary to maintain fine grained bedload material sand and silt in suspension computerized procedures for hydraulic flow modeling are used to tie the elevations of the highest slackwater deposits to surveyed river cross sections the flood discharges calculated by this method can be calibrated through the study of modern floods on gaged rivers correlation of multiple swd psi sites along a river reach is used to identify the maximum paleostage achieved by a given flood advances in the dating of flood deposits permit estimates of flood frequency to be made extending over a data base of thousands of years the major geochronologic tool is radiocarbon dating of various kinds of organic matter intercalated with the slackwater deposits an important development is the use of the tandem accelerator mass spectrometer for direct measurement of 14c tiny blebs of charcoal seeds and other organics can be analyzed in order to date ancient flood deposits of hydrologic significance since swd psi studies yield very accurate determinations of paleoflood ages and magnitudes there is a pressing need for new statistical procedures that make optimum use of the information content in paleoflood records for flood frequency analysis nevertheless swd psi paleoflood hydrology has moved beyond the research phase its use should be encouraged in evaluating past experience of extraordinary floods at appropriate hazardous sites

dynamics and extent of the weichselian permafrost in western europe substage 5e to stage 1 abstract a paleoclimate sequence and a map of the successive extensions of the permafrost during the different stages of the weichselian is proposed on the basis of cryopedological and paleopedological data this work shows the existence of two periglacial cycles within the weichselian both are characterized by later permafrost in the oceanic provinces of europe compared with northern france and belgium explanations are given for the origin of the pomeranian and dryas stadials

fluvial connectivity and climate a comparison of channel pattern and process in two climatically contrasting fluvial sedimentary systems in south africa abstract the aim of this research was to investigate the dynamics of valley formation sediment delivery and channel pattern in two climatically contrasting fluvial sedimentary systems in south africa each system comprised a network of headwater valley fills and floodplains underlain by sedimentary karoo supergroup rocks that are intersected by resistant dolerite dykes and sills the seekoei river floodplain and gordonville valley fill site in the great karoo however experience less than half the annual precipitation of the nsonge river floodplain and hlatikhulu valley fill in the kwazulu natal drakensberg foothills furthermore rainfall is more variable in the karoo despite climatic differences headwater valley fills were geomorphically similar in contrast floodplains in the two regions were vastly different even when the same downstream control a resistant dolerite intrusion crossing the drainage line was considered upstream of a dolerite dyke the nsonge river is highly sinuous and located in a wide floodplain that has been carved by lateral planation of the underlying bedrock in comparison the seekoei river located upstream of a dolerite sill is discontinuous and characterized by floodouts and avulsing distributaries that undergo periods of bedrock incision followed by infilling it is likely that this disparity is caused by the inability of infrequent unsustained flows to develop meanders and thus adjust the channel planform to changes in discharge sediment load and valley slope flow variability thus exercises a strong control on channel pattern and causes floodouts in headwater settings and the semi arid karoo floodplain as a result sediment transport in the seekoei river is likely to be episodic and net retention of sediment in the semi arid floodplain is greater than in the sub humid nsonge river floodplain where sediment depth is limited

