HYDRAULIC GEOMETRY AND STREAM CHANNEL BEHAVIOR: A UNCERTAIN LINK1

ABSTRACT: The at-a-station hydraulic geometry of stream channels can serve as a predictor of alluvial stream channel behavior. This geometry is the empirical relations describing changes in water surface width, mean depth, and mean velocity with changing discharge. The exponent values are correlated with channel morphology and behavior such as scour and fill, flow resistance, bank resistance, and competence. Channel behavior and morphology are apparently related, but some causes for effects are uncertain. Several studies, using empirical and theoretical bases, are reviewed here to illustrate the relation between hydraulic geometry and channel behavior, but the relations are not always consistent. Hydraulic geometry variables are easy to measure and readily available, but they do not always reflect what may be more important ones such as turbulence, the velocity distribution profile, and distribution and cohesion of sediment particles. This paper illustrates some of these problems, provides some solutions, and addresses need for more work to better predict stream channel behavior from hydraulic geometry     

USE OF INCISED CHANNEL EVOLUTION MODELS IN UNDERSTANDING REHABILITATION ALTERNATIVES1

ABSTRACT: Incised channels are caused by an imbalance between sediment transport capacity and sediment supply to the stream. The resulting bed and bank erosion alter channel morphology and stability. Geomorphological models of incised channel evolution can provide guidance in the selection of engineering design alternatives for incised channel rehabilitation. This paper describes how incised channel evolution models may be coupled with a dimensionless stability diagram to facilitate evaluation of rehabilitation alternatives. In combination, the models provide complementary views of channel processes from geomorphic and engineering perspectives.     

广州港出海航道疏浚对珠江口水质影响及预防措施

主要介绍了广州港出海航道疏浚情况及其对珠江口水质影响以及疏浚过程中采取一些预防措施。     

铜鼓航道工程建设对中华白海豚的影响分析

中华白海豚是国家一级重点保护的野生濒危动物，深圳铜鼓航道部分路线会穿越珠江口中华白海豚自然保护区，对白海豚产生不良影响。文中结台白海豚的生态特点，分析了工程对白海豚的影响，并提出了相应的保护对策。     

PERSISTING SEDIMENT YIELDS AND SEDIMENT DELWERY CHANGES1

ABSTRACT: The Buffalo River is a tributary to the Mississippi River in west-central Wisconsin that drains a watershed dominated by agricultural land uses. Since 1935, backwater from Lock and Dam 4 on the Mississippi River has inundated the mouth of the Buffalo's valley. Resurveys of a transect first surveyed across the lake in 1935 and cesium-137 dating of backwater sediments reveal that sedimentation rates at the Buffalo's mouth have remained unchanged since the mid-1940s. Study results indicate that sediment yields from the watershed have persisted at relatively high levels over a period of several decades despite pronounced trends toward less cultivated land and major efforts to control soil erosion from agricultural land. The maintenance of sediment yields is probably due to increased channel conveyance capacities resulting from incision along some tributary streams since the early 1950s. Post-1950 incision extended the network of historical incised tributary channels, enhancing the efficient delivery of sediment from upland sources to downstream sites.     

EVALUATION OF URBAN STREAM CORRIDOR RESTORATION DESIGN ALTERNATIVES USING HEC-21

ABSTRACT: The rehabilitation of urban stream channels and riparian areas involves a potentially large number of design alternatives. When substantial modifications are planned, water surface profile models (e.g., HEC-2) provide a means for a thorough and efficient evaluation of many design variations. The rehabilitation of a reach of Paradise Creek, Idaho, utilized the REC-2 model to verify the appropriateness of a new channel geometry and explore the consequences of variable floodplain geometries and excavation depths. The desirability of habitat diversity, coupled with the constraints of minimized earthwork costs and adequate flow capacity, framed the floodplain design question. The final design geometry was iteratively approached using the HEC-2 model to mimic the existing channel capacity. This modeling framework produces as output computed water surface elevations for the design channel and floodplain under any discharge. Hence, the method provides the means for demonstrating that rehabilitation designs will (or will not) cause increases in flood elevations, an assessment that is generally required for project approval.     

