Tools Requiring ArcView’s Spatial Analyst (Delineation Tools):

The following tools are related to watershed delineation and are in the extension "MassGIS Watershed Delineator" (watdelin.avx). This extension is dependent on the ESRI Spatial Analyst extension version 1.1 or above. This meanas that if Spatial Analyst is not loaded when the MassGIS Watershed Delineator is loaded, the MassGIS extention will try to load it. When both are loaded, the Spatial Analyst will not be able to be unloaded (it will have a hollow check mark next to it) until the MassGIS Watershed Delineator extension in unloaded first

Please not that if you are using Spatial Analyst 1.0 or 1.0a, the Watershed Analyst tools will not run. Aside from upgrading Spatial Analyst to v. 1.1, the ArcView GIS 3.2 Setup will also update ArcView Spatial Analyst 1.0/1.0a to 1.1 and ArcView Network Analyst 1.0/1.0a to 1.0b when the ArcView GIS installation location includes these earlier versions.

The watershed delineation along the centerline is done in two parts. The first part of the delineation is done using an underlying flow direction grid. This delineation occurs in the subbasin that the user clicked in. The rest of the delineation uses the centerline to trace upstream and accumulate the upstream USGS subbasins which already exist. The watershed delineation that is not along the centerline, however (the upland and downland delineation, and the raindrop tool), use only the flow direction grid and do not use the USGS subbasins boundaries at all. A slight discrepancy may be seen close to the subbasin boundary.

Note: When performing watershed analysis, it pays to zoom in very close to the area of interest. For the delineations, there is a 30m snap to the centerline and a 4 cell (40 meter) snap to the underlying grid as the default. These defaults can be modified by the user. The centerline snap would be changed through the "Change Snap Tolerance for Finding Route" menu choice under the MassGIS-Hydro menu. The snap to the accumulation grid for the delineation would be changed through the "Change Snap Tolerance for Delineation" menu choice under the MassGIS-Hydro menu. If the user is trying to delineate on the centerline and a tiny watershed is drawn when a big one is expected, the point clicked may have been outside the snap range. Try zooming in closer to place the point more accurately, increasing the snap tolerance for delineation, or clicking in a slightly different spot. Be aware, however, that increasing the snap tolerance above 40 meters will likely cause errors (because of polygon subtraction that is occuring, with a built in tolerance of 40 meters).

Note on Grids: Centerlines were systematically extended to a degree outside the state of Massachusetts. However, delineation may not work in all areas outside Massachusetts due to grids which may not extend that far. The grids can be drawn up ("A" button, Watershed Data, choose the specific watershed, Flow Direction Grid) to determine whether they exist in the area of interest. Once all the watersheds are completed we will try to go back and extend these grids to cover the entire centerline outside Massachusetts, provided the grids are available.

The "Upstream Watershed for Point" tool

Application: Delineates a watershed for a point. Runs "UpstreamWatershed" script. The point will snap to the centerline network if it is within 30 meters. If the point does not snap then the watershed will be delineated only from the underlying DEM grid. If the point snaps, then the watershed within the subbasin is delineated from the underlying DEM grid, but the upstream subbasins are accumulated using an upstream trace on the centerline network. Route theme must be added from the "A" button.
Prerequisites: ArcView’s Spatial Analyst extension must be installed. If it is not, the user is warned. The centerline route theme must be active, and must be the only active route theme.
User Action: User clicks on the centerline in the View with the mouse.
End Result: A shapefile called finalpoly.shp is created. The extent is changed at the end of processing to be the extent of this finalpoly.shp. The subbasins theme is also shown.
Defaults: Snap to route is 30m (for the upstream trace part of the delineation. Snap to route for grid delineation is 40m.
Notes: Themes needed for the analysis will be added to the View during processing and then deleted from the View once the final shapefile is made.

The "Upstream Watershed for Points in Batch Mode" tool

Application: Delineates a watershed for each selected point in a point event theme. If none are selected, all points are delineated. Runs "BatchDelineation" script. This could be a button and not a tool, since clicking in the View is not strictly needed. To keep the tool within the dropdown list, however, the user is requested to click anywhere in the View to start off the process.
Prerequisites: The centerline route theme must be in the View and active. The point event theme must be in the View. The point event theme need not come from the A button. These are the only 2 allowable active themes.
User Action: If the point event theme is not active, the user will be asked to pick out the point event theme from a list of themes in the View. The user is told that the output files will be created in the working directory and this directory is printed. The user can cancel to change this path. The user is asked whether they would like the final shapefiles to be called w0.shp, w1.shp… with consecutive numbers, or whether an id item (which can be alphanumeric) in the point event file should be used (i.e. wa3.shp, wb3d.shp)…The user is asked whether certain fields should be included in the final watershed shapefile’s attribute table. Currently these fields are possible: 

The event id of the point event that the watershed was delineated from

The route id of that point event

The measure along the route of that point event

The area in sq. meters of the final watershed

The perimeter in meters of the final watershed

The area in sq. miles of the final watershed

The area in acres of the final watershed

The perimeter in miles of the final watershed

The user is asked whether final delineation shapefiles should be kept in the View as themes (For large point event tables which are delineated i.e. 400 points, the user may not wish all the final themes to remain in the View).

