The following options are available for IM:

0  -	2DDI standard ADCIRC
1  -  3D ADCIRC with VS solution
2  -	3D ADCIRC with DSS solution (not currently active)
10 - 	2DDI standard ADCIRC with 2D transport
ABCDEF  -	2DDI ADCIRC configured as discussed below.  ABCDEF represents a single 6 digit integer.  If ABCDEF = 111111, solutions should be very close to the standard ADCIRC.  The digites in ABCDEF trigger the following code configurations:

A = 1 - Kolar & Gray, lateral stress in GWCE
A = 2 - 2 part, flux based lateral stress in GWCE (nonsymmetric), corrected in v44.17
A = 3 - 2 part, velocity based lateral stress in GWCE (nonsymmetric), corrected in v44.17
A = 4 - 2 part, flux based lateral stress in GWCE (symmetric), new option
A = 5 - 2 part velocity based symmetric lateral stress in GWCE (symmetric), new option
B = 1 - non conservative advection in GWCE
B = 2 - conservative version 1 advection in GWCE
B = 3 - conservative version 2 advection in GWCE
C = 1 - velocity based lateral stress in Momentum Eqs. (nonsymmetric)
C = 2 - flux based lateral stress in Momentum Eqs. (nonsymmetric)
C = 3 - velocity based lateral stress in Momentum Eqs. (symmetric), new option
C = 4 - flux based lateral stress in Momentum Eqs. (symmetric), new option
D = 1 - non conservative advection in Momentum Eqs.
D = 2 - conservative version 1 advection in Momentum Eqs.
D = 3 - conservative version 2 advection in Momentum Eqs.
E = 1 - Original (incorrect) are integration in Momentum Eqs.
E = 2 - Correct area integration in Momentum Eqs.
F = 1 - fully consistent left hand side matrix in GWCE
F = 2 - lumped left hand side matrix in GWCE

The parameter Tau0 in the fort.15 file now behaves as:
IF Tau0 >= 0; spatially constant Tau0
IF Tau0 < 0; set Tau0max = abs(Tau0) and use the spatially varying Tau0SpaVar
     IF DEPTH > 200   Tau0SpaVar = 0.005;
     IF 200 > DEPTH >= 1/Tau0max, Tau0SpaVar = 1/DEPTH;
     IF 1/Tau0max > DEPTH  Tau0SpaVar = Tau0max


The lateral eddy viscosity parameter (sometimes called ESL, in the code EVM, in the theory report Eh) in the fort.15 file now behaves as:
IF Eh >=0; spatially constant lateral eddy viscosity
IF Eh < 0; Smagorinski spatially varying lateral eddy viscosity with the leading coefficient = abs(Eh).  Lynch reports using a leading coefficient value of 0.28.


FYI the Smagorinski closure looks like:
Eh = coeff x grid size ^2 x sqrt((dU/dx - dV/dy)^2 + (dV/dx + dU/dy)^2)
I set  grid size^2 = element area