An ensemble of analytic tools is used to identify capacity expansion alternatives for the Delaware River dredged-material disposal system. Characteristics of the river and riparian area are stored and analyzed with a geographic information system. Site attractiveness maps produced with these data yield an array of potential expansion sites. The least-costly schedule for acquisition of these sites is identified with branch-and-bound enumeration. For the enumeration, the operation cost of alternative expansion plans is evaluated with a network-flow programming model of the disposal system. (Author).

This paper describes the impacts of potential hydropower retrofits on downstream flow distributions at Lock and Dam No. 8 on the upper Mississippi River. The model used solves the complete Reynolds equations for two-dimensional free-surface flow in the horizontal plane using a finite element solution scheme. RMA-2 has been in continuing use and development at the Hydrologic Engineering Center and elsewhere for the past decade. Although designed primarily for the simulation of hydraulic conditions, RMA-2 may be used in conjunction with related numerical models to simulate sediment transport and water quality. In this study, velocity distributions were evaluated with regard to environmental, navigational and small-boat safety considerations. Aquatic habitat was defined by depth, substrate type and current velocity. Habitat types were quantified by measuring the areas between calculated contours of velocity magnitude (isotachs) for existing and project conditions. The capability for computing and displaying isotachs for the depth-average velocity, velocity one foot from the bottom and near the water surface was developed for this study. The product of this study effort is an application of the RMA-2 model that allows prediction of structural aquatic habitat in hydraulicaly complex locations. Elements of the instream flow group methodology could be incorporated to provide detailed predictions of impacts to habitat quality. Calibration of the numerical model to field measurements of velocity magnitude and direction is also described.

Last year the Hydrologic Engineering Center (HEC) and the Waterways Experiment Station incorporated the results from more than ten years of research and development into a new version of computer program HEC-6: 'Scour and Deposition in Rivers and Reservoirs' (HEC, 1977). Because of the extensive modifications made to HEC-6, an entirely new User's Manual was also prepared. HEC released a Beta Test Version of the program in the fall of 1989, for field testing. Public release of the new version of HEC-6 is scheduled for September 1990. This paper describes the present status of the program as of April 1990, the expanded capabilities, and the improved documentation to be included in the forthcoming release of computer program HEC-6. Keywords: Computer programs; User manuals; Sediment transport modeling; Deposition; One-dimensional mobile boundary model; Rivers; Reservoirs. (CP).