Mathematical Model and FORTRAN IV Program for Computer Simulation of Deltaic Sedimentation

Abstract

DELTASIM is a FORTRAN IV program for simulating deltaic sedimentation at a single river-channel mouth. A sediment-laden river flowing into a tideless, currentless marine basin is modeled as a plane jet discharging horizontally at the ocean surface. A velocity field is calculated using equations for open-channel and plane-jet flow. Sediment behavior is treated statistically; nominal sediment particles are traced along trajectories from the mouth as they spread laterally and settle vertically. The rate of sediment accumulation is calculated for each cell of a horizontal accounting grid. Input parameters include channel dimensions, water and sediment discharge, grain-size distribution and bottom topography. Experiments with a static simulation model illustrate the depositional variation produced by changes in grain size, river depth, and slope. The depositional area is narrow in plan view; in elevation, foreset slopes are a function of grain-size and hydraulic parameters, and are normally less than 10. A dynamic model permits a delta platform to build forward during several time increments, nominal particle trajectories adjusting automatically to the position of the delta lip. Experiments illustrate the formation of bars building transversely across the river mouth and the development of submerged levees close to the mouth at the margins of the main flow.

The computer program runs on an IBM System/360 model 67. Graphic displays in the form of CALCOMP plots form an important part of the program output.