River flow mass exponents with fractal channel networks and rainfall     

Brent M. Troutman  Thomas M. Over   《Advances in water resources》2001,24(9-10)

An important problem in hydrologic science is understanding how river flow is influenced by rainfall properties and drainage basin characteristics. In this paper we consider one approach, the use of mass exponents, in examining the relation of river flow to rainfall and the channel network, which provides the primary conduit for transport of water to the outlet in a large basin. Mass exponents, which characterize the power-law behavior of moments as a function of scale, are ideally suited for defining scaling behavior of processes that exhibit a high degree of variability or intermittency. The main result in this paper is an expression relating the mass exponent of flow resulting from an instantaneous burst of rainfall to the mass exponents of spatial rainfall and that of the network width function. Spatial rainfall is modeled as a random multiplicative cascade and the channel network as a recursive replacement tree; these fractal models reproduce certain types of self-similar behavior seen in actual rainfall and networks. It is shown that under these modeling assumptions the scaling behavior of flow mirrors that of rainfall if rainfall is highly variable in space, and on the other hand flow mirrors the structure of the network if rainfall is not so highly variable.  相似文献   

EVOLUTIONAL CHARACTERISTICS OF HYPER－CONCENTRATED FLOW IN BRAIDED CHANNEL OF THE YELLOW RIVER     

QI Pu  LI Wenxue 《国际泥沙研究》1996,(3)

ＥＶＯＬＵＴＩＯＮＡＬＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＨＹＰＥＲ－ＣＯＮＣＥＮＴＲＡＴＥＤＦＬＯＷＩＮＢＲＡＩＤＥＤＣＨＡＮＮＥＬＯＦＴＨＥＹＥＬＬＯＷＲＩＶＥＲ￥ＱＩＰｕ；ＬＩＷｅｎｘｕｅ（Ｓｅｎｉｏｒｅｎｇｉｎｅｅｒ，ＩｎｓｔｉｔｕｔｅｏｆＨｙ...  相似文献   

Meanders caused by hyperconcentrated water flow: An example from the loess plateau,China     

Xu Jiongxin 《地球表面变化过程与地形》1993,18(8):687-702

This paper describes meandering alluvial rivers with mean annual suspended-sediment concentrations of more than 100 kgm^?3 on the Loess Plateau, China, and explains their formation as caused by the effect of hyperconcentrated water flow. When the river is dominated by hyperconcentrated flow, the rate of energy expenditure required for sediment transport declines significantly. Accordingly, the river channel adjusts itself to a lower channel gradient by increasing the river length, resulting in a meandering channel. Since the stable transportation of sediment by hyperconcentrated flow is dependent on river channel boundary conditions, the latter play an important role in the formation of meanders of this kind. The paper also discusses the conditions for the discrimination of meandering and braided rivers in this area.  相似文献   

Experimental analysis of reservoir release wave routing in upland boulder bed rivers     

D. J. Gilvear 《水文研究》1989,3(3):261-276

Reservoir release wave routing during 33 controlled reservoir releases, along 15 upland boulder bed river channel reaches, on five different regulated rivers were monitored to assess the importance of river channel roughness and reservoir release magnitude on reservoir release wave speeds. Wave speeds varied between 0.52 and 3.01 m s^?1. Reservoir release wave translation, steepening, and attenuation occurred. With high channel roughness values reservoir release wave arrival speed is retarded in comparison to peak stage and wave steepening occurs, but with a reduction in channel roughness reservoir release wave front arrival is accelerated producing attentuation. The threshold between reservoir release wave front attenuation and steepening occurs at a pre-release discharge/channel width of approximately 0.1, an index of channel roughness. The paper also demonstrates, via comparison of observed and calculated reservoir release wave speeds on the River Washburn, Yorkshire, the difficulty of accurately predicting flood wave movement in upland boulder bed channels using existing prediction equations. The calculated values, however, revealed systematic error with pre-release discharge and reservoir release magnitude. Apparently the equations fail to account for the effects of high channel roughness together with pressure gradient forces, induced by rapid rates of stage change on the rising limb of reservoir releases. In order to accurately predict reservoir release wave movement in regulated rivers, this paper demonstrates that hydraulic studies need to be undertaken and pre-release discharges prescribed to determine desired reservoir release wave routing behaviour. Manipulation of the reservoir release pattern at the dam alone, cannot dictate reservoir release wave front form downstream or wave speed.  相似文献   

Resonant period and Q of the Celtic Sea and Bristol Channel     

R.A. Heath 《Estuarine, Coastal and Shelf Science》1981,12(3):291-301

  相似文献   

Spatial and temporal trend of sewage pollution indicated by coprostanol in Macao Estuary,southern China   总被引：1，自引：0，他引：1  

Peng X  Zhang G  Mai B  Min Y  Wang Z 《Marine pollution bulletin》2002,45(1-12):295-299

Bottom sediments and a ²¹⁰Pb dated sedimentary core in Macao Estuary were quantitatively analyzed with GC-MS for coprostanol and other sterols. Higher coprostanol concentrations were detected at Port Interior and Lower Qianshan River, indicative of serious sewage pollution from densely populated Macao Island and Zhuhai City. However, very low concentrations of coprostanol were detected around Coloane Island as well as Port Exterior and Maliuzhou River except sites adjacent sewage outlets. Coprostanol pollution in Macao Estuary originates mainly from locally direct discharge of untreated wastewater. The concentrations of coprostanol in ZJ-9 were mainly in range of 150–280 ng/g with an average of 210 ng/g for more than 20 years from early 1970s to early 1990s. However, it increased obviously since 1993, and reached the highest in 1995–1996. However, a sharp decrease of coprostanol concentration from 470 to 31 ng/g after 1996 was observed corresponding to the first wastewater treatment plant in Taipa Island going into action.  相似文献   

