Gully development in the Moldavian Plateau of Romania

Gully erosion has been recognized as an important environmental threat in the Moldavian Plateau of Eastern Romania. The main objective of this study was to define the process-based gully development by providing quantitative information from long-term field measurements in small catchments.Three main areas of monitoring gullies were explored: aerial photographs of flights in 1960 and 1970, classical leveling and repeated survey through a particular close stakes grid after 1980. The Caesium-137 technique has been used effectively in the areas of deposition of gully sediments to obtain reliable information on dating specific levels of sediments and to provide chronological measures of gully development.Most of the discontinuous gullies exhibit both proper gullying, mainly if not exclusively by gully head advance, and aggradation of the gully basin floor. Results indicated that the mean gully head retreat was 0.92 m year^− 1 and the mean areal gully growth was 17.0 m² year^− 1. Both values indicate a slow erosion rate for this area. The average annual regime of gullying is pulsatory, one that is best described by great fluctuations. Conventional measurements on sedimentation over the period 1987–1997 indicate a higher rate of aggradation in the upper half of the gully floor. Information on the Caesium-137 depth profile was used to provide estimates of a mean sedimentation rate of 4.4 cm year^− 1 over the period 1963–1996 and 2.5 cm year^− 1 after 1986 for the short successive discontinuous gullies. A new classification of the discontinuous gullies based on two criteria, respectively, the field patterns and the rate of aggradation within the gully basin floor was established.For continuous gullies, linear gully head retreat, areal gully growth and eroded material rates were quantified for three periods (1961–1970, 1971–1980 and 1981–1990). Results indicate that gully erosion has decreased since 1960. This gullying decline is due to the rainfall distribution, and the increased influence of soil conservation practices. The mean gully head retreat of 12.5 m year^− 1 between 1961–1990 was accompanied by a mean areal gully growth of 366.8 m² year^− 1 and a mean erosion rate of 4168 t year^− 1. As with discontinuous gullies, continuous gullies showed pulsatory development.The critical period for gullying over 1981–1996 covers 4 months from Mid March to Mid July in an area with mean annual precipitation around 500 mm. Another main finding of this 16-year stationary monitoring was that 57% of the total gullying occurred during the cold season, with the remainder during the warm season. Of the total gully growth, 66% results from only four years (1981, 1988, 1991 and 1996), when a greater amount of precipitation fell.     

Redistribution of organic pollutants in river sediments and alluvial soils related to major floods

Background, Aims, and Scope  More frequent occurrence of stronger floods in Europe as well as in other parts of the world in recent years raises major concern about the material damages, but also an important issue of contamination of the affected areas through flooding. The effects of major floods on levels and distribution of contamination with hydrophobic organic pollutants were examined from the continuous set of data for floodplain soils and sediments from a model industrial area in the Czech Republic where a 100-year flood occurred in 1997. The goal of this study was to evaluate the risk related to contamination associated with such extensive natural events and characterize the spatial and temporal distribution and dynamics of pollutants related to a major flooding shortly after the floods and also in the time period several years after floods. Methods  Sediments and alluvial soils from fourteen sites each were repeatedly sampled during the period from 1996 until 2005. The sampling sites represented five regions. Collected top-layer sediment and soil samples were characterized and analyzed for hydrophobic organic pollutants PCBs, OCPs and HCB using GC-ECD and PAHs using a GC-MS instrument. Spatial and temporal differences as well as the relative distribution of the pollutants were examined in detail by statistical analysis including multivariate methods with special emphases placed on the changes related to floods. Results  The organic pollutants levels in both alluvial soils and sediments exceeded the safe environmental limits at numerous sites. Pollutants concentrations and relative distribution as well as organic carbon content in both sediment and floodplain soils were significantly affected by the flooding, which resulted in a decrease of all studied contaminants in sediments and significant rise of the PAH pollution in the flooded soils. There was a unique and highly conserved PAH pattern in soils regardless of the floods and greater changes in PAH pattern in sediments related to floods. The relative distribution of individual PAHs reflected a combustion generated PAH profile. PAH levels in the river sediments rose again at the sites with continuous sources several years after floods. Discussion  The results showed different dynamics of PAHs and PCBs during the floods when PAHs were redistributed from the sediments to alluvial soils while PCBs have been washed out of the study regions. The data reveal longer contamination memory and consistent contamination pattern in soils, whereas sediments showed more dynamic changes responding strongly to the actual situation. The stable PAH pattern within the regions also indicates that a relative amount of all compounds is comparable across the samples and, thus, that the sources at different sites have similar character. Conclusions  Sediments have the potential to function as a secondary source of contamination for the aquatic ecosystem, but also for the floodplain soils and other flooded areas. The floods served as a vector of PAHs contamination from sediments to soils. The reloading of river sediments in time, namely with PAHs, due to present sources increases their risk as a potential source in the next bigger flood event both to the downstream river basin and affected alluvial soils. Recommendations and Perspectives  The results stress the importance of including the floodplain soil contamination in the risk assessment focused on flood effects. Floodplain soils have stable long-term environmental memory related to contamination levels, pattern and distribution, whereby they can provide relevant information on the overall contamination of the area. The sediments will continue to serve as a potential source of contaminants and alluvial soils as the catchment media reflecting the major flood events, especially until effective measures are taken to limit contamination sources. ESS-Submission Editor: Dr. Henner Hollert (Hollert@uni-heidelberg.de) This article is openly accessible!     

