摘要:

AbstractA descriptive model for bed material routing in small sand and gravel bedded channels with sequences of pools and armoured riffles was developed. Aspects of the model are demonstrated at Flynn Creek, a 202‐ha, third‐order drainage in the Oregon Coast Range. Assuming that channel geometry, sediment transport competence, and the availability of sediments for transport are all non‐uniform in the downstream direction, the model described bedload transport as occurring in two phases. Phase I involves the transport of fine, predominantly sand‐sized bed materials over stable gravel‐armoured riffles. Phase II occurs at higher flows that can entrain riffle armour and transport riffle sediments, in addition to Phase I sediments. Phase I bedload transport was sampled during three moderate flow events. A power function related Phase I bedload transport to water discharge. The relationship was consistent between storms and between two successive years. Phase II bedload transport, sampled during a 1.8‐yr return period streamflow event in February, 1979, proved non‐uniform in a downstream direction and unsteady over time at a given stream discharge. Transport rates closely correlated with the rapid scour and redeposition of the riffle at the bedload sampling cross‐section; transport peaks corresponded to scour and transport decreased greatly during deposition. The transport of large (>12.5 mm diam.) bed material increased up to 12‐fold du

ISSN:0197-9337    

DOI:10.1002/esp.3290070602

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper describes the morphology, sequential development and general sedimentology of concave‐bank benches on the Murrumbidgee River of southeastern Australia, and also notes their important role in floodplain formation on certain meandering rivers in western Canada. Benches form against the concave bank (cut‐bank) of abruptly curving bends immediately upstream of the point of maximum curvature. As a result of flow deflection against the upstream limb of the convex bank, the channel widens here and produces a zone of expanded flow facilitating flow separation near the upstream limb of the concave bank. Sedimentation within this zone starts with a longitudinal‐shaped bar of medium sand forming a platform isolated even at low flow by a narrow secondary channel against the concave bank. Aggradation of the longitudinal‐shaped bar with fine sand, mud and organic matter permits the establishment of trees. Further sedimentation, particularly around the young trees, results in the formation of a fully developed bench isolated by the secondary channel from the remainder of the floodplain only during high flows. Observations on confined meandering rivers in western Canada provide evidence of substantial floodplain formation by concave‐bank bench accretion, a process distinctly different in character to the more familiar mechanism of lateral point‐bar accretion. Furthermore, the preservation of abundant organic debris means that extensive bench deposits may be a source of locally useful natural gas from within floodplai

ISSN:0197-9337    

DOI:10.1002/esp.3290070603

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractMore than 400 dolines, consisting of collapse sinkholes and closed depressions, occur in Hall and Briscoe Counties, Texas. Of these, at least 36 sinkholes and two depressions formed between 1940 and 1972. Collapse sinks are typically circular and range up to 100 m in diameter and 15 m in depth. Closed depressions are irregularly‐shaped, internally‐drained depressions up to 2.4 km in length. Surface fractures up to 1.5 km in length are associated with certain closed depressions.Karst features are forming as a result of intrastratal dissolution of Upper Permian evaporites, primarily halite and secondarily gypsum. Salt dissolution and overburden collapse are evident from geophysical log cross‐sections and occur at depths ranging from 195 to 275 m. Dissolution is progressing down dip and mean dissolution rates for salt beds in the Hall County area range from 0.29 to 7.73 cm/yr.The valley of the Prairie Dog Town Fork of the Red River is an area of ground‐water discharge for flow systems moving eastward from topographically high areas of the Rolling Plains and from the eastern rim of the High Plains. Halite beds in contact with these waters undergo dissolution. Salt springs and brine seeps, some associated with sinkholes and depressions, occur in the discharge area and indicate that dissolution is an ongoing

ISSN:0197-9337    

DOI:10.1002/esp.3290070604

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe contribution of throughflow to storm runoff is examined using a chemical mixing model. The results predict that throughflow is an important component of storm runoff particularly during the period of stream recession. Supporting hydrological data suggests that a major throughflow input occurs coincident with the stream discharge peak. The two sets of results therefore conflict in the predicted timing of the throughflow response.

ISSN:0197-9337    

DOI:10.1002/esp.3290070605

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractSimple, and locally compound, transverse and barchanoid dunes dominate the 2000 km2Skeleton Coast dunefield in northwestern Namibia/South West Africa. Dune height and spacing are closely correlated (r= 0‐89) and decrease across the dunefield from southwest to northeast, with an accompanying change from transverse to barchanoid ridges and ultimately barchans.The dunes are aligned transverse to the dominant strong south and south southwest onshore winds. Alignment patterns indicate that surface roughness changes between coastal plain and dunes cause dune‐forming winds to swing to the right over the dunes, but resume their original direction beyond.Grain size and sorting vary at three scales: the dune, the dune landscape and through the dunefield. Overall the sands, derived from three localities by deflation from beaches supplied by vigorous longshore drift, become progressively finer and better sorted across the dunefield paralleling changes in dune height and spacing.A statistically significant relationship (r= −0−65) was established between dune spacing and the phi grain size of the coarser fraction of the dune sands, demonstrating the importance of the protective effects of coarse grains, and suggesting that the morphometry of simple transverse dunes may be controlled by the scale of turbulence associated with the threshold wind speed required to move the coarsest fraction of the du

ISSN:0197-9337    

DOI:10.1002/esp.3290070606

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractA new method is proposed for solving a differential equation arising from weathering‐limited development of a valley. Allowance is made for horizontal stratification and overhang can be allowed to develop. The model is applied to the Grand Canyon and comments are included on its relevanc

ISSN:0197-9337    

DOI:10.1002/esp.3290070607

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290070608

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290070610

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290070612

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290070614

出版商:John Wiley&Sons, Ltd    

年代:1982

数据来源: WILEY