paleoenvironmental and paleoclimatic conditions in the tagus river estuary during the last 14 kyr estuaries constitute the frontier between terrestrial fluvial and marine environments representing areas of high biological productivity that are particularly sensitive to global regional and local environmental and climatic changes the tagus river is the longest river of the iberian peninsula and has a catchment area of 80 629 km 2 in order to understand the interactions between the tagus system land river and the ocean we have studied a 52 76 m long core collected at the upper tagus estuary off vila franca de xira vfx 38 56 24 n 8 56 19 w 2 meters elevation the age model for this core was based on 6 ams 14 c dates and covers the last 14 calendar cal kyr bp 1 kyr 1000 yr sea surface temperature sst marine estuarine productivity and river input has been reconstructed with a high resolution multi proxy study that includes diatoms phytoliths c37 alkenones higher plant c23 c33 n alkanes and c20 c30 n alkan 1 ols fe ti and ca content derived from xrf analysis organic carbon corg and caco3 content and grainsize analysis although discontinuous the sst record shows a decreasing trend from early to late holocene as in the tagus prodelta sst record of rodrigues et al 2009 the lower sst values indicate that the river waters are colder than the coastal ocean important terrigenous input revealed by higher content of terrestrial lipid biomarkers fe and ti content fresh water diatoms and phytoliths is recorded during the younger dryas holocene transition 11 5 10 5 cal kyr bp as sea level rise allows sediment accumulation inside the estuary diatom marine and brackish genera and c37 alkenones appear between ca 11 5 4 cal kyr bp supporting the existence of a marine to brackish water environment as suggested by the previously suggested by vis kasse vandenberghe 2008 and vis kasse 2009 during this time interval relative maxima in diatoms c37 alkenones and corg show a cyclic increase in local productivity that can be explained as being a response to coastal water inflow and or fluvial supply of nutrients sst minima are recorded at 11 3 11 1 10 5 10 7 8 6 6 5 8 5 4 5 and 1 4 0 8 cal ka bp the estimated age for these episodes coincide with the equivalent events recorded in the north atlantic bond et al 1997 and in the tagus prodelta rodrigues et al 2009 higher terrigenous input episodes are recorded at 10 5 8 3 7 7 6 7 6 4 5 9 5 4 and 4 9 cal ka bp and could be related to flood events and or periods of major fluvial activity when comparing the sst minima with the markers of enhanced river discharge recorded at this site five of these events are ii seminario iberico igbp mudanca global mudanca global na peninsula iberica uma visao integrada 4 e 5 novembro 2010 lisboa portugal synchronous 10 5 7 8 7 7 6 7 6 6 5 9 5 8 and 5 4 5 cal ka bp corresponding to cold wet periods and coinciding with the flood events and or increased fluvial activity detected in the tagus river and in the iberian peninsula vis et al 2010 benito et al 2003 benito et al 2008 although higher resolution and a more accurate age model are needed to improve the understanding of this estuarine record the hydro sedimentary dynamics particularly during the holocene transgression appears to be controlling the terrigenous input and the local productivity recorded at this site still this sedimentary record provides information on past climate changes occurred in the iberian peninsula and contributes to a better understanding of the interactions between the north atlantic and the mediterranean

holocene alluvial morphopedosedimentary record and environmental changes in the bardenas reales natural park ne spain abstract a holocene alluvial morphostratigraphy based on geomorphological mapping sedimentological analysis soil development and radiocarbon chronology is presented for the semiarid blanca basin in the bardenas reales natural park ne spain four morphopedosedimentary alluvial units mu1 mu2 mu3 and mu4 were differentiated which may correspond to two palaeogeographical stages the first one includes the morphopedosedimentary unit mu1 and is the most extensive in the area it is made up of a complex aggradation fill up sequence comprising a braided channel system a sand mud flat 9200 7900 cal bp and a playa lake environment related to a nearly closed depression an intensive fluvial entrenchment period is recognized leading the opening of the blanca basin before the second stage that includes the units mu2 mu3 and mu4 this set of units forms a sequence of cut and fill and nested fill terraces recording the alluvial activity in the blanca basin during the last 6 ka the mu2 unit 5900 3300 cal bp in age represents a period of high geomorphic instability with rapid alluvial sedimentation channel incision oscillating changes on the other hand the mu3 unit has an age of 1050 500 cal bp and appears as a thin extensive alluvial cover overlying previous units finally the mu4 unit comprises superposition of numerous flood depositional sequences centimetric in scale dated from 450 10 cal bp the established soil chronosequence supports the numerical chronology of the four units these accumulation periods mu1 mu2 mu3 mu4 are associated with dry phases and or high hydrological variability floods and droughts at a regional scale changes on the north atlantic atmospheric circulation mode over southern europe may provide the key to explain the nature of alluvial activity during holocene in bardenas reales

meta analysis of holocene fluvial sedimentary archives a methodological primer this paper describes developments in the analysis and interpretation of holocene fluvial chronologies over the past 25 years particular consideration is given to meta analysis approaches pioneered by macklin and lewin 2003 using radiocarbon dated fluvial deposits in britain which have transformed fluvial geochronologies and correlations with climate and land use records worldwide during the last decade methodological developments have addressed issues such as correction for the shape of the radiocarbon calibration curve in the probability analysis of dated fluvial units and for variable alluvial unit preservation the number of regional database analyses of fluvial sedimentary archives has also expanded significantly during the past decade with studies now available for africa the mediterranean region india ireland new zealand poland the rhine catchment and the uk methods for incorporating optically stimulated luminescence ages in the probability analysis have also been developed and are illustrated using the database of eastern mediterranean dated fluvial deposits there is considerable potential for meta analysis research to inform long term flood risk assessment to evaluate short term climate and land use change impacts on flooding and river behaviour and to test landscape evolution models