Predicting vertical accretion rates at an archaeological site on the Mississippi River floodplain: Effigy Mounds National Monument,Iowa

The Sny Magill Unit of Effigy Mounds National Monument, Iowa, contains the largest cluster of prehistoric effigy mounds on public land in North America. The mounds are situated atop a low terrace of the Upper Mississippi River, where they are slowly being buried by overbank deposition during floods. The terrace surface includes forest soils with argillic (Bt) or cambic (Bw) horizons developed in up to 1 m of loamy overbank deposits on top of Pleistocene sand and gravel. Radiocarbon evidence suggests that overbank deposits have accumulated since the end of the mound-building period (about 700 years BP), yielding a vertical accretion rate of about 0.6 mm yr^− 1. On the basis of ¹³⁷Cs analysis, accretion rates over the past 40–50 years average 1.25–2.07 mm yr^− 1, with some evidence for a decreasing rate since 1964. If these accretion rates are projected forward, several of the effigy mounds could be buried by flood deposits within 150–300 years. This ¹³⁷Cs-derived estimate agrees closely with an estimate of burial times based on flood frequency and observed flood deposit thickness during recent floods. However, the floodplain and backwater environments of the Upper Mississippi River are aggrading much more rapidly than the Sny Magill terrace surface, suggesting that burial of the entire terrace could occur within 80–400 years and the entire mound group could be buried within 150–850 years. The projected accretion rates and time to burial are subject to large uncertainties because of environmental change in the watershed, including recent trends toward increasing flood stages and decreasing suspended sediment loads.     

Late Holocene land use at Orstad, Jæren, southwestern Norway, evidence from pollen analysis and soil micromorphology

Pollen analysis was combined with radiocarbon dating, physical, chemical and biological soil analyses and soil micromorphology, to investigate the prehistoric land use at Orstad, in Jæren, southwestern Norway.Orstad is an Early Bronze Age clearance cairn field in a cultural landscape with traces of land use back to the Neolithic. Samples were mainly collected from an 84 m long excavated trench with mainly podzolic soils. Although pollen preservation was poor, it was possible to differentiate five phases in the local vegetation and land use history. Human impact on the site could be traces back to about 4400–4000 BP uncal./3045–2600 cal. BC. Wheat and barley have been cultivated at Orstad during a period from ca. 3600 BP uncal./1945–1750 cal. BC until the Older Iron Age, when heather vegetation began to spread on the site.Soil micromorphology revealed different soil management practices for this time period: The soils seem to have been cleared by fire, prior to cultivation until ca. 3200 BP uncal./1610–1455 cal. BC. Then, new cultivation fields were laid out on higher levels, and seem to have been improved by adding of organic materials, mainly turves taken from podzolic top soils and peats from nearby localities.     

