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The present study examines the geoarchaeological history of an oasis in Kharga Depression in central Egypt. El-Deir is renowned for its Ptolemaic temple and Roman fortress on the road from former Hibis (Kharga) to the Nile Valley. During the survey, spring mounds and irrigation soils belonging to an ancient agricultural zone were discovered, and further documented by ceramics found on the site. Our methodology combines the geomorphological interpretation of landforms (especially yardangs) with ceramics and 14C-dated charcoal to distinguish and date former agricultural areas in El-Deir. The results show that the oasis experienced several phases of soil accretion and destruction through time. Playa sediments were deposited in the humid early Holocene and severely eroded by deflation before the onset of irrigated agriculture between Pharaonic and Persian times. Very fast vertical soil accretion occurred in the Ptolemaic period, but irrigation soils were later destroyed during the Roman period by a combination of wind deflation and flash floods (second to fourth century A.D.), suggesting a period of climate instability. The case of El-Deir invites reevaluation of constructive agencies for the development of irrigated land and destructive agencies as limiting factors for the sustainability of agricultural practices in late antiquity. [ABSTRACT FROM AUTHOR]

Abstract: The Lower Mekong River has been an important research topic for at least 15years, notably in the fields of hydrology, fluvial geomorphology, and the impact of dams. Recent papers refer mostly to the impact of the Lancang chain of hydroelectric dams constructed on the Chinese section of the river. Among the pending scientific questions are (1) the upstream–downstream variations in the concentration and yield of suspended sediment and (2) the relative importance of sand in the total yield. The general consensus among the scientific community is that the relative importance of sand in suspended load is not the main scientific concern despite its extensive presence in the Mekong River channel, as noted by geomorphologists, and despite its extreme importance for the stability of the delta shoreline in Viet Nam. This paper contradicts the general consensus. Its objective is to present new information on the processes of sand transport in the Lower Mekong channel. Imagery, field observations, sampling on the river banks, and grain size analysis of sand deposits have been carried out between Chiang Sean (downstream of the Chinese border) and the delta. The C–M image technique served to discriminate between the various transport processes (bedload and different types of suspension). This technique helps in understanding the changing processes responsible for downstream sediment transfer in river channels. The results of this study are the following. [(1)] Discrepancies in the values of annual suspended-sediment load detected by different gauging stations have not yet been satisfactorily explained. The CM image technique indicates that grain size and the quantity of sand transiting in suspension vs. bedload vary from upstream to downstream. [(2)] These upstream–downstream differences may be related to the energy of floods. Energy helps to explain longitudinal variations in the relative importance of the different modes of transport and serves to distinguish between bedload, graded and uniform suspension, and wash load. [(3)] The Mekong is seen as a river carrying mostly silt and clay; however, the results suggest that sand plays a major role in downstream sediment transfer during floods. This result is in line with the large amounts of sand present in the channel. Its relative importance in the total yield must be reassessed, as suggested by Walling (2005, 2008). As may be expected, the role of sand in the stability of the delta shoreline is of prime importance. [Copyright &y& Elsevier]

Abstract: Recent geoarchaeological investigations have been carried out in the thick silty alluvial formations of the northern Hadramawt basin (Yemen). Field data was combined with a compilation of palaeoenvironmental records published from Arabia and its margins. Research performed on palaeolakes and other geoarchives indicates that the wet early-mid Holocene has little in common with the continuously arid period after 5.2 ka BP. The data sets allowed the authors to propose new perspectives for the Holocene palaeohydrological evolution of Southern Arabia, which was more variable and contrasting than previously thought. Furthermore, these data provide the opportunity to go deeper into the Holocene and to present a new precise palaeohydrological framework for the Late Holocene (7.0–2.0 ka BP). River functioning, fluvial aquifer dynamics and types of sedimentation are closely related to the rainfall regime, length and intensity (monsoonal or Mediterranean), and to the landscape conditions in the upper watersheds. The development of fluvial palaeosols in the Hadramawt valleys, often associated with high levels of the aquifers, is clearly in phase with humid periods until the beginning of the first millennium BC (5.9–5.3, 4.8–4.5 and 4.0–2.7 ka). River behaviour also impacted Neolithic and early Bronze Age settlement systems in this lowland area, as phases of floodplain stability favour site location. The hyperarid 4.2 ka event is associated with an unprecedented fluvial detrital phase with high energy discharges in the entire Hadramawt basin. [Copyright &y& Elsevier]