a long term flood discharge record derived from slackwater flood deposits of the llobregat river ne spain abstract slackwater palaeoflood deposits were identified along two bedrock gorge study reaches of the llobregat river at pont de vilomara and monistrol de montserrat the compiled palaeoflood record consists of two principal flood series a a relatively complete record of low to high magnitude flood events from the last ca 100 years and b evidence of the largest palaeoflood events that have occurred over the last ca 2700 years the longer term extreme palaeoflood record indicates that the discharge of the 1971 flood the largest on record was exceeded on at least eight occasions with two periods of high magnitude flooding identified a the late bronze age 2500 2700 years ago and b the little ice age ad 1500 1700 at pont de vilomara palaeodischarge estimates of 3700 4300 m 3 s compare to a discharge of 2300 m 3 s for the 1971 event downstream at monistrol an estimate of 4680 m 3 s for flood deposits dated as ad 1516 1642 and believed to be those of the ad 1617 flood compared to 2500 m 3 s for the 1971 flood

past hydrological events reflected in the holocene fluvial record of europe abstract a comprehensive database of radiocarbon dated fluvial units in great britain poland and spain has been compiled to investigate the relationship between environmental change flooding and holocene river dynamics following the methodology recently developed by macklin and lewin macklin m g lewin j 2003 river sediments great floods and centennial scale holocene climate change journal of quaternary science 18 101 105 radiocarbon dates in fluvial sequences that coincide with a modification in sedimentation rate or style have been highlighted allowing geomorphologically significant changes in holocene river activity to be identified data analysis has been undertaken at both national and sub national scales and on catchments of different size type and land use history multiple phases of higher flood frequency characterized by accelerated erosion and sediment deposition on floodplains are recognized and compared with a range of climate proxies the relative and varying roles of climate and land use on river dynamics are considered and the value of the database for reconstructing past hydrological events as well as for predicting river response to future environmental change is assessed

holocene floodplain metamorphosis in the midlands united kingdom abstract many lowland rivers in the united kingdom including the nene soar and severn have layered floodplains with a basal gravel of pleistocene or late glacial age and a structureless silty clay superficial unit burying the entire former floodplain this burial is illustrated by the existence of variable mixed and pedologically disturbed sediments and palaeo landsurfaces between the basal gravels and superficial silty clay this paper presents a comparison of the pre and post late holocene palaeo landsurfaces and palaeochannels using data from the nene soar and severn valleys from this comparison it is argued that during the mid to late holocene ca 4500 yr bp to 2500 yr bp floodplains and river channels underwent a metamorphosis this is indicated by accelerated vertical accretion a reduction in floodplain relative relief changed floodplain soil conditions a reduction in channel w d ratios and a resultant increase in the silty clay proportion of channel perimeter sediments there are indications that hydrological change preceded this metamorphosis but the primary cause was an increase in fine sediment supply during the later holocene and a disequilibrium between channel bed and floodplain aggradation rates resulting in relative incision this metamorphosis which is explained in this paper by the proposed stable bed aggrading banks model sbab is the key factor in the holocene evolution of low energy floodplain systems in the united kingdom upon which more subtle short term fluctuations are superimposed

landscape sensitivity to rapid environmental change a quaternary perspective with examples from tropical areas abstract a millennial scale of rapid change during the quaternary is recorded in grip and gisp2 ice core records and is also found in tropical oceans rapid warming episodes followed by gradual cooling associated with sub milankovich cycles implies an asymmetry in the behaviour of climate that is likely to be reflected in landscape responses slope failures floods colluvial alluvial sedimentation may reflect short term changes in the record but reorganisation of slope and fluvial systems involves significant time lags or delays often on a millennial scale and requiring changes to the vegetation cover while some records of sedimentation indicate major landscape instability during last 20 ky or in the early holocene others indicate pulses of activity throughout the last glacial cycle lgc these differences may reflect regional patterns of climate change but also illustrate the importance of landscape sensitivity to our understanding of the impacts of rapid environmental change methodological problems arise in attempting correlations between site specific records of sedimentation and integrated signals of hydrologic change found in deltaic and off shore fans