Relationships among rainfall, runoff, and suspended sediment in a small catchment with badlands

The Araguás Catchment of the Central Spanish Pyrenees has been monitored since 2004 to study weathering, erosion, and the hydrological and sediment response to rainfall events in order to understand the hydromorphological dynamics of a badland area in a relatively humid environment. This small catchment (0.45 km²) shows highly active processes of physical and chemical weathering related to seasonal variations in temperature and moisture. Erosion and sediment transport are widely studied in badlands within Mediterranean environments because they represent the dominant sediment source. To obtain information about suspended sediment and discharge, a gauging station was installed within the Araguás Catchment during the summer of 2005. The aim of this work is to determine the relationships among rainfall, runoff, and suspended sediment in this badland area. Towards this goal, we analyze the relationships between suspended sediment concentration and discharge during rainfall events.From a hydrological viewpoint, the Araguás Catchment reacts to all rainfall events with torrential flow being the most characteristic hydrological response. The results obtained between October 2005 and April 2007 reveal extremely high concentrations of suspended sediment, with values frequently exceeding 100 g l^{<modINS>−<!--[/INS]"> 1} and reaching a maximum of 1200 g l^{<modINS>−<!--[/INS]"> 1}. Three different types of hysteretic loops were observed: clockwise (22 events, 28%), counter-clockwise (27 events, 34%), and figure-eight (12 events, 15%). Moreover, 23% of events were classified as complex hysteretic loops and removed from the analysis due to their complexity. Clockwise hysteretic floods are characterized by their long duration and the highest hydrological and sedimentological responses; counter-clockwise hysteretic floods are characterized by their short duration and moderate hydrological and sediment responses; finally, figure-eight hysteretic floods are related to multiple peaks in suspended sediment, coinciding with oscillations in discharge associated with the highest rainfall intensities within each event and moderate hydrological and sediment responses.     

Holocene evolution of floodplain soils and landscapes in the Kulikovo field area

The lithostratigraphic, radiocarbon, macro- and micromorphological, particle-size, and other analyses have been applied to reconstruct the Holocene evolution of soils and landscapes on the high- and mediumlevel floodplains of the Nepryadva River in the Kulikovo field area. It is shown that the soils buried within the thickness of alluvial sediments on the high- and medium-level floodplains were formed in different times and had their own evolution patterns; the polygenetic nature of these soils is demonstrated. The development of floodplain landscapes in the Holocene was affected by the long-term climatic fluctuations. The bed of the high floodplain was formed during the Late Valdai glacial stage. The beginning of the development of an intricate sequence of buried soils and sediments of the floodplain dates back to the Boreal period. This pedosedimentary sequence in the studied area can be referred to as the Kulikovo sequence. In the course of its formation, the pedogenic stages with a predominant development of soils alternated with the lithogenic stages of active alluviation and deposition of colluvial deposits from adjacent slopes on the floodplain.     

Irrigation agriculture and the sedimentary record in the Palpa Valley,southern Peru

Irrigation agriculture is an ancient and widespread feature in regions where allogenic rivers flow through arid landscapes. This paper reports the results of sedimentological–pedological investigations in the Palpa Valley in the coastal desert of southern Peru where sediment-laden river water is used for irrigation. An adapted facies classification is used to deduce a generalised stratigraphical sequence of the valley bottom sediments. Chronological constraints from radiocarbon dating and archaeological finds are used to reconstruct sedimentation rates for fossil to recent irragric anthrosols. Actualistic case studies are used to quantify present-day irrigation sedimentation. The investigations result in a clarification of the sedimentological and geomorphic history of this valley and a quantification of irrigation-related sedimentation. Irragric anthrosols date back more than 3500 years and provide direct evidence for the beginning of irrigation agriculture in this region. It is concluded that: (i) the up to approximately 4 m thick fine-grained sediments in the Palpa Valley bottom totaling a volume of 21.4 Mio. m³ are a result of long-lasting human impact and have to be considered as artefacts of prehistoric and historic irrigation agriculture in the hyperarid coastal desert; (ii) the fine-grained sediments represent a geoarchive which holds information on the history of irrigation agriculture as well as information on possible natural disturbance by extreme fluvial events; (iii) the identification of irragric anthrosols has implications for archaeological and paleoenvironmental reconstructions.     

Changes in agrophysical properties of floodplain soils under different anthropogenic loads

Agrophysical properties of alluvial soils were studied in the floodplains of the Oka River and the small rivers of Besputa (the Oka tributary) and Pol’noi Voronezh (the Voronezh tributary). The properties of the soils under different land use types (plowland, hayfield, pasture, and meadow) were compared. The features and degrees of alteration of the properties of the floodplain soils under different uses were determined. The greatest changes in the properties were found for saturated alluvial meadow soils of the Oka River floodplain under plowland. In these areas, strong degradation of the physical status of the soils was noted: compaction of the plow and subplow soil layers, an increase in the content of coarse aggregates and clods, changes in the porespace structure, and a decrease in the soil water permeability. It was shown that the soils of small river floodplains were sensitive to anthropogenic loads. In saturated alluvial soddy soils of the Besputa River floodplain, the soil water permeability decreased because of their compaction under the impact of cattle grazing. Saturated alluvial meadow soils of the Pol’noi Voronezh River floodplain were resistant to anthropogenic loads. Only a tendency towards an increase in the topsoil bulk density was observed under the impact of cattle grazing.     

