Paraglacial response of steep,sediment‐mantled slopes to post‐‘Little Ice Age’ glacier recession in the central Swiss Alps     

A. M. Curry  V. Cleasby  P. Zukowskyj 《第四纪科学杂志》2006,21(3):211-225

This research assesses the morphological consequences of recent (post‐‘Little Ice Age’) paraglacial reworking of valley‐side sediment mantles in the European Alps. It aims to identify the extent and conditioning factors of slope adjustment at sites in the Swiss Alps, model the temporal pattern, and assess the rates of sediment reworking involved. Gully systems have cut into steep, high‐level lateral moraines, and debris cones have accumulated downslope. Debris flow is the dominant agent of sediment transfer. Factors controlling the extent of this activity include moraine slope gradient, relief and moisture availability. Gullies appear to have reached their maximum dimensions within ca. 50 yr of deglaciation, after which gully relief is reduced by removal of inter‐gully slopes and gully infilling (within 80–140 yr). On the most recently deglaciated terrain, minimum erosion rates average ca. 95 mm yr^?1 since gully initiation, greatly exceeding ‘normal’ erosion rates in other environments. Mean annual accumulation of a single debris cone since ice retreat was calculated to be ca. 30 mm yr^?1. Implications of these findings are applied to patterns of paraglacial sediment‐mantled slope adjustment, conceptualising paraglacial landscape response in terms of a sediment release exhaustion model, and paraglacial landform succession. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

A tracer‐based assessment of hydrological pathways at different spatial scales in a mesoscale Scottish catchment     

C. Soulsby  P. Rodgers  R. Smart  J. Dawson  S. Dunn 《水文研究》2003,17(4):759-777

Geochemically based hydrograph separation techniques were used in a preliminary assessment to infer how runoff processes change with landscape characteristics and spatial scale (1–233 km²) within a mesoscale catchment in upland Scotland. A two‐component end‐member mixing analysis (EMMA) used Gran alkalinity as an assumed conservative tracer. Analysis indicated that, at all scales investigated, acidic overland flow and shallow subsurface storm flows from the peaty soils covering the catchment headwaters dominated storm runoff generation. The estimated groundwater contribution to annual runoff varied from 30% in the smallest (ca 1 km²) peat‐dominated headwater catchment with limited groundwater storage, to >60% in larger catchments (>30 km²) with greater coverage of more freely draining soils and more extensive aquifers in alluvium and other drift. This simple approach offers a useful, integrated conceptualization of the hydrological functioning in a mesoscale catchment, which can be tested and further refined by focused modelling and process‐based research. However, even as it stands, the simple conceptualization of system behaviour will have significant utility as a tool for communicating hydrological issues in a range of planning and management decisions. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Effect of the duration and direction of storm movement on infiltrating planar flow with full areal coverage     

V. P. Singh 《水文研究》2002,16(7):1479-1511

Using kinematic wave equations, analytical solutions are derived for flow due to a storm moving up or down an infiltrating plane and covering it completely. The storm duration is assumed in two ways. First, the plane is covered everywhere for the same duration by the storm. Second, the plane is covered in a linearly decreasing manner from the beginning of its coverage of the plane to the other end of the plane. By comparing the flow due to this storm with that due to a stationary storm of the same duration, the influence of storm duration, direction and velocity on flow hydrograph is investigated. It is found that storm movement has a pronounced effect on runoff hydrograph. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

VELOCITIES OF PRECURSOR SOLITON GENERATION IN SINGLE LAYER FLOW   总被引：3，自引：0，他引：3  

徐肇廷  史峰岩  楼顺里 《中国海洋湖沼学报》1997,15(2):130-136

ImODUcrIONThegeneratingveodtyofprecmeorsolitonswasstudiedbyGrimshawetal.(l986),Wu(l987)andbeetal.(1989).TheydidnotgivetherelationbeweenthegeneratingvelocitiesandtopographyintenSityandthereexistSanunknownparameterh,inthetheoryofboetal.(l989),sotheprevioustheorycannotprediCtthegeneratingvelodtAs.ThisfurtherstudyonthetheoryofXuetal.(l996)ahetoconstIUCtatheoryonthegeneratingvefodtiesofsinglelayerflowfondbytopography.InSeCtion2,thernassandenergyoftheprecursorsolitongenerationaredetendnedint…  相似文献   

A Miocene coarse volcaniclastic mass-flow deposit in the Shimane Peninsula,SW Japan: product of a deep submarine eruption?     

Kazuhiko Kano 《Bulletin of Volcanology》1996,58(2-3):131-143

 A subaqueous volcaniclastic mass-flow deposit in the Miocene Josoji Formation, Shimane Peninsula, is 15–16 m thick, and comprises mainly blocks and lapilli of rhyolite and andesite pumices and non- to poorly vesiculated rhyolite. It can be divided into four layers in ascending order. Layer 1 is an inversely to normally graded and poorly sorted lithic breccia 0.3–6 m thick. Layer 2 is an inversely to normally graded tuff breccia to lapilli tuff 6–11 m thick. This layer bifurcates laterally into minor depositional units individually composed of a massive, lithic-rich lower part and a diffusely stratified, pumice-rich upper part with inverse to normal grading of both lithic and pumice clasts. Layer 3 is 2.5–3 m thick, and consists of interbedded fines-depleted pumice-rich and pumice-poor layers a few centimeters thick. Layer 4 is a well-stratified and well-sorted coarse ash bed 1.5–2 m thick. The volcaniclastic deposit shows internal features of high-density turbidites and contains no evidence for emplacement at a high temperature. The mass-flow deposit is extremely coarse-grained, dominated by traction structures, and is interpreted as the product of a deep submarine, explosive eruption of vesicular magma or explosive collapse of lava. Received: 10 January 1996 / Accepted: 23 February 1996  相似文献   

