New models for optimal sewer system design.

Three new models ha-e been developed for the least-cost design of storm sewers. All three models consider the sewers as a system. The basic model designs the crown elevations, slopes, and diameters of the sewers. The sewer system layout is predetermined. Routing is accomplished by lagging the hydrographs by a travel time. Optimization is achieved through a discrete differential dynamic programming technique to produce the least-cost design of the system based on specified cost functions for install ation of the sewers and manholes. The second model is an expansion of the basic model incorporating risk-based damage costs in the design procedure, and the risks for each sewer associated with the least-cost design are also given as part of the design results. The third model is similar to the basic model except that the least-cost sewer layout is also a part of the design result instead of being predetermined. (A) (Microfiche)