Daryl B. Simons

Sediment Transport Capacity of Overland Flow

ABSTRACT OVERLAND flow runoff can be either laminar or turbulent depending on the Reynolds number. The rate of soil erosion may be limited by the sediment transport capacity which depends on the type of flow. Sediment transport equations based on velocity were found to give different results than those based on shear stress. Most of the sediment transport equations developed for turbulent streams should not be applied to soil erosion by overland flow. A general relationship supported by dimensional analysis was derived. The recommended sediment transport capacity relationship can be written as a power function of slope and discharge and the range of exponents was defined from empirical relationships.

Flow Resistance in Vegetated Waterways

ABSTRACT Anew method to determine the flow capacity of a vegetated channel is presented. The method uses the vegetations length and stiffness as parameters. Graphs of field data of Mannings n versus the product VR, velocity times hydraulic radius, can be accurately repro-duced. A table of stiffness values for various types of veg-etation for which flow data were available is included. It is shown that the n —VR method of channel design cur-rently in use is based on the correct premise that n is a function of VR regardless of the relative values of V and R. The limitations of the n —VR method are stated. The advantage of the new method is that it is a numerical method which can be easily incorporated in computer programs for other purposes such as backwater or rout-ing models.

Hydrology, hydraulics, and geomorphology of the Upper Mississippi River system

The Upper Mississippi River system has been modified with locks, dams, dikes, bank revetments, channel modifications, and dredging to provide a nine-foot navigation channel. These activities have changed the rivers characteristics. The historical changes in the hydrologic, hydraulic, and geomorphic characteristics were assessed and related to navigational development and maintenance activities in the Upper Mississippi River system. The hydrologic, hydraulic, and geomorphic features studied include river discharges, stages, sediment transport, river position, river surface area, island surface area, and river bed elevation. Water and sediment transport effects on dredging were also estimated. It was found that the general position of the Upper Mississippi River system has remained essentially unchanged in the last 150 years except for specific man-made developments in the river basin. The stage, velocity, sediment transport, and river and island areas were altered by development of the 2.75-m navigation system. Dredging requirements are strongly related to mean annual water discharge. Years in which water discharges were great were generally the years during which large volumes of sediment needed to be dredged from the channel. The backwater areas are experiencing some deposition. With implementation of erosion-control measures in major tributaries and upland areas, better confinement of disposed dredged materials, and better maintenance practices, the sedimentation and pertinent problems in the main channel, as well as in the backwater areas, may be reduced with time.

Effects of Stream Regulation on Channel Morphology

“The erosion cycle — detachment, transport, deposition — is described by the Second Law of Thermodynamics, which states each system tends to move in the direction of lowest energy. Because of the potential energy of soil (rock) in elevated positions and because of the kinetic energy of flowing water, all soil and water will move, eventually, to the lowest possible level, i.e., the ocean deeps, or to some temporary, intervening basin” (McHenry, 1964, 1969, 1974). The intervening basins, destined to be filled with sediment, include the reservoirs that we have become so dependent upon. We daily enjoy the benefits they provide, not fully realizing that they are continually filling and that, in the not so distant future, many will become useless. It is possible to accelerate or decelerate this process, but the filling is inevitable, given current knowledge. The reservoir’s life is dependent on sediment deposition. The under-standing of, and the ability to predict, both channel and reservoir response processes are extremely important. The rate and magnitude of changes experienced by watersheds and rivers depend on many naturally imposed factors, including floods, changes in the duration of specific flows, droughts, and changes in the water and sediment supply imposed by earthquakes, vertical changes in the earth’s crust, floods, and mass wasting.

Surface coal mining hydrology

A physical-process approach to the planning and design of stable mine drainage systems is presented. Various source control measures useful for minimizing water pollution associated with mining activities are discussed, along with guidelines for selection of appropriate measures considering site-specific conditions. Source control measures discussed include surface protection, mechanical treatment, detention and filtering structures, and water diversion structures. Flow charts depicting design procedures for surface protection measures and diversion channels are included. An overview of dynamic equilibrium concepts applicable to diversion channel design in sandy soils is also presented. Different types of sediment ponds, design considerations, and basic design concepts are introduced in a section pertaining to treatment measures. Reference documents providing detailed design guidelines and methodologies are cited in discussions of the different control measures.