Geomorphology, pedology and sedimentology of the Deoha/Ganga–Ghaghara Interfluve, Upper Gangetic Plains (Himalayan Foreland Basin) — Extensional tectonic implications

Regional mapping of soils helped to identify and map 24 soil-geomorphic units on the Deoha/Ganga–Ghaghara Interfluve in the Upper Gangetic Plains (Himalayan Foreland Basin). On the basis of luminescence ages soil-geomorphic units can be grouped into five members of a Morphostratigraphic Sequence with ages of ≤ 1.7 ka, 1.8–3.6 ka, 4.6–6.4 ka, 6.8–10 ka and > 10 ka. Except for two units with sandy parent material, all the members with loamy parent materials show systematic increase in the degree of soil development from Member QGMS-I to V. Major pedogenic processes are salinization, alkalinization, illuviation, calcrete development and gleying, and degradation of some micromorphological features is observed in the oldest soils.Regional mapping and dating of soils show that the Interfluve between the Deoha/Ganga–Ghaghara rivers is bounded by longitudinal faults, along the bounding rivers. The major longitudinal faults trend N–S or NNE–SSW in the northern region; turn N–S in the central region and take easterly to SEE direction in the south, giving the Interfluve a curvilinear shape. Strike of a set of six transverse extensional normal faults changes from approximately E–W to NEE–SWW in the southernmost region of the Interfluve. Downthrown sides are to the south and to the east in northern region and western region, respectively.Due to the activity of different segments of various transverse faults during a probably dry sub-humid to semi-arid climatic period of 10–5 ka, terminal fans were deposited on the downthrown blocks. Thus, role of extensional tectonics in an overall compressional regime is significant. Also, tilting of smaller blocks leading to the shifting away of large rivers seems to be an additional control on the distribution of soils and sedimentation on the Interfluve.     

Erosion rates and nutrient losses affected by composted cattle manure application in vineyard soils of NE Spain

Land preparation for mechanisation in vineyards of the Anoia–Alt Penedès region, NE Spain, has required major soil movements, which has enormous environmental implications not only due to changes in the landscape morphology but also due to soil degradation. The resulting cultivated soils are very poor in organic matter and highly susceptible to erosion, which reduces the possibilities of water intake as most of the rain is lost as runoff. In order to improve soil conditions, the application of organic wastes has been generalised in the area, not only before plantation but also every 3–4 years at rates of 30–50 Mg ha^− 1 mixed in the upper 30 cm.These organic materials are important sources of nutrients (N and P) and other elements, which could reduce further fertilisation cost. However, due to the high susceptibility to sealing of these soils, erosion rates are relatively high, so a higher nutrient concentration on the soil surface increases non-point pollution sources due to runoff.The aim of this study is to analyse the influence of applied composted cattle manure on infiltration, runoff and soil losses and on nutrients transported by runoff in vineyards of the Alt Penedès–Anoia region, NE Spain. In the two plots selected for the analysis, composted cattle manure had been applied in alternate rows 1 year previous to the study. In each plot soil surface samples (0–25 cm) were taken and compared to those of plots without manure application. The study was carried out at laboratory scale using simulated rainfall. Infiltration rates were calculated from the difference between rainfall intensity and runoff rates, and the sediment and total nitrogen and phosphorus were measured for each simulation. In addition, the influence of compost was investigated in the field under natural rainfall conditions by analysing the nutrient concentration in runoff samples collected in the field (in the same plots) after seven rainfall events, which amount different total precipitation and had different erosive character.Compost application increases infiltration rates by up to 26% and also increases the time when runoff starts. Sediment concentration in runoff was lower in treated (13.4 on average mg L^− 1) than in untreated soils (ranging from 16.8 to 23.4 mg L^− 1). However, the higher nutrient concentration in soils produces a higher mobilisation of N (7–17 mg L^− 1 in untreated soils and 20–26 mg L^− 1 in treated soils) and P (6–7 mg L^− 1 in untreated soils and 13–19 mg L^− 1 in treated soils). A major part of the P mobilised was attached to soil particles (about 90% on average) and only 10% was dissolved. Under natural conditions, higher nutrient concentrations were always recorded in treated vs. untreated soils in both plots, and the total amount of N and P mobilised by runoff was higher in treated soils, although without significant differences. Nutrient concentrations in runoff depend on rainfall erosivity but the average value in treated soils was twice that in untreated soils for both plots.     

