SEED

Description

Performs automatic seeding for delineation of sub-watersheds defined by major tributaries.

Parameters

Name	Type	Length	Value range
Seed File	String	0 -
InputFACCUM: Input flow accumulation channel*	Raster port	1 - 1
InputFDELTA: Input flow delta value channel*	Raster port	1 - 1
Output: Output flow starting cell channel*	Raster port	1 - 1
Port Settings: Resample mode*	Raster port	1 - 1024	Nearest \| Bilinear \| Cubic Default: Nearest
Drainage Threshold	Integer	0 - 1	Default: 10
Seed on Data Set Edge	String	0 - 1	Default: NO
Layer Descriptive Text	String	0 - 1	Default: Seeding Results

* Required parameter

Parameter descriptions

Seed File

Optionally specifies the name of a text file that contains the coordinates of the seeds.

If this file is specified, watershed seeds will be generated at the coordinates listed inside the file. See the Details section for the formatting of the file. If this parameter is not specified, seeds are automatically generated.

InputFACCUM: Input flow accumulation channel

Specifies the flow accumulation channel obtained from the DWCON function. This channel contains a data set in which each cell has been assigned a value equal to the number of cells that flow into it. The input channel must be either 16-bit signed integer or 32-bit real.

InputFDELTA: Input flow delta value channel

Specifies the flow delta value channel obtained from the DWCON function. This channel contains data reflecting the amount of increase in the flow accumulation value in the flow direction. The input channel must be either 16-bit signed integer or 32-bit real.

Output: Output flow starting cell channel

Specifies the output channel to receive the starting cell data. The output channel must be either 16-bit signed integer or 32-bit real.

Port Settings: Resample mode

Specifies the type of image resampling desired.

Supported methods include:

Nearest: nearest neighbor; this is the default value
Bilinear: bilinear interpolation
Cubic: cubic convolution

Drainage Threshold

Specifies the seed threshold value. A watershed will be seeded at every major tributary where the area draining to the tributary, as indicated by the flow accumulation and flow delta value data sets, exceeds the specified threshold.

Seed on Data Set Edge

Specifies whether to build seeds on the data set edge, where the flow accumulation data exceeds the specified threshold.

Available options are:

YES: builds seeds on the data set edges
NO: does not build seeds on the data edges (default)

Layer Descriptive Text

Describes (in up to 56 characters) the contents or origins of the output data.

Details

SEED performs automatic seeding for delineation of sub-watersheds defined by major tributaries.

Six functions make up the drainage network component:

DWCON
DRAIN
OVERLND
PPTABLE
SEED
WTERSHED

To use SEED, you must first run the DWCON function.

For more information about the drainage network functions, see the help for DWCON.

The SEED function inserts "seeds" or "starter cells" at the outflow points of specific watersheds. This seeding is performed automatically.

The results from this function can be used to delineate specific watersheds, using the WTRSHED function.

For some hydrologic applications, it is necessary to divide a watershed into sub-watersheds defined by major tributaries. Sub-watersheds are watersheds in themselves, but are referred to as sub-watersheds in the context of also being part of a large watershed.

SEED has two options:

Watershed seeds are automatically generated

This option automatically produces a "seed" data set. The user must specify a drainage threshold (THRESH). A watershed is seeded at every major tributary where the area draining to the tributary, as indicated by the flow accumulation and flow delta value data sets, exceeds the specified threshold.
Watershed seeds are generated from a text file

In this option, the coordinates of the seeds are contained in a text a file. The format of the text file should be as follows:
```
line 1 :  No. of coordinates
line 2 :  seed_no. x-coord. y-coord.  (separated by spaces)
line 3 :  seed_no. x-coord. y-coord.  (separated by spaces)
  "           "
```
For example, to create a text file of five coordinates and three seeds:
```
5
1 100 200
1 101 200
2 200 30
3 400 500
3 400 501
```
Repeating the seed number is useful to delineate a broad feature such as a dam.

After the execution of SEED, run the WTRSHED function on this "seeded" data set to see the watershed results.

Note: SEED must be executed after the DWCON function.

FACCUM (InputFACCUM) and FDELTA (InputFDELTA) specify the flow accumulation channel and the flow delta value channel, respectively. These channels are obtained by running the DWCON function. FSTART (Output) specifies the flow starting cell output channel to store the results. The input and output channels must be either 16-bit signed integer or 32-bit real.

THRESH (Drainage Threshold) specifies the seed threshold value. A watershed will be seeded at every major tributary where the area draining to the tributary, as indicated by the flow accumulation and flow delta value data sets, exceeds the specified threshold.

EDGES (Seed on Data Set Edge) specifies whether build a seed on the data set edge, where the flow accumulation data exceeds the specified threshold. The default setting is "NO".

TEX1 (Layer Descriptive Text) specifies a description of the output channel. The default is "Seeding Results".

References

Jenson, S.K. and Domingue, J.O. "Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis". Photogrammetric Engineering and Remote Sensing, Vol. 54, No. 11, November 1988, pp. 1593-1600.

Environments	PYTHON :: EASI :: MODELER
Batch Mode	Yes
Quick links	Description :: Parameters :: Parameter descriptions :: Details :: References :: Related