End Result: A shapefile for each point in the point event theme is created.
Defaults: The output shapefiles are put into the working directory shown in the Project/Properties menu. The user has the chance to cancel out and change this directory.
Notes: Batch delineation is only available for point event tables at this time. If "too many routes" are found, or a route is not found, the route snap tolerance should be altered. 1 meter is fine for point event tables and is the recommended snap tolerance in this case. 

The "Upstream Watershed for Line" tool

Application: Delineates a watershed for a stretch of stream. Runs "GetTwoPoints" script. The point will snap to the centerline network if it is within 30 meters. If the point does not snap then the watershed will be delineated only from the underlying DEM grid. If the point snaps, then the watershed within the subbasin is delineated from the underlying DEM grid, but the upstream subbasins are accumulated using an upstream trace on the centerline network.
Prerequisites: ArcView’s Spatial Analyst extension must be installed. If it is not, the user is warned. The centerline route theme must be active, and must be the only active route theme.
User Action: User clicks in the View with the mouse. Route theme must be added from the "A" button.
End Result: Three shapefiles are created: wash1.shp and wash2.shp are the delineations from each point. A shapefile called finalpoly.shp is created which is the subtraction of wash1.shp and wash2.shp. The extent is changed at the end of processing to be the extent of this finalpoly.shp. The subbasins theme is also shown.
Defaults: Snap to route is 30m (for the upstream trace part of the delineation). Snap to route for grid delineation is 40m.
Notes: Themes needed for the analysis will be added to the View during processing and then deleted from the View once the final shapefile is made.

The "Upland Watershed for Polygon" tool

Application: Delineates an upland watershed for a polygon (question: "What is the area that drains to this polygon(i.e. a pond)?" Runs "UpstreamWatershed" script.
Prerequisites: ArcView’s Spatial Analyst extension must be installed. If it is not, the user is warned. The centerline route theme must be active, and must be the only active route theme. Route theme must be added from the "A" button.
User Action: User will be asked to click inside the polygon of the shapefile to use in the delineation. User will also be asked which theme is the polygon shapefile.
End Result: A shapefile called finalpoly.shp is created. The extent is changed at the end of processing to be the extent of this finalpoly.shp.
Defaults: 
Notes: Themes needed for the analysis will be added to the View during processing and then deleted from the View once the final shapefile is made. User is advised to bring up the USGS Topographic maps under the "A" button’s Images menu choice to verify the delineation. Also try the raindrop tool to verify that points inside the delineated area drain to the polygon, and that points outside the delineated area do not drain to the polygon.

Also note: This tool is best for polygons that are not on the centerline, such as parking lots, agricultural fields, or very small ponds, and which result in small delineation areas. To delineate a pond which is part of the centerline, it would be best to use the point delineation tool and click at the pond’s outlet. 

The "Downland Watershed for Point" tool

Application: Delineates a downland watershed for a polygon (question: "Where does the water drain from this polygon(i.e. a parking lot)?" Runs "UpstreamWatershed" script.
Prerequisites: ArcView’s Spatial Analyst extension must be installed. If it is not, the user is warned. The centerline route theme must be active, and must be the only active route theme. Route theme must be added from the "A" button.
User Action: User will be asked to click inside the polygon of the shapefile to use in the delineation. User will also be asked which theme is the polygon shapefile.
End Result: A shapefile called finalpoly.shp is created. The extent is changed at the end of processing to be the extent of this finalpoly.shp.
Defaults:
Notes: Themes needed for the analysis will be added to the View during processing and then deleted from the View once the final shapefile is made. User is advised to bring up the USGS Topographic maps under the "A" button’s Images menu choice to verify the delineation. Also try the raindrop tool to verify that points inside the delineated area drain from the polygon, and that points outside the delineated area do not drain from the polygon.

Also note: This tool is best for polygons that are not on the centerline, such as parking lots, agricultural fields, or very small ponds, and which result in small delineation areas. To delineate a pond which is part of the centerline, it would be best to use the point delineation tool and click at the pond’s outlet.

The "Raindrop Path" tool

Application: The raindrop path tools uses the flow direction grid to figure out the path that a raindrop would take over the landscape. Runs "Raindrop" script.
Prerequisites: ArcView’s Spatial Analyst extension must be installed. If it is not, the user will be warned. . The centerline route theme must be active, and must be the only active route theme. Route theme must be added from the "A" button.
User Action: User clicks in the View with the mouse
End Result: A graphic is drawn on the screen, a black dot for the initial raindrop, and a yellow path for the flowpath. Ignore the notes in the bottom left, the program is generating these and I don’t know what they mean!
Defaults:
Notes: Themes needed for the analysis will be added to the View during processing and then deleted from the View once the final shapefile is made.

What is that tool to the right of the drop down delineation menu? It’s the contour tool supplied by the Spatial Analyst extension, not by the MassGIS Watershed Analyst. Read the documentation that comes with ESRI’s Spatial Analyst extension for a discussion of how to use this tool. 

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Last Updated 3/22/2000
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