Assessing soil erosion and control factors by the radiometric technique in the Boussouab catchment,Eastern Rif,Morocco

In the Eastern Rif of N Morocco, soil conservation is seriously threatened by water erosion. Large areas of soil have reached an irreversible state of degradation. In this study, the ¹³⁷Cs technique was used to quantify erosion rates and identify the main factors involved in the erosion process based on a representative catchment of the Eastern Rif. To estimate erosion rates in terms of the main factors affecting soil losses, samples were collected taking into account the lithology, slope and land use along six selected transects within the Boussouab catchment. The transects were representative of the main land uses and physiographic characteristics of that Rif sector. The reference inventory for the area was established at a stable, well preserved, matorral site (value of 4250 Bq m^− 2). All the sampling sites were eroded and ¹³⁷Cs inventories varied widely (between 245 and 3670 Bq m^− 2). The effective soil losses were also highly variable (between 5.1 and 48.8 t ha^− 1 yr^− 1). Soil losses varied with land use. The lowest average values were on matorral and fallow land (10.5 and 15.2 t ha^− 1 yr^− 1, respectively) but much higher with alfa vegetation or cereal crops (31.6 and 27.3, respectively). The highest erosion rate was on a badland transect at the more eroded part of the catchment, with rates exceeding 40 t ha^− 1 yr^− 1 and reaching a maximum of 48.8 t ha^− 1 yr^− 1.The average soil losses increased by more than 100% when the slope increased from 10° (17.7 t ha^− 1 yr^− 1) to 25° (40. 8 t ha^− 1 yr^− 1). Similar results were obtained when comparing erosion rates in soils that were covered by matorral with respect to those under cultivation. Lithology was also a key factor affecting soil loss. Soils on marls were more erodible and the average erosion rates reached 29.36 t ha^− 1 yr^− 1, which was twice as high as soils on the glacis and old fluvial terraces (average rates of 14.98 t ha^− 1 yr^− 1). The radiometric approach was very useful to quantify erosion rates and to examine the pattern of soil movement. The analysis of main erosion factors can help to promote rational soil use and establish conservation strategies in the study area.     

A mid–late Holocene flood record from the alluvial reach of the Mahi River, Western India

Flooding of rivers in India is linked with the peak monsoons. Investigating the linkage between monsoonal patterns and flood history of various rivers is therefore of fundamental importance in the Indian context. In the present study, the slackwater deposits in the alluvial reaches of the Mahi river basin, western India have been documented. These occur in the ravines incised during the early Holocene on an alluvial surface comprising sediments of Late Pleistocene age. The slackwater deposits occur at elevations up to 20 m from the present river level and extend to about 500 m inland. The carbonate rich sediments forming the ravine cliffs have provided bank stability and the dissections in the ravines have helped in the accumulation of slackwater deposits due to backflooding of the floodwater from the main channel. Recent gullies have incised the sediments and exposed deposits related to major flood events. The best exposures of slackwater deposits have been observed at Dodka. The sediment succession of the slackwater deposits is dominated by bedsets and laminasets of silt and sand separated by colluvial sediments. Four events of flood deposition occurred during the mid to late Holocene. Two units of slackwater deposits, SWD 2 and 4 have been dated by IRSL at 4.6 ± 1 ka and 1.7 ± 0.5 ka. The stratigraphy of these deposits indicates that the first two slackwater units (SWD1 and SWD2) have resulted due to flooding in a regime of intense monsoon. The other two units, however, represent extreme high magnitude floods in a period of low average precipitation.     

Late Quaternary alluvial fans and paleosols of the Kangra basin,NW Himalaya: Tectonic and paleoclimatic implications

The paper describes Late Quaternary pedosedimentary sequences of the alluvial fans from the Kangra basin of NW Himalayas for tectonic and paleoclimatic implications. In the proximal part of the Kangra basin three coalescing alluvial fans, namely Rait-Rihlu fans (~ 65 km²), Kangra fans (~ 200 km²), and Palampur fans (~ 170 km²) from west to east evolved due to reactivation of longitudinal and transverse faults and climatic changes during the Late Quaternary. The fans are characterised by subsidence of Rait-Rihlu fans, uplift of Kangra fans and tilting of Palampur fans. The thick (~ 90 m) pedosedimentary sequences exposed along the rivers characterise the dominant formative processes over the fans. The stream flow sediments dominate the Rait-Rihlu fans, whereas the debris flow sediments dominate the Kangra and Palampur fans. The fan sequences are also marked by the formation of strongly developed paleosols on loess (L1–L3 loess paleosols) and weakly developed paleosols on fluvial deposits in response to the tectonics and climate change in NW Himalayas.     