FEE FISHING AREAS IN ILLINOIS1

ABSTRACT: Fishing is a popular form of recreation in the state of Illinois. Despite seemingly endless varieties of fishing opportunities, limited public access, distant location of lakes with respect to population centers, chemical contaminants in some waters, and the desire for species not naturally found in Illinois have engendered an alternate form of recreational land use, the daily fee fishing area. A fee area is any privately controlled body of water or waters where a fee is charged for fishing. Such operations must Low licensed by the state of Illinois. Fee areas are almost entirely comprised of existing man-made impoundments, particularly farm ponds. They are usually stocked on a put and take basis. The most common species utilized in Illinois are carp and channel catfish. Fee areas are concentrated in the southwestern part of the state and near major metropolitan centers. Even though the number of fee areas has declined during the past decade, the role of such operations remains important to the overall picture of fishing in Illinois.     

THE ROLE OF MINIMUM VARIANCE THEORY IN DEFINING THE REGIME CHARACTERISTICS OF THE LOWER NAMOI-GWYDIR DRAINAGE BASIN1

ABSTRACT: While minimum variance theory appears to offer an explanation for the hydraulic behaviour and regularity among channel systems it is not entirely successful in predicting the regime of a channel system. In the case of the Namoi-Gwydir river system the hydraulic variables velocity, depth, width, slope, friction, and shear appear to govern the behaviour and, hence regime of the channels. The significance of sediment load in determining regime could not be assessed.     

HYDROLOGIC EFFECTS OF THE FLOOD ABATEMENT PROGRAM IN SOUTHWESTERN OKLAHOMA1

ABSTRACT: Winter Creek is a tributary of the Washita River in south-western Oklahoma. The Soil Conservation Service installed floodwater retarding structures which controlled runoff from 56 percent of a 33-square-mile (8550-hectare) gaged drainage area. Application of a hydrologic model to the flood peaks indicated that the structural treatment reduced the flood peaks an average of 61 percent. The Winter Creek channel has narrowed and deepened since the structural treatment was applied. The severe bank erosion occurring before treatment has been arrested and sediment yield from the watershed has been reduced 50 to 60 percent. In some reaches of the channel there has been a dense growth of trees in recent years.     

Analysis of the velocity field in a large rectangular channel with lateral shockwave

In this work the authors describe the main characteristics of the velocity field of hydraulic jumps in a very large channel where lateral shockwaves occur. Experiments were carried out at the Coastal Engineering Laboratory of the Water Engineering and Chemistry Department of the Technical University of Bari (Italy). Extensive flow velocity measurements were investigated in order to have a clearer understanding of both hydraulic jump development and lateral shockwave formation in a very large channel. Eight experiments were performed in a 4m wide rectangular channel; the experiments differed in the inlet Froude number F ₀ and the jump type. Seven tests were carried out with undular jumps and one with a roller jump. The flow velocity and the flow free surface measurements were taken using a two-dimensional Acoustic Doppler Velocimeter (ADV) and an ultrasonic profiler, respectively. The experimental results can be summarized as follow: (i) the formation of well developed lateral shockwaves similar to those of oblique jumps were observed; (ii) the comparison of the experimental and theoretical data shows that the classic shockwave theory is sufficiently confirmed in the analyzed range of Reynolds number, taking into account the experimental errors and the difference between the theoretical and experimental assumptions; (iii) the transversal flow velocity profiles in the recirculating zone show a good agreement with the numerical simulations presented in literature in the case of a separated turbulent boundary layer over a flat plate. This conclusion enables us to confirm the hypothesis that the lateral shockwaves in the channel are the result of a boundary layer which, as observed, forms on the channel sidewalls.