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eRAMS Watershed Delineation Tool

 

Abstract

eRAMS watershed delineation tool processes and analyzes Digital Elevation Model (DEM) and DEM-driven rasters to delineate watershed. The core of this tool is TauDEM version 5 (Tarboton, 2013). The executable files of TauDEM were used inside Java platform – Cloud Service Innovation Platform (CSIP) (David et al., 2015), which were called in eRAMS platform. There are three major options such as ‘advanced’, ‘basic’ and ‘watershed extraction’. Most of tools were developed based on 5.0.6 (Tarboton, 2012) except Modified Peucker Douglas, which is based on TauDEM 5.1.2 (Tarboton, 2014) . More detailed information of input and output of TauDEM5 is explained in Tarboton(2013)’s documentation section.

 

Kewords

pit removal, flow direction, flow accumulation, grid analysis, Strahler stream network order, flow path, stream network, Peucker Douglas, outlets, weighted flow accumulation, drop analysis, stream raster, subwatershed, gage watershed, Taudem, CSIP, watershed delineation, watershed extraction

Citation

Kim, J. S., Arabi, M., Patterson, D. (2015). eRAMS watershed delineation tool [Software].

 

User’s guide

eRAMS watershed Delineation tool can be activated by clicking tool icon on the toolset located on the top of the map or clock icon in top right corner of the map as shown in figure 1.

begin

Figure 1. The activation of watershed Delineation Tool.

Figure 2 shows the activated GUI of eRAMS watershed delineation tool. At the top section, user can choose an option such as basic, advanced and watershed extraction. The advanced option lets user run each tool for watershed delineation sequentially. Also, user can customize input file, parameters and the name of ouput file in the advanced option. Basic tool runs every tool in an advanced option automatically. The last option – ‘Watershed Extraction’ tool only runs ‘move outlets’ and ‘gage watershed’ tools with NHDPlusV2 (US EPA, 2015) flow direction raster to extract entire watershed as one shapefile. User can create working directory by clicking ‘Create New Folder’. Output files will be stored in the directory if the folder is chosen in the box next to the ‘Select folder’.

UI

Figure 2. User Interface of Watershed Delineation Tool.

 

Advanced Option

 

Clip DEM (optional)

This tool clips out NHDPlusV2 DEM for the area user defines in the continental US. The unit of DEM is ‘meter’ and it has 30m resolution. The maximum size of the supporting area is 1 square degrees, which covers most of HUC 10. If user has input DEM, it can be uploaded by clicking Project Layers, Spatial Layers, Add Layer, and Add Raster. It should be noted that DEM should be in the projected coordinate system to get correct slope raster. If DEM is not projected, the unit of slope raster will be the unit of height / the unit of X and Y. Also, ‘Stream Network – Drop Analysis’ and ‘Stream Raster – Threshold’ tools accept only rasters in projected coordinate system.

Fill Sinks

‘Fill sinks’ removes pits in DEM to enhance flow delineation in DEM by using ‘pitremove’ module of Taudem5. Figure 3. shows the example of original DEM (left) and  pit-removed DEM (right).

Sink-fill (pit removal ) procedure

Figure 3. The original DEM with sink (left) and the sink-filled DEM (right) (The color scales are not exactly same.).

Optionally, in eRAMS environment, user can burn streams on pits-removed DEM. The rule of burning stream on DEM is to add the maximum elevation to non-stream pixels. It should be noted that DEM should be projected to the coordinate system with consistent X, Y, and height units to get correct slope raster if user wants to upload user’s own DEM.

Compute Flow Direction

With pits-removed DEM, flow direction (out of eight directions) is calculated at each pixel by ‘Compute flow direction’ procedure. This tool uses ‘d8flowdir’ module of Taudem5. The value of 1 in flow direction raster means stream flows to the east direction. The direction increases by 45 degrees counter clockwise as direction value increases by 1. Also, slope raster is created at the same time.The value of slope raster is the maximum slope calculated at each pixel. Figure 4 shows the example of flow direction and slope rasters.

 direction_slope

Figure 4. The flow direction raster (left) and slope raster (right).

Compute Flow Accumulation

Flow accumulation raster shows the total contributing numbers of stream pixels summed at the target pixel based on flow direction raster (8 directions) by using ‘aread8’ module of Taudem5. Eight different colors represent each flow accumulation range (minimum range: red, maximum range: blue) as shown in Figure 5. Also, this raster is recommended to be used as a ground truth for outlets selection for large scale watershed in later step – ‘Move Outlets’.

flow_acc

Figure 5. Flow accumulation raster.