solar influences on holocene climatic changes illustrated by correlations between past lake level fluctuations and the atmospheric 14c record chronological correlations established at different time scales among the lake level fluctuations in the jura and french subalpine ranges glacier movements in the swiss and austrian alps and the atmospheric 14c record during the last 7 millennia show coincidences between lake level rises glacier advances and high 14c production and vice versa these correspondences suggest that the short term 14c variations may be an empirical indicator of holocene palaeoclimates and argue for possible origins of holocene climatic oscillations 1 the varying solar activity refers to secular climatic oscillations and to major climatic deteriorations showing a ca 2300 yr periodicity 2 a question is raised about a relationship between the earth s magnetic field and climate first the weak strength periods of the earth s dipole magnetic field between 3800 and ca 2500 b c coincide with higher climate variability and vice versa second the ca 2300 yr periods revealed by the 14c record and also by the major climatic deteriorations re corded in jurassian lakes ca 1500 a d ca 800 b c and ca 3500 b c coincide with the ca 2300 yr periods revealed by the earth s nondipole geomagnetic field the present warming induced by anthropogenic factors should be intensified during the next few centuries by natural factors of climate evolution

a 35 000 year vegetation and climate history from potato lake mogollon rim arizona abstract a new record from potato lake central arizona details vegetation and climate changes since the mid wisconsin for the southern colorado plateau recovery of a longer record discrimination of pine pollen to species groups and identification of macrofossil remains extend whiteside s 1965 original study during the mid wisconsin ca 35 000 21 000 yr b p a mixed forest of engelmann spruce picea engelmannii and other conifers grew at the site suggesting a minimum elevational vegetation depression of ca 460 m summer temperatures were as much as 5 c cooler than today during the late wisconsin ca 21 000 10 400 yr b p even cooler temperatures 7 c colder than today ca 800 m depression allowed engelmann spruce alone to predominate warming by ca 10 400 yr b p led to the establishment of the modern ponderosa pine pinus ponderosa forest thus the mid wisconsin was not warm enough to support ponderosa pine forests in regions where the species predominates today climatic estimates presented here are consistent with other lines of evidence suggesting a cool and or wet mid wisconsin and a cold and or wet late wisconsin climate for much of the southwest potato lake was almost completely dry during the mid holocene but lake levels increased to near modern conditions by ca 3000 yr b p

a high resolution study of holocene paleoclimatic and paleoceanographic changes in the nordic seas 1 high resolution records from images core md95 2011 in the eastern norwegian sea provide evidence for relatively large and small scale high latitude climate variability throughout the holocene during the early and mid holocene a situation possibly driven by consistent stronger westerlies increased the eastward influence of arctic intermediate and near surface waters for the late holocene a relaxation of the atmospheric forcing resulted in increased influence of atlantic water the main changes in holocene climate show no obvious connection to changing solar irradiance and spectral analysis reveals no consistent signature for any periodic behavior of holocene climate at millennial or centennial timescales there are however indications of consistent multidecadal variability

urban geo archaeology in medieval alzira prov valencia spain abstract alzira is situated in a cut off meander loop of the rio jucar geo archaeological study shows that the islamic city wall was built during the second quarter of the 11th century ad at a time when the river had a low amplitude and low energy flood regime after mid century overbank silts began to invade the city as peak flood discharge increased with a spate of destructive floods reflected by high energy deposits during the late 11th century urban expansion within the city wall is dated to the later 11th or early 12th century interrupted by local abandonment and moderate energy flood silts major construction during the mid 12th century was followed by protracted abandonment after a siege in ad 1171 and further moderate energy flood silts that redistributed occupation and collapse debris reoccupation during the late 14th century was terminated by catastrophic floods in 1517 and 1571 after which much of the western end of alzira was not rebuilt following further flood catastrophes during the 17th century parts of the central walled city remained abandoned until the 19th century with new occupation atop flood sands of yet another disaster in 1864 the change in flood regime after 1150 was a result of deforestation of the watershed but progradation of a downstream tributary fan after 1517 created an unstable aggrading floodplain increasingly prone to severe flooding climatic anomalies were responsible for periods of recurrent severe floods archaeologically verified during the 11th and 12th centuries and historically documented beginning in 1318 the geo archaeological methodology illuminates the constructional and settlement history of alzira allows distinction of fluvial and cultural components and provides the necessary microstratigraphic detail and dating control to document the true complexity of alluvial processes during the last 1000 years

