Scenario File

The graphical user interface (GUI) allows the user to select which scenario she would like to run. Each scenario is defined by a specific scenario file in the SCENARIOS directory. The scenario file specifies:

• the name of the scenario
• the dependent variable (currently only land cover)
• the watershed in which to run the scenario
• the year in which the starting map was created
• the maps required for the scenario
• the types of the above maps (e.g. impacts map, land cover, etc.)
• the number of values the dependent variable can assume
• the number of independent variables, i.e. the columns in the table of multinomial logit coefficients
• the logit coefficients of the Transition Probability Matrix (TPM)

An example scenario for the Little Tennessee River Basin uses historical transitions for both public and private lands over the period 1975--1986. The dependent variable is land cover and the year of the original map is 1980. The following maps are required:

LAYER   slandcover80.r901rcm    cover
LAYER   spubprivate.r90rcm      matrix
LAYER   sslope.r90m             slope
LAYER   selevation.r90m         elevation
LAYER   spopden80.r90m          indep
LAYER   sdistfranklin.r90m      indep
LAYER   sdistroads.r90m         indep
IMPACT  saspect.r90m            aspect
IMPACT  shyd.r90m               hydro

The first column is the type of map layer (either standard map LAYER or impacts map IMPACT), the second column is the name of the map and the third column is the type of map ( cover is a land cover map, matrix determines which table of coefficients is to be used, indep are general independent variables and slope, elevation, aspect and hydro are specific independent variables). Land cover can change to one of three cover types and there are six rows of coefficients:

# Private Lands ( 1975-1980 )                                       
#       slope    elevation  popdens    disttown   distroads intercept
1 1     0.0       0.0        0.0         0.0        0.0        0.0
1 2    -0.125    -0.00163    0.0017     -0.0019    -0.0242    -0.2845
1 3    -0.10794  -0.0025    -0.0001     -0.00533   -0.0114     1.623
2 1    -0.0028    0.0012    -0.0034      0.0066    -0.064     -1.446
...

The first column is the starting land cover type and the second column is the ending land cover type. The transition probability matrix and the multinomial logit equations are discussed in Section 3.2.