Spatial and temporal variation of muddy floods in central Belgium, off-site impacts and potential control measures

Numerous villages in the European loess belt are confronted with floods caused by runoff from agricultural land. Seventy-nine percent of the municipalities in central Belgium experienced at least one muddy flood during the last decade. Of these flooded municipalities, 22% have been affected more than 10 times during this period. Twenty municipalities have been selected for a detailed analysis. A database of 367 locations affected by muddy floods has been compiled, and the connectivity between cultivated areas and inhabited zones could be assessed for 100 flooded locations. Roads and drainage network facilitate runoff transfer between cultivated and inhabited areas in 64% of cases. Three types of areas producing muddy floods have been identified: hillslopes (1–30 ha) without thalweg where runoff is generally dominated by sheet flow; small catchments (10–300 ha) characterised by runoff concentration in the thalweg and medium catchments (100–300 ha) with multiple thalwegs dominated by concentrated runoff. About 90% of muddy floods are generated on hillslopes and in small catchments. A critical area–slope threshold for triggering muddy floods has been computed for hillslopes. A logistic regression shows that muddy floods are generated in small and medium catchments with 99% probability after 43 mm rainfall. Rainfall depths required to trigger muddy floods are lower in May and June (25 ±12 mm) than between July and September (46 ± 20 mm), because of different surface conditions (crusting, roughness and crop cover). Each year, muddy floods lead to a total societal cost of 16 × 10⁶–172 × 10⁶ € in central Belgium, depending on the extent and intensity of thunderstorms and monetary values damaged. Recent datasets suggest that the phenomenon is becoming more frequent in central Belgium, because of land consolidation, urban sprawl and expansion of row crops, sown in spring, at the expense of winter cereals. The huge costs induced by muddy floods justify the installation of erosion control measures. It is suggested to install a grassed buffer strip at the downslope edge of cultivated hillslopes to protect houses and roads. In small and medium catchments, it is preferred to install a grassed waterway and earthen dams in the thalweg.     

Natural and Anthropogenic Changes in the Soils and Environment of the Moskva River Floodplain in the Holocene: Pedogenic,Palynological, and Anthracological Evidences

Several series of well-developed paleosols of different ages have been examined on the Moskva River floodplain. In the beginning of the Holocene, forest-steppe biomes were widespread in this area, and dark-humus (Black) soils with stable humate humus and without features of textural differentiation predominated on the floodplain. The presence of meadow-steppe vegetation communities during this period is confirmed by the results of palynological and anthracological analyses. The lower paleosol in section RANIS 2 is represented by the deep humus horizon with ¹⁴C dates from 5500 to 8400 BP and the carbonate-accumulative horizon; it also contains large and deep tunnels of burrowing animals typical of chernozems. Wood charcoal is absent, and pollen of Artemisia and Chenopodium species predominates. Paleosols of the second half of the Holocene are represented by gray-humus and soddy-podzolic soils (Luvisols). In these soils and in the alluvial sediments, beginning from the Subboreal period, pollen of trees predominates; there are abundant charcoal of spruce and burnt spruce needles. In that time, forest-steppe and broadleaved forest biomes on the floodplain were replaced by southern taiga biomes. The second half of the Holocene is also specified by the human impacts on the local landscapes. Palynological and anthracological data attest to the large-scale burning of forests for pastures in the Bronze Age and, later, for cropland. The paleosol of the Iron Age is enriched in humus. It contains tunnels of burrowing animals related to the stage of anthropogenic meadows. It also contains pyrogenic calcite. The recent centuries have been characterized by extremely high floods triggered by the human activity; they have been accompanied by the fast accumulation of coarse-textured alluvial sediments and the formation of weakly developed alluvial soils.     