response of extreme floods in the southwestern united states to climatic variations in the late holocene a regional synthesis of paleoflood chronologies on rivers in arizona and southern utah reveals that the largest floods over the last 5000 years cluster into distinct time periods that are related to regional and global climatic fluctuations the flood chronologies were constructed using fine grained slackwater deposits that accumulate in protected areas along the margins of bedrock canyons and selectively preserve evidence of the largest events high magnitude floods were frequent on rivers throughout the region from 5000 to 360014c yrs bp dendrocalibrated age 3800 2200 bc and increased again after 2200 bp 400 bc with particularly prominent peaks in magnitude and frequency around 1100 900 bp ad 900 1100 and after 500 yrs bp ad 1400 in contrast the periods 3600 2200 bp 2200 400 bc and 800 600 yrs bp 1200 1400 ad are marked by sharp decreases in the occurrence of large floods on these rivers in the modern record storms that generate large floods 10 year in the region fall into three categories 1 winter north pacific frontal storms 2 late summer and fall storms that draw in moisture from recurved pacific tropical cyclones and 3 summer storms mainly convective thunderstorms winter storms and tropical cyclones are associated with the most severe floods on the rivers in this study and are the most probable causes of the paleofloods over the last 5000 years floods from both winter storms and tropical cyclones occur when deep mid latitude troughs steer storm systems into the region composite anomaly maps of daily 700 mbar heights indicate that these floods are associated with a low pressure anomaly off the california coast and a high pressure anomaly over the aleutians or gulf of alaska a strong connection exists between the negative phase of the southern oscillation index often associated with el nin o conditions and the large floods associated with winter storms and tropical cyclones the paleoflood records confirm the existence of centennial scale variations in the conditions conducive to the occurrence of extreme floods and flood generating storms in this region the episodes with an increased frequency of high magnitude floods coincide with periods of cool wet climate in the western u s whereas warm intervals such as the medieval warm period are times of dramatic decreases in the number of large floods a positive relationship between the paleofloods and long term variations in the frequency of el nin o events is evident over the last 1000 years this relationship continues over at least the last 3000 years with warm coastal sea surface temperatures indicative of el nin o like conditions

the librilla rambla an example of morphogenetic crisis in the holocene murcia spain the librilla basin is situated in the southeast of spain it is a tributary of the guadalentin river which drains an active rift bounded by the alhama fault the longitudinal profile of the librilla rambla is uneven rock bars such as at fuente librilla have trapped the deposits conveyed by the librilla torrent ramblas and the guadalentin river geomorphic processes have remodelled the sediments into polygenetic debris fans in several stages between 6500 and 2500 bp the holocene fills contain archaeological artefacts charcoals pollen and remains of human settlements that allow reconstruction of a protohistoric morphogenic crisis in this area which is characterised today by a mediterranean semi arid climate

vertical accretion sand proxies of gaged floods along the upper little tennessee river blue ridge mountains usa abstract understanding environmental hazards presented by river flooding has been enhanced by paleoflood analysis which uses sedimentary records to document floods beyond historical records bottomland overbank deposits e g natural levees floodbasins meander scars low terraces have the potential as continuous paleoflood archives of flood frequency and magnitude but they have been under utilized because of uncertainty about their ability to derive flood magnitude estimates the purpose of this paper is to provide a case study that illuminates tremendous potential of bottomland overbank sediments as reliable proxies of both flood frequency and magnitude methods involve correlation of particle size measurements of the coarse tail of overbank deposits 0 25 mm sand from three separate sites with historical flood discharge records for the upper little tennessee river in the blue ridge mountains of the southeastern united states results show that essentially all floods larger than a 20 probability event can be detected by the coarse tail of particle size distributions especially if the temporal resolution of sampling is annual or sub annual coarser temporal resolution 1 0 to 2 5 year sample intervals provides an adequate record of large floods but is unable to discriminate individual floods separated by only one to three years measurements of 0 25 mm sand that are normalized against a smoothed trend line through the down column data produce highly significant correlations r 2 values of 0 50 to 0 60 with p values of 0 004 to