Grid Analysis

This tool outputs three rasters such as the longest flow path raster, total flow paths raster, and grid network order raster as shown in figure 6 by using ‘gridnet’ module of Taudem5. The pixel value of the longest flow path raster represents the length of the longest upstream flow path from the cell. The pixel value of the total flow paths raster shows the total length of the upstream paths from the cell. Total flow paths raster is recommended as a ground truth for outlets selection for mid – large scale watershed in later step – ‘Move Outlets’. The pixel value of the grid network order raster shows the Strahler order number (Strahler, 1952, 1957). Strahler order is 1 for the source flow path. If two flow paths with identical order meets, it increases by one. Otherwise, the order is the highest order out of merged flow paths. If more than two flow paths join, the order is the either 1) the highest order if there is one highest rank stream or 2) one plus the order of the highest rank if there are two or more streams of the highest rank. (Tarboton, 2013).

lngst

Figure 6. The longest flow path (left), the total flow paths (center), and the grid network order (right) rasters.

Stream Network – Modified Peuker Douglas

‘Stream Network – Modified Peuker Douglas’ tool represents stream pixels as value of one. Taudem 5’s original ‘peukerdouglas’ module implemented the stream delineation of Peucker & Douglas'(1975) research. Original ‘peukerdouglas’ module in Taudem 5 turned off the flat regions. This seem to underestimate stream pixels in relatively flat area (Example: the location where river meets lake). Therefore, Taudem 5’s ‘peukerdouglas’ module was edited to include stream pixels in flat area by adapting prior knowledge of flow accumulation. The pixels in flat area with the flow accumulation values larger than the defined threshold was added to the original Peuker Douglas stream pixels. The threshold was determined as the average of flow accumulation on the original Peuker Douglas stream pixels. It is important to include these stream pixels in flat area because the outlet will be moved to stream pixels in later steps. Not enough stream pixel can increase the chance of 1) failing moving outlets to stream pixels 2) moving outlets to stream pixel in unreasonably far distance. Figure 7 and 8 show the comparison between the results from the original and modified Peuker Douglas tool at the location where Colorado River meets Grand Lake & Arapaho Bay in Colorado (figure. 7) and the downstream of Eagle Creek, Indiana (figure 8).  It was found that modified Peuker Douglas tool properly added stream information to the original Peuker Douglas tool. Therefore, we can have more rigorous results in later steps – “Move Outlets” and ‘Weighted Flow Accumulation’, which requires stream raster as an input.

pd_comp2

Figure 7. USGS Hydro NHD national Map (left), stream pixel from original Peuker Douglas tool (center), stream pixels from modified Peuker Douglas tool (right) at Colorado River & Grand Lake & Arapaho Bay.

pd_comp

Figure 8. USGS Hydro NHD national Map (left), stream pixel from original Peuker Douglas tool (center), stream pixels from modified Peuker Douglas tool (right) at Eagle Creek, Indiana.

Also, stream raster from Modified Peuker Douglas tool can be used as a ground truth for the outlet selection, especially for small scale watershed in later step – ‘Move Outlets’. Figure 9 shows the small scale watershed (compared to the size of HUC12 watershed – purple polygons) defined from the outlet chosen on modified Peuker Douglas stream pixels. .

watershed2

Figure 9. Small scale watershed defined by the outlet on a Modified Peuker Douglas stream pixel.

Move Outlets

Next procedure – ‘Move Outlets’ transfers outlet points to stream pixels (modified Peuker Douglas steam pixels) following flow direction. This tool uses ‘moveoutletstostrm’ module of Taudem5. Figure 10 shows the example of moving original outlet (red dot) to the stream pixel (with light blue dot) of modified Peuker Douglas pixels (light blue pixels). This step is highly recommended for the outlet points which are not located on stream pixels.

moveoutlet

 

 

 

 

 

Figure 10. Moving outlet to a stream pixel.

If outlet point shapefile is not available, user can add outlet points on the web map. It should be noted that the location of outlet (even one pixel difference) can make a significant difference in the final watershed delineation results. Therefore, it is highly recommended to zoom in to the maximum scale when choosing outlet points from the ground truth. Also, it is important to use proper ground truth for choosing outlet points. For the delineation of large scale (about the size of HUC12) watershed, the flow accumulation raster is highly recommended for choosing outlet points. If user wants to delineate small scale watershed as shown in figure 8, modified Peuker Douglas stream pixel will be the most suitable ground truth for choosing outlet points since it includes every possible stream skeletons. Figure 11 shows the examples of choosing outlets on flow accumulation and modified Peuker Douglas stream raster.

outlet_on_accoutlet_on_pd

 

 

 

 

 

Figure 11. Example of choosing outlet point (red dot) on flow accumulation raster (left) and modified Peuker Douglas stream raster (right).

Sometimes, there is no ground truth for choosing outlet points (Example: basic option and watershed extraction option). In those cases, it is recommended to use Hydro-NHD layer of USGS National Map in base layer as a ground truth for choosing outlet. In any case, it is highly recommended to move the position of outlet points to relevant location if the final result is not satisfactory.