Use of fallout Cs in investigations of overbank sediment deposition on river floodplains

River floodplains have been recognised as important sinks for storing suspended sediment and associated contaminants mobilised from the upstream catchment. However, information on contemporary rates of overbank sedimentation is difficult to obtain using conventional methods. Measurements of the ¹³⁷Cs content of floodplain sediments provide an alternative approach to obtaining; estimates of medium-term rates (ca. 40 years) of overbank sediment deposition. The ¹³⁷Cs approach requires only a single site visit and minimum sample preparation. Furthermore, it is capable of providing information on spatial patterns of sediment deposition on floodplains, which is needed to improve our understanding of the processes involved in overbank flow and sediment deposition. This paper reviews the basis for using ¹³⁷Cs measurements in floodplain sedimentation studies and presents improved procedures for interpreting ¹³⁷Cs profiles in floodplain sediments and for obtaining estimates of sedimentation rates from single measurements of the total. ¹³⁷Cs inventories of bulk sediment cores. The results obtained from a case study undertaken on the floodplain of the River Stour, Dorset, UK, are presented.     

Hydrological pathway and source area of nutrient losses identified by a multi-scale monitoring in an agricultural catchment

The objectives of the study were to identify principal hydrological pathways and source areas of N and P losses by multi-scale monitoring and to estimate total nutrient losses from the catchment. An agricultural catchment with rain-fed agriculture and irrigated paddy fields in subtropical China was monitored with regularly sampling, together with intensive sampling during and after rain storms. Regular weekly sampling showed that the N concentrations in the overland flows from the upland and paddy fields were higher than those from the streams, but lower than those in the subsurface waters. The N concentration, on average, was 10.0 mg L^− 1 in the well and 1.7 mg L^− 1 in the spring water, the former was 10.2 times as high as that in the stream waters (1.0–1.5 mg L^− 1). Nitrogen and P in the overland flows originated dominantly in particulate forms from the uplands (over 70%) and in dissolved forms from the paddy fields. Inorganic N and P dominated in the streams and subsurface waters. The intensive sampling allowed us to establish flow-nutrient concentration relationships and to extrapolate nutrient losses during rainstorms without regular sampling. The extrapolation increased the estimated nutrient losses by about 30% to 50%. The average total nutrient losses within three water years were estimated as 21 kg N ha^− 1 yr^− 1 and 1 kg P ha^− 1 yr^− 1, accounting for 9.5% and 1.4% of chemical N and P fertilizers applied to the catchment after subtracting the nutrient inputs with irrigation and rainfall. The estimation showed that paddy fields were as important as the uplands in terms of nutrient losses. These results suggest that control of soil erosion and excessive irrigation could be effective to reduce nutrient export through overland flow and subsurface flow.     

Use of landslide-dammed lake deposits and pollen tracing techniques to investigate the erosional response of a small drainage basin in the Loess Plateau, China, to land use change during the late 16th century

A major landslide that occurred in 1569 in the Huangtuwa gully catchment within the Rolling Loess Plateau region of China, resulted in the creation of a landslide-dammed lake at the outlet of the small 0.1 km² tributary valley of the Houxiaotan Gully. All the sediment transported to the outlet of this catchment was deposited in the lake. After about 30 years the dam failed and the lake deposits were dissected as the stream cut down to its former base level. Substantial remnants of the sediment deposits that accumulated over the ca. 30 year period are, however, preserved as terraces near the outlet of the catchment and a vertical section through these sediment deposits was investigated using stratigraphic and pollen tracing techniques. Individual flood couplets could be clearly distinguished and these permitted the establishment of a chronology for the sediment deposits and the estimation of the sediment yields associated with individual events and individual years. Pollen analysis undertaken on samples collected from the individual flood couplets also provided information on the variation of the pollen content of the sediment and the proportion of Artemisia pollen during the period represented by the deposits. Interpretation of the information assembled from the sediment section has made it possible to reconstruct the erosional history of the Houxiaotan catchment during the 31 year period following the landslide. The average sediment yield of the catchment in the late 16th century was very similar to its present-day sediment yield. The sediment yield from the catchment and the relative contribution of the inter-gully areas, as compared to the gully system, declined immediately after the landslide as a result of abandonment of the cultivated land within the catchment. The restoration of cultivation in the catchment after about 17 years resulted in an increase in sediment yield from ca. 9000 t km^− 2 yr^− 1 to ca. 30,000 t km^− 2 yr^− 1 and a substantial increase in the proportion of sediment contributed by the cultivated inter-gully areas. Scope exists to apply a similar approach to the sediment deposits that accumulated in other former landslide-dammed lakes within the Rolling Loess Plateau region of China, in order to develop an improved understanding of the erosion history of the region.     

