Tuflow and estry manual Version 3

1.2ESTRY

ESTRY is a powerful network dynamic flow program suitable for mathematically modelling floods and tides (and/or surges) in a virtually unlimited number of combinations.

The program was developed by WBM Oceanics Australia over a period of twenty-five years and has been successfully applied on hundreds of investigations ranging from simple single channel applications to complex quasi-2D flood models. The network schematisation technique used allows realistic simulation of a wide variety of 1D and quasi-2D situations including complex river geometries, associated floodplains and estuaries. By including non-linear geometry it is possible to provide an accurate representation of the way in which channel conveyance and available storage volumes vary with changing water depth, and of floodplains and tidal flats that become operable only above certain water levels.

There is a considerable amount of flexibility in the way the network elements can be interconnected, allowing the representation of a river by many parallel channels with different resistance characteristics and the simulation of braided streams and rivers with complex branching. This flexibility also allows a variable resolution within the network so that areas of particular interest can be modelled in fine detail with a coarser network representation being used elsewhere.

The model is based on a numerical solution of the unsteady fluid flow equations (momentum and continuity), and includes the inertia terms. This capability of modelling tidal flows has the added advantage of enabling the tidal portion of a flood model to be calibrated separately using readily obtainable measurements of the tide levels and flows. Extension of the calibrated tidal model into the floodplain then results in a more accurate flood model in which the flood channels can be calibrated separately against available flood records.

In addition to the normal open channel flow situations, a number of special types of channel are available including:

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  uniform open channel, with or without specified bed gradient;
  
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  subcritical and supercritical flow regimes;
  
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  non-inertial channels;
  
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  multiple circular or rectangular box culverts;
  
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  bridges;
  
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  weir channels for flow across roadways, levees etc;
  
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  user defined structures; and
  
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  uni-directional channels of any type capable of being specified, to allow flow in only one direction.
  

The type of information provided as output by the model for a flood or tide simulation includes the water levels, flows, and velocities throughout the area being modelled for the simulation period. Other information available includes maximum and minimum values of these variables as well as total integral flows (integrated with time) through each network channel.