Abstract: This study presents the upstream–downstream complexity of the Rhone, which earlier was a braided river. The fluvial patterns of the Rhône ca. 1860–70 are discussed, i.e. at the end of the Little Ice Age, which was also the beginning of the period of river dredging for improving navigation in the channel (1840–1930) and before the development of a chain of hydroelectric dams (1892–1986) on the river. Flowing across Switzerland and France to the Camargue delta on the Mediterranean, the Rhône drains the western part of the Alps in Europe. Befitting a large river flowing from the mountains, the Rhône was braided along most of its course, due to large quantities of coarse sediments formerly contributed by tributaries from the Alps, Jura Mountains, and Massif Central. The paper begins with a summary of palaeo-environmental studies on the Rhône, which show that the river experienced several events of fluvial metamorphosis during the Holocene. The reaches, which were braided during the late 19th century, alternated between meandering and braided patterns during this period due to the high sensitivity of the channel pattern to external variables such as changing water and sediment discharges. A discussion on the methods used to describe different aspects of the braided pattern of the Rhône from 1860 to 1870, using large-scale maps follows. Discrete reaches on the river are identified using slope, downstream variations of discharge, and stream power. These can be attributed to three factors: the tributaries (large supplies of bed load are brought by the Arve, the Ain, the Drôme, the Ardèche and the Durance rivers), Quaternary tectonics, and the along-channel distance from tributary confluences. Finally, the study assesses the pre-modern conditions of the Rhône for restoring selected reaches on the modern river. [Copyright &y& Elsevier]

The Malnant River is a rapidly incising river with a French name that translates as “bad creek,” reflecting local opinion of the hazards from dramatic channel changes that have occurred in the last few centuries. Downcutting in the last three decades has created severe problems for farmers in this small watershed (16 km2) as bridges are undermined, streamside roads are threatened, and irrigation diversion structures are rendered unusable. The purpose of our study was to determine the extent and causes of downcutting. A detailed landcover map dated 1732 revealed that forest cover had been reduced by that time to 10% of the present-day cover. The Malnant was strongly affected by floods and debris torrents during the 18th and 19th centuries that delivered massive amounts of sediment. During the 20th century, reforestation reduced the sediment delivery from hillslopes. In addition, gravel extraction in the Malnant and in the Fier River (of which the Malnant is a tributary) has lowered the base level for the river. This initiated a knickpoint that moved upstream. Weirs placed in the Malnant in 1968 were used to measure rates of bed incision in the field. With a mean width of 4.0 m and degradation up to 36 cubic meters per meter channel length, the lower 4.5 km of the Malnant has experienced a net loss of approximately 163,000 m3 of bed material. Above the 4.5-km point on the Malnant, bedrock controls exist that have arrested the upstream-progressing degradation. [Copyright &y& Elsevier]

Le rapport de Surell de 1841 ne s'est pas traduit me´caniquement dans le premie`re loi dite RTM de 1860. A` travers l'exemple du de´partement de la Droˆme, on voit comment, sur le terrain, les acteurs locaux e´voluent par rapport a` la question du reboisement, sur fond de crues re´pe´titives. [Copyright 2002 Elsevier]

In arid and semi-arid areas, characterized by limited and often torrential rainfall, climatic factors play an essential role in explaining soil loss at the basin scale. Indeed, the largest share of solid materials export occurs during floods. The present study deals with the evaluation and quantification of sediment transport in the Wadi El Hammam basin, a large sub-basin of the Macta watershed characterized by strong rates of erosion. The sensitivity of rocks to erosion, the intensity of rainfall, and the human-induced alterations to the flow regime explain why the flux of suspended solids (SS) transported by the Wadi El Hammam may reach very high values. The sediment budget related to the of rainfall–runoff–sediment transport process shows good relationships, especially between the equivalent discharge (Q) and the quantity of sediment transported (C). Statistical models to reproduce SS flux are presented. After calibration and validation of models at the measured time scales, they are used to reconstruct time series of SS flux estimated from historical data of water discharge and rainfall., The relationship C–Q was modelled at the flood scale and adjusted by a power function Y = aXb; statistical analysis of the constant a and exponent b was used to explain the behaviour of these two parameters and lead to a better understanding of the practical and theoretical aspects of the processes at work in the watershed. [ABSTRACT FROM AUTHOR]

Abstract: Over a historical timescale, landscapes have been strongly affected by fluctuations in climate and by the impact of human societies. This study examines the historical evolution of mid-altitude fluvial systems in the Western Alps and Cévennes (SE Massif Central) in the context of marked climate and anthropogenic change at the end of the Little Ice Age (late 19th century). This work contributes to the reconstruction of river paleodynamics by investigating the nature and chronology of geomorphological changes in upper river basins. In order to produce a detailed reconstruction of hydromorphological changes, we combined two approaches: the study of historical archives and the use of bioindicators (the dating of terraces using dendrochronology and of silt benches using lichenometry in order to reconstruct the evolution of the river channels). The 19th century is a particularly propitious period for the study of surface dynamics because archives have preserved a wealth of qualitative and quantitative data concerning rivers (economic statistics, meteorological and hydrological observations, illustrative documents, descriptions by contemporary observers). It is also a period for which reliable dating methods are available for detrital deposits in rivers. The period provides new information on how the transition between the Little Ice Age and current climate conditions affected the evolution of drainage basins and stream channels by highlighting a succession of phases in the erosive process (e.g., the preparatory role of the drought of 1830–1838 in the erosion crisis of 1855–1870) and refining the chronology of events (very early onset of riverbed incision). The results highlight the effect of climate (small hydroclimatic fluctuations), amplified by strong anthropization, on the rhythm of landscape change and on the relative stabilization of the landscape at the end of the 19th century. In addition, the synchronization of phenomena on the two sides of the Rhone Valley shows that these changes took place on a regional scale. [Copyright &y& Elsevier]