Denitrification potential of intermittently saturated floodplain soils from a subtropical perennial stream and an ephemeral tributary

Denitrification has the potential to remove excess nitrogen from groundwater passing through riparian buffers, thus improving water quality downstream. In regions with markedly seasonal precipitation, transient stream flow events may be important in saturating adjacent floodplain soils and intermittently providing the anaerobic conditions necessary for denitrification to occur. In two experiments we characterised the denitrification potential of soils from two contrasting floodplains that experience intermittent saturation. We quantified under controlled laboratory conditions: 1) potential rates of denitrification in these soils with depth and over time, for a typical period of saturation; and 2) the influences on rates of nitrate and organic carbon. Treatments differed between experiments, but in each case soil-water slurries were incubated anaerobically with differing amendments of organic carbon and nitrate; denitrification rates were measured at selected time intervals by the acetylene-block technique; and slurry filtrates were analysed for various chemical constituents. In the first experiment (ephemeral tributary), denitrification was evident in soils from both depths (0-0.3 m; 0.3-1.1 m) within hours of saturation. Before Day 2, mean denitrification rates at each depth were generally comparable, irrespective of added substrates; mean rates (Days 0 and 1) were 5.2 ± 0.3 mg N kg dry soil⁻¹ day⁻¹ (0-0.3 m) and 1.6 ± 0.2 mg N kg dry soil⁻¹ day⁻¹ (0.3-1.1 m). Rates generally peaked on Days 2 or 3. The availability of labile organic carbon was a major constraint on denitrification in these soils. Acetate addition greatly increased rates, reaching a maximum in ephemeral floodplain soils of 17.4 ± 1.8 mg N kg dry soil⁻¹ day⁻¹ on Day 2: in one deep-soil treatment (low nitrate) this overcame differences in rates observed with depth when acetate was not added, although the rate increase in the other deep-soil treatment (high nitrate) was significantly less (P ≤ 0.01). Without acetate, peak denitrification rates in this experiment were 6.9 ± 0.4 and 2.8 ± 0.2 mg N kg dry soil⁻¹ day⁻¹ in surface and deep soils, respectively. Differences in rates were observed with depth on all occasions, despite similar initial concentrations of dissolved organic carbon (DOC) at both depths. Levels of substrate addition in the second experiment (perennial stream) more closely reflected natural conditions at the site. Mean denitrification rates were consistently much higher in surface soil (P ≤ 0.001), while the source of water used in the slurries (surface water or groundwater from the site) had little effect on rates at any depth. Mean rates when all treatments retained nitrate were: 4.5 ± 0.3 mg N kg dry soil⁻¹ day⁻¹ (0-0.3 m depth); 0.8 ± 0.3 mg N kg dry soil⁻¹ day⁻¹ (0.3-1.0 m); and 0.6 ± 0.1 mg N kg dry soil⁻¹ day⁻¹ (1.8-3.5 m). For comparable treatments and soil depths, denitrification potentials at both sites were similar, apart from higher initial rates in the ephemeral floodplain soils, probably associated with their higher DOC content and possibly also their history of more frequent saturation. The rapid onset of denitrification and the rates measured in these soils suggest there may be considerable potential for nitrate removal from groundwater in these floodplain environments during relatively short periods of saturation.     

Soils of floodplains in arid regions of Inner Asia (the Zavkhan River,Mongolia)

The environmental conditions of soil formation and the diversity and classification position of soils developing on the Zavkhan River floodplain are considered, and the morphogenetic and agrochemical properties of these soils are characterized. It is shown that the conditions of soil formation on the floodplain of the Zavkhan River are specified by the mountainous topography, the effect of the large Mongol Els sand massif, the character of the alluviation processes, the groundwater level and salinity, and the regime of floods. The position of the floodplain in the system of altitudinal zones largely dictates the character of the soil cover pattern. In terms of the new Russian soil classification system, the soils studied belong to three trunks, four orders, and seven types: stratified humus alluvial soils, light-humus alluvial soils, light-humus quasigley alluvial soils, light-humus stratozems, and solonchaks. The soils of floodplain ecosystems in arid regions are characterized by low fertility. For their efficient use for pasturing and crop growing, the ecologically balanced differentiated application of manure, mineral fertilizers (NPK), and some microelements is required.