paleoflooding reconstruction from holocene levee deposits in the lower meuse valley the netherlands this study investigates the holocene levee deposits and paleoflooding history of the lower meuse in the netherlands based on archeological investigations and sedimentary analyses grain size end member modelling magnetic susceptibility and thermogravimetric analyses the levee on the left bank in the study area near ooijen contains a continuous sedimentary record in the nw downstream part the archeological evidence and sedimentary results including a grain size based flood energy index lfei indicate that the lower meuse experienced a quiescent flooding period and low sedimentation rates during the mid late mesolithic when the levee was low and human influence was minor deposition during the mesolithic shows a fining upward trend and a highly developed soil containing abundant artefacts during the neolithic and bronze age the flooding intensity was low but gradually increased to a moderate level probably because of deforestation and increased runoff limited bronze age findings may reflect decreased human activity because of the increased flooding starting from the iron age the meuse experienced a generally enhanced flooding regime which is reflected by erosion and coarsened sedimentation in the iron age and roman period the high peak discharges during the iron age may have re opened a low lying paleochannel near to the levee during the intensified floods this general increasing trend is interrupted by the lower flooding phase in the early middle ages dark ages from the middle to the late middle ages the floods intensified again the coarsening deposition and higher sedimentation rates since the iron age resulted from increased floods and higher sediment supply by deforestation and soil erosion the findings of this study agree with a recent paleoflood reconstruction for the lower meuse by using a floodplain archive implying that levee sediment records have potential in paleohydrological studies if the completeness of the record and chronological information is guaranteed 2019 elsevier b v

crossing forest thresholds inertia and collapse in a holocene sequence from south central spain a holocene palaeoecological sequence from villaverde south central spain is presented the pollen stratigraphy is used to infer past vegetation changes within a catchment area that represents the boundary between semi arid plateau and mountain vegetation from c 9700 7530 cal yr bp pinus is dominant probably as a result of a combination of a relatively dry climate and natural fire disturbance from c 7530 5900 cal yr bp moderate invasion by quercus appears to be a migrational response following increased moisture and temperature but in part shaped by competitive adjustments from c 5900 5000 cal yr bp the pine forests are replaced by deciduous quercus forests with an important contribution from corylus betula fraxinus and alnus mediterranean type forests spread from c 5000 to 1920 cal yr bp coincident with expansions of artemisia juniperus and other xerophytes from c 1920 1160 cal yr bp pinus becomes dominant after a disturbance mediated invasion of the oak forests human impact u

holocene flooding history of the lower tagus valley portugal the present paper aims to reconstruct the lower tagus valley flooding history for the last ca 6500 a to explore the suitability of pollen based local vegetation development in supporting the reconstruction of flooding history and to explain fluvial activity changes in terms of allogenic climate human impact and autogenic system intrinsic processes the flooding history has been determined by cored sedimentary records located 18 km apart in distal low energy backswamps on both sides of the tagus channel in these low energy backswamps fine grained sediment layers deposited from suspended load of overbank flood water reflect periods with multiple overbank floods by means of a multi proxy approach sedimentology magnetic susceptibility grain size loss on ignition carbonate content and pollen sedimentary and environmental changes were identified at both sites synchronous lithological intervals accumulated suggesting a common origin for the changes in fluvial activity since ca 6500 cal a bp based on lithological changes three phases of high fluvial activity 6500 5500 4900 3500 and 1000 0 cal a bp and two phases of low fluvial activity 5500 4900 and 3500 1000 cal a bp were identified two periods with dominant allogenic controls on fluvial activity in the lower tagus valley were identified relative sea level 6500 5500 cal a bp and human impact 1000 0 cal a bp during the intermediate period changes in fluvial activity may have been caused by climate 5500 1000 cal bp but unambiguous correlations are difficult to make this is due to the way allogenic controls are translated through the fluvial system the geomorphological differences between upstream and downstream studies and autogenic processes the comparison of local vegetation development and flooding phases as reconstructed using sedimentology shows a limited added value of using local palynology as a proxy for fluvial activity 2010 john wiley sons ltd

