TauDEM 计算 Topographic Wetness Index

根据 TauDEM 的 TWI方法，需要两个数据：slp 坡度，sca 单位汇水面积/Specific Catchment Area. 而坡度计算又需要先填洼；

填洼 PitRemove

mpiexec -n <number of processes> PitRemove -z <demfile> -fel <felfile> [ -4way ][ -depmask depmaskfile]

• demfile: Input elevation grid 输入高程格网
• depmaskfile: depression mask file(Optional input) 可选的洼地掩膜
• felfile: Output elevation grid with pits filled 填洼之后的高程格网文件
• -4way: 4 directions, ie. N, S, E or W neighbors

计算坡度（+流向，D8FlowDir ）

mpiexec -n <number of processes> D8FlowDir -fel <felfile> -p <pfile> -sd8 <sd8file>

• felfile: Pit filled elevation input data 已经填洼的高程输入文件

• pfile: D8 flow directions output 输出的D8流向数据
• sd8file: D8 slopes output 生成的D8 坡度数据

或DinfFlowDir (+流向，taudem中TWI基于此流向算法)

mpiexec -n <number of processes> DinfFlowDir -fel <felfile> -ang <angfile> -slp <slpfile>

• felfile: Pit filled elevation input data 已经填洼的高程输入文件
• angfile: Dinf flow directions output 输出的Dinf算法流向数据
• slpfile: Dinf slopes output 基于Dinf算法的坡度数据

AreaDinf 计算SCA（Dinf算法）

mpiexec -n <number of processes> AreaDinf -ang <angfile> -sca <scafile> [ -o <outletfile>][ -wg ] [ -nc][ -lyrname ] [ -lyrno <layer number>]

• angfile: Input Dinfflow directions grid 输入的流向格网

• scafile: Output Dinf contributing area grid 输出的集水面积格网

• outletfile: input outlets file (OGR readable dataset)(optional) 可选|流域出口输入文件

• wgfile: Input weight grid (optional) 可选|权重格网

• nc: Flag for edge contamination(optional)可选|

• layer name: OGR layer name if outlets are not the first layer in outletfile (optional) 可选|

• layer number: OGR layer number if outlets are not the first layer in outletfile (optional) 可选|

  Layer name and layer number should not both be specified.

计算TWI

mpiexec -n <number of processes> TWI -slp < slpfile> -sca <scafile > -twi <twifile >

• slpfile: input slope file 输入的坡度数据文件

• scafile: input specific catchment area file 输入的单位汇水面积文件

  A grid of specific catchment area which is the contributing area per unit contour length. This should have units of length (area per contour width). It may be the output of the multiple flow direction D-Infinity contributing area function in which case the function by default (without an input weight grid) scales the contributing area in number of cells by the cell size to produce specific catchment area.

  If D8 or some other contributing area evaluated using the number of cells is used here it should first be scaled by cell size to give specific catchment area in length units.

• twifile: output topographic wetness index file