Inbank and overbank velocity conditions in an arid zone anastomosing river     

A. David Knighton  Gerald C. Nanson 《水文研究》2002,16(9):1771-1791

Relative to those at sub‐bankfull flow, hydraulic conditions at overbank flow, whether in the channel or on the floodplain, are poorly understood. Here, velocity conditions are analysed over an unusually wide range of flows in the arid zone river of Cooper Creek with its complex system of anastomosing channels and large fluctuations in floodplain width. At‐a‐station hydraulic geometry relationships reveal sharp discontinuities in velocity at the inbank–overbank transition, the nature of the discontinuity varying with the degree of flow confinement and the level of channel–floodplain interaction. However, despite inter‐sectional differences, velocities remain modest throughout the flow range in this low‐gradient river, and the large increases in at‐a‐station discharge are principally accommodated by changes in cross‐sectional area. Velocity distribution plots suggest that within‐channel conditions during overbank flow are characterized by a central band of high velocity which penetrates far toward the bed, helping to maintain already deep cross‐sections. Floodplain resistance along Cooper Creek is concentrated at channel bank tops where vegetation density is highest, and the subsequent flow retardation is transmitted across the surface of the channels over distances as large as 50–70 m. The rough floodplain surface affects flood wave transmission, producing significant decreases in wave speeds downstream. The character of the wave‐speed–discharge relationship also changes longitudinally, from log–linear in the upper reaches to nonlinear where the floodplain broadens appreciably. The nonlinear form is similar in several respects to relationships proposed for more humid rivers, with flood wave speed reaching an intermediate maximum at about four‐fifths bankfull discharge before decreasing to a minimum at approximately Q_2·33. It does not regain the value at the intermediate maximum until the 10 year flood, by which time floodplain depths have become relatively large and broad floodways more active. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Water temperature and conductivity variability as indicators of groundwater behaviour in complex aquifer systems in the south‐east of Spain     

L. Molina  A. Vallejos  A. Pulido‐Bosch  F. Snchez‐Martos 《水文研究》2002,16(17):3365-3378

Groundwater temperature and electrical conductivity logs were applied in this study to gain an understanding of the hydrogeological behaviour of a complex system. This system, compartmentalized by a large number of fractures, which may even cause geothermal anomalies, is that of the Campo de Dalías in the south‐east of the Iberian Peninsula. In addition to this complexity one must consider the different levels with aquifer properties and their varying lithologies, which in some cases are in direct contact with the sea. Vertical sections based upon the various logs allow lateral correlation to be made between the anomalies detected, and provide information on the existence of both ascending and descending vertical flows, and the inflow of sea water into the system. Analysis of environmental isotopes (¹⁸O and D) indicate the areas of recharge with the greatest flow velocity. No seasonal variation in the isotopes was observed, which suggests that the residence time of the groundwater in the aquifer is several years. Radiocarbon dating gave estimates of generally long residence times, although in some sectors it is possible to detect the current recharge based on its tritium content, from rainwater infiltration or seawater intrusion. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Sub-Alfvénic flows in the quiet and recurrent solar winds     

Gong-liang Zhang 《Chinese Astronomy and Astrophysics》1996,20(4):482-486

Observed instances are given in this paper to show that sub-Alfvénic flow can be formed in the quiet and recurrent low-speed solar wind streams. This kind of flow appears in regions with abnormal enhancement of Alfvénic speed and is associated with a specific type of magnetic configuration.  相似文献   

Incorporating ancillary data to refine anthropogenically modified overland flow paths     

Guy D. Duke  Stefan W. Kienzle  Dan L. Johnson  James M. Byrne 《水文研究》2006,20(8):1827-1843

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Simulation of groundwater dynamics in the North China Plain by coupled hydrology and agricultural models     

Tadanobu Nakayama  Yonghui Yang  Masataka Watanabe  Xiying Zhang 《水文研究》2006,20(16):3441-3466

We simulated the effects of irrigation on groundwater flow dynamics in the North China Plain by coupling the NIES Integrated Catchment‐based Ecohydrology (NICE) model with DSSAT‐wheat and DSSAT‐maize, two agricultural models. This combined model (NICE‐AGR) was applied to the Hai River catchment and the lower reach of the Yellow River (530 km wide by 840 km long) at a resolution of 5 km. It reproduced excellently the soil moisture, evapotranspiration and crop production of summer maize and winter wheat, correctly estimating crop water use. So, the spatial distribution of crop water use was reasonably estimated at daily steps in the simulation area. In particular, NICE‐AGR reproduced groundwater levels better than the use of statistical water use data. This indicates that NICE‐AGR does not need detailed statistical data on water use, making it very powerful for evaluating and estimating the water dynamics of catchments with little statistical data on seasonal water use. Furthermore, the simulation reproduced the spatial distribution of groundwater level in 1987 and 1988 in the Hebei Plain, showing a major reduction of groundwater level due mainly to overpumping for irrigation. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献