Abstract: The geomorphologic impact of the Little Ice Age (LIA) was determined on two French Mediterranean rivers, the upper Ardèche and the upper Loire. In order to evaluate the impact of the LIA on the hydrology of these rivers, two historical flood chronicles were made from historical sources. The LIA can be divided in three phases of high activity (1530–1700; 1750–1810; 1840–1910). A geomorphologic study of the two rivers shows that incision is the principle process at work in the 20th century. In order to date the low terraces and bedforms present in both valleys, lichenometry was used. Rhizocarpon geographicum allowed the main features on the bottom of the valley to be dated using two growth curves made for the two studied areas. In the Ardèche, lichenometric dating showed a progressive evacuation of the inherited alluvial stock. The oldest lichens found on the foodplain and the outcrops indicate that incision began between the second half of the 17th century and the end of the 18th century, in the mid Little Ice Age. Incision stopped on the bedrock in the second half of the 19th century. In the Loire, the narrowness of the gorge did not allow sediment to be stored during the first half of the LIA. Very old lichens (>1000 yr of age) are present on the bedrock close to the bed. However at a number of locations, the valley slightly widens, allowing sediment that was transiting through the gorge to be stored. The geomorphologic features that characterise these basins clearly show a hydrosedimentary behaviour different before and after the beginning of the 20th century. [Copyright &y& Elsevier]

Abstract: We present the research needs required to implement the European Framework Directive for Water, involving a better understanding of the ecosystem dynamics, a better knowledge of groundwater bodies, strong efforts in ecotoxycology and a new approach in water economics. To cite this article: P.-A. Roche et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

At the end of the first century BC, Ephesus became the Roman capital of Asia Minor and the most important commercial, religious, and cultural center of the region. In order to evaluate the status of anthropogenic fluxes in the port of Ephesus, a 12 m long sediment core drilled in the Roman basin was investigated to shed light on the paleo-environmental evolution of the harbor using grain size distribution analysis, 14 C ages, major and trace element geochemistry, and Pb isotope compositions. With the help of complementary sedimentological data and Principal Component Analysis, five distinct units were identified which, together, reflect the different stages of water history in the harbor. Among the major disruptive events affecting the port were earthquakes and military events, both of which were particularly effective at destroying the water distribution system. Seasonal floods of the Cayster River (Küçük Menderes) were the major source of the silt that progressively infilled the harbor. Silting in was further enhanced by the westward migration of the river mouth. A single major disruptive event located at 550 cm core depth and heralding the development of anoxia in the harbor marks the end of the dynamic regime that otherwise controlled the harbor water throughout the Roman Empire period. This remarkable event may correspond to a major disruption of the aqueduct system or to a brutal avulsion of the Cayster River bed. It clearly represents a major disturbance in the history of life at Ephesus. It is poorly dated, but probably occurred during the reign of Augustus or shortly after. Lead isotope and trace metal evidence suggest that in the four bottom units pollution was subdued with respect to other Pb metal inputs, presumably those from aqueducts and natural karstic springs. Near the top of the core, which coincides with harbor abandonment and the more recent period, anthropogenic Pb contamination is clearly visible in both Pb abundances and isotopic compositions. [ABSTRACT FROM AUTHOR]

Abstract: To the northwest of the ancient city of Ostia, the analysis of cores revealed a stratigraphic sequence, which we interpret as the filling of a harbour basin. This basin, located at the west of the so-called “Palazzo Imperiale” presents seven characteristics: (1) The maximum depth is 6 m below the Roman sea level. This depth allowed any type of ship (even heavy tonnage) to access the harbour. (2) A chronostratigraphic gap at −6 m below Roman sea level suggests digging operations in the basin (or subsequent dredging) that have caused the loss of sedimentary archives. (3) The filling consists of dark clays typical of a quiet environment but open to marine and river influences. (4) The dates at the base of this sequence give a range between the 4th and the 2nd century BC. (5) In the harbour sequence, a facies change at −2.5 m under the Roman sea level involves a change in the processes of sedimentation and/or operation. (6) No later than the beginning of the 1st century AD, the thickness of the water column in the basin is less than 50 cm and seems to be caused by a massive siltation following a succession of floods of the Tiber. (7) This basin was thus already abandoned during the start-up of Portus. [Copyright &y& Elsevier]