the little ice age in iberian mountains abstract the little ice age lia is known as one of the coldest stages of the holocene most records from the northern hemisphere show evidence of significantly colder conditions during the lia which in some cases had substantial socio economic consequences in this study we investigated the magnitude and timing of climate variability during the lia in the mountains of the iberian peninsula based on a wide range of natural records including from glacial periglacial and lacustrine peatland areas fluvial alluvial deposits speleothems and tree rings historical documents and early instrument data the onset of the lia commenced in approximately ce 1300 and cold conditions with alternating moisture regimes persisted until approximately ce 1850 the environmental responses ranged from rapid e g tree rings to delayed e g glaciers the colder climate of the lia was accompanied by severe droughts floods and cold heat waves that showed significant spatio temporal variation across the iberian mountains several phases within the lia have been detected including a 1300 1480 increasing cooling with moderate climate oscillations b 1480 1570 relatively warmer conditions c 1570 1620 gradual cooling d 1620 1715 coldest climate period of the lia particularly during the maunder minimum with temperatures approximately 2 c below those at present e 1715 1760 warmer temperatures and a low frequency of extreme events f 1760 1800 climate deterioration and more climate extremes i e cold and heat waves floods and droughts g 1800 1850 highly variable climate conditions alternating with stability 1800 1815 extreme events 1815 1835 and a slight trend of warming associated with intense hydrometeorological events 1835 1850 h since 1850 a gradual staggered increase in temperature of approximately 1 c post lia warming has led to substantial changes in geo ecological dynamics mainly through shrinking of the spatial domain affected by cold climate processes

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

coarse sediments in northern apennine peat bogs and lakes new data for the record of holocene alluvial phases in peninsular italy this research was conducted in the northern apennines in the upper valleys of the cedra river and parma river occupied by glaciers during the last glacial maximum the stratigraphy the dating and the interpretation of the environmental significance of alluvial deposits interbedded between lacustrine sediments are reported the data provide an overview of the periods of enhanced alluvial activity that occurred after the glacial retreat in the apennine chain the alluvial phases and the periods of environmental stability varied in frequency and length during the holocene in particular starting from the beginning of the apennine neoglacial about 4 2 kyr bp the events became much more frequent but shorter the elapsed time between alluvial phases i e the length of the phases of stability was greater during the early holocene probably because of the values of insolation when the insolation in july was lower the length of the phases of stability was greater despite the uncertainty in the dating o

cumulative probability functions and their role in evaluating the chronology of geomorphological events during the holocene cumulative probability functions cpfs for large numbers of radiocarbon age determinations are increasingly being used by scientists as a methodology to discern environmental histories while the recent compilation of regional databases of the radiocarbon dating control for fluvial sediment sequences has been beneficial for identifying gaps in knowledge and stimulating new research there are a number of problems that critically undermine the use of these cpfs as sensitive hydroclimatic proxies i the cpf method is underpinned by the assumption that each radiocarbon measurement is a true age estimate for a point in time whereas each measured age in fact forms a scatter around the true age of the sample ii calibration of radiocarbon ages is responsible for much of the structure in cpfs and compounds the problem of scatter and smears the chronological control iii the databases incorporate multiple types of environmental changes differing chronological relationships between the 14c measurements and the dated events with pre dating dating or post dating chronological control each displaying variable length temporal lags all mixed together in the same analysis and iv the radiocarbon ages from individual case studies need to be more robustly tested before being incorporated into regional databases all these factors negate the value of cpfs as sensitive proxies of environmental change because peaks in probability for individual radiocarbon measurements are likely to be an incorrect estimate for the age of a geomorphological event and this problem is compounded by combining probabilities for multiple unrelated events in this paper we present a critical analysis of cpfs and their interpretation before suggesting alternative approaches to analysing radiocarbon geochronologies of geomorphic events which include i bayesian age modelling of river terrace development ii developing regional databases that test specific geomorphic hypotheses iii bayesian age modelling of palaeoflood records and iv analysis of sedimentation rates copyright 2011 john wiley sons ltd