Modeling Circulation and Mixing in Tidal Wetlands of the Santa Ana River

The tidal wetlands of the Santa Ana River in Orange County, California are a combination of engineered flood control channels and partially restored salt marshes. The tidal channels extend several kilometers inland with depths comparable to the amplitude of the tides which force circulation, roughly one meter. As is typical of tidal wetlands, there is extensive wetting and drying of sand-bars and mudflats which is a challenge to resolve with numerical models. This paper reports on the application of an unstructured-grid version of an explicit, high-resolution, monotonicity preserving Godunov-type finite volume scheme to solve depth-integrated equations and predict circulation and mixing. Finite volume methods have proven advantageous for applications involving surges and shocks in terms of conservation, monotonicity, stationarity properties, but little has been reported on tidal applications. The paper finds that predictions of water level and velocity at a number of monitoring stations compare well with field measurements, and model predictions of a dispersing dye cloud compare well with measured values when physically meaningful mixing coefficients are used. The model accurately predicts the flooding and drying mudflats without loss of fluid mass, but artificial dilution of dissolved scalars is predicted at the wet/dry interface. The model uses a mall time step consistent with the CFL condition and this contributes towards its ability to resolve sharp fronts and impulse loads.

Language

  • English

Media Info

  • Media Type: Print
  • Features: Figures; References;
  • Pagination: pp 751-769
  • Monograph Title: Estuarine and Coastal Modeling

Subject/Index Terms

Filing Info

  • Accession Number: 01005977
  • Record Type: Publication
  • ISBN: 0784407347
  • Files: TRIS
  • Created Date: Oct 14 2005 1:45PM