Characterization of beryl (aquamarine variety) from pegmatites of Minas Gerais,Brazil   总被引：2，自引：0，他引：2  

R. R. Viana  H. Jordt-Evangelista  G. Magela da Costa  W. B. Stern 《Physics and Chemistry of Minerals》2002,29(10):668-679

Eight samples of the beryl variety aquamarine were selected from four pegmatites in the Governador Valadares and Araçuaí regions in northeastern Minas Gerais State, Brazil. These samples were fully characterized by chemical analysis, infrared and UV-visible spectroscopy, thermal analyses, and high-temperature X-ray diffraction (from room temperature up to 800 °C). Several physical and chemical properties of beryl were found to depend on the amount of water and ions residing in the structural channels. The thermal expansion coefficients from room temperature to about 800 °C are temperature-independent, with αa ? ?3.2 × 10^?6 ° C^?1 and αc ? ?8.7 × 10^?6 ° C^?1. The contraction of both a and c unit-cell parameters with increasing temperature and the shift of the infrared band centered at about 1200 cm^?1 were tentatively ascribed to interactions between channel water and the silicate rings.The color of beryl seems to be dictated by the relative proportions of Fe³⁺ in the octahedralsites and of fe²⁺ in the channels. Thus, deep-blue samples have little Fe³⁺, whereas greener samples have more Fe³⁺ or less channel Fe²⁺.  相似文献   

The dynamics of a channel-fed lava flow on Pico Partido volcano, Lanzarote     

Duncan Woodcock  Andrew Harris 《Bulletin of Volcanology》2006,69(2):207-215

A short length of channel on Pico Partido volcano, Lanzarote, provides us the opportunity to examine the dynamics of lava flowing in a channel that extends over a sudden break in slope. The 1–2-m-wide, 0.5–2-m-deep channel was built during the 1730–1736 eruptions on Lanzarote and exhibits a sinuous, well-formed channel over a steep (11° slope) 100-m-long proximal section. Over-flow units comprising smooth pahoehoe sheet flow, as well as evidence on the inner channel walls for multiple (at least 11) flow levels, attest to unsteady flow in the channel. In addition, superelevation is apparent at each of the six bends along the proximal channel section. Superelevation results from banking of the lava as it moves around the bend thus causing preferential construction of the outer bank. As a result, the channel profile at each bend is asymmetric with an outer bank that is higher than the inner bank. Analysis of superelevation indicates flow velocities of ~8 m s^–1. Our analysis of the superelevation features is based on an inertia-gravity balance, which we show is appropriate, even though the down-channel flow is in laminar flow. We use a viscosity-gravity balance model, together with the velocities calculated from superelevation, to obtain viscosities in the range 25–60 Pa s (assuming that the lava behaved as a Newtonian liquid). Estimated volume fluxes are in the range 7–12 m³ s^–1. An apparent down-flow increase in derived volume flux may have resulted from variable supply or bulking up of the flow due to vesiculation. Where the channel moves over a sharp break in slope and onto slopes of ~6°, the channel becomes less well defined and widens considerably. At the break of slope, an elongate ridge extends across the channel. We speculate that this ridge was formed as a result of a reduction in velocity immediately below the break of slope to allow deposition of entrained material or accretion of lava to the channel bed as a result of a change in flow regime or depth.  相似文献   

CHANNEL SHRINKAGE AND ITS INSTABILITY IN THE LOWER YELLOW RIVER1     

Jianguo CHEN  Wenhao ZHOU  Anjun DENG 《国际泥沙研究》2006,21(1)

From the mid 1980s through the late 1990s, the channel of the lower Yellow River experienced serious shrinkage, which has decreased the flood conveyance of the channel and the sediment carrying capacity of the flow, raised the water levels of floods, and, thus, severely threatened the safety of flood control along the river. The completion of Xiaolangdi Dam in 1999 could help mitigate the channel shrinkage problem, but the situation has not changed yet. This paper analyses the characteristics, mechanisms, and conditions resulting in channel shrinkage, points out channel instabilities, and puts forward approaches of channel rehabilitation.  相似文献   

RIVER MORPHOLOGY AND CHANNEL STABILIZATION OF THE BRAHMAPUTRA RIVER IN BANGLADESH     

ZHOU Wenhao  CHEN Jianguo 《国际泥沙研究》1998,(4)

１ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅＢｒａｈｍａｐｕｔｒａＲｉｖｅｒｏｒｉｇｉｎａｔｅｓｆｒｏｍｔｈｅＪｉｍａｙａｎｚｈｏｎｇｇｌａｃｉｅｒａｔｔｈｅｎｏｒｔｈｆｏｏｔｏｆｔｈｅＨｉｍａｌａｙａＭｏｕｎｔａｉｎｓｉｎＳｏｕｔｈＴｉｂｅｔ,Ｃｈｉｎａ．Ｉ...  相似文献