Weighted Flow Accumulation Area

This tool sums up the number of pixels of weight grid by using ‘aread8’ module of taudem5. By default, modified Peuker Douglas stream raster is used as weight grid, which defines the contribution values of each grid cell. Figure 12 shows the example of the result of weighted flow accumulation area. There is a condition that streams on contributing pixels should eventually flows into the outlets. Therefore, the boundary of this raster will be the watershed to be delineated in later steps. If the result is not satisfactory, please adjust the location of outlet points.

area_wg_1

Figure 12. Example of Weighted Flow Accumulation Area raster.

Stream Network – Drop Analysis

‘Stream Network – Drop analysis’ finds the threshold value for stream raster grid by t-test, which evaluates the significant difference between the first and higher order streams created based on the threshold assumption.  This tool uses ‘dropanalysis’ module of taudem5. The lowest and the highest threshold values for drop analysis were set to each 5 and 1500 pixels. Drop analysis will provide result table as shown in figure 13. The row highlighted by yellow color represents the optimal threshold value, which is the minimum area passing t-test (t value < 2). Also, the table shows related statistics such as number, mean, standard deviation of drops, the ratio of 1st order stream and t values. It should be noted that drop analysis should not be implemented for stream-burned DEM because the drop of the first order stream will be significantly larger than higher order stream.

drop

Figure 13. Drop analysis result and optimal threshold highlighted.

Stream Raster – Threshold

‘Stream Raster – Threshold’ defines stream raster by choosing pixels of the values larger than the given threshold from weighted flow accumulation raster. This tool was created using ‘threshold’ module in taudem5. By default, the threshold is given by drop analysis. However, user can choose other values by clicking another row in drop analysis table if more rigorous or lenient criteria is required. Figure 14 shows the example of stream raster – threshold.

stream3

Figure 14.The example of stream raster.

Extract Streams and Channel Network

This procedure outputs stream network and sub-watersheds as shapefile formats using ‘streamnet’ module of taudem5. The table of stream network shapefile has been updated so that the attributes should be consistent with NHDPlusV2’s file format – plusflowlinevaa.dbf (US EPA, 2015). ‘streamnet’ module creates subwatershed raster, which has unique subwatershed id as digital number (dn) of pixels. By definition, subwatershed drains to each stream network link (Tarboton, 2013). Taudem’s output subwatershed raster was converted to polygon shapefile using python module of gdal – gdal_polygonize.py (Open Source Geospatial Foundation, 2015). Figure 15 shows the example of stream network and subwatershed shapefiles.

stream_subw

Figure 15. The shapefiles of Stream network (left) and subwatersheds (right).

Gage Watershed

This tool delineates the entire watershed for the defined outlet points as a shapefile using ‘gagewatershed’ module in taudem5. The output watershed raster was converted to shapefile using gdal module – gdal_polygonize.py. Figure 16 shows the example of  the watershed delineated by gage watershed tool.

gage

Figure 16. The watershed delineated by gage watershed tool.

Basic Option

The second option of eRAMS watershed delineation tool is ‘basic’. And it executes the procedures in ‘advanced’ option automatically. The input data are DEM and Outlet Points layer. For the simplicity of basic tool, stream burning procedure was excluded in this option. It is highly recommended to use input DEM in a projected coordinate system with consistent X, Y, and height unit. Otherwise, the unit should be assigned to the result slope raster. For example, if input DEM is in geographic coordinate system with X [degree], Y [degree], and Z [meter], the unit of slope raster should be interpreted as [meter/degree]. To fully automate the procedures, two conditions were given. Firstly, the outlet points moves to modified Peuker Douglas stream pixels automatically. Secondly, 10 pixel was used as threshold for ‘stream raster – threshold’ If drop analysis can’t find threshold value (Example: watershed is too small). Therefore, it is advised to check drop analysis result after each running of basic tool. If outlet point shapefile is not available, user can choose any points on the web map. Since there is no ground truth (such as flow accumulation, or modified Peuker Douglas raster) for outlet points before running basic option, user has to use base layer as a reference. It is recommended to use Hydro-NHD layer as a base layer / ground truth for outlet If a user clipped input DEM from NHDPlusV2 DEM by ‘Clip DEM’ tool. Figure 17 shows the types of base layers available in eRAMS platform.

nhd

Figure 17. Hydro NHD layer for a ground truth for outlet selection.

Watershed Extraction Option

This option only runs ‘move outlets’ and ‘gage watershed’ procedures with NHDPlusV2 (US EPA, 2015) flow direction raster. The inputs are “outlet points” and “the area of analysis”, which can be defined by the bounding box, which user created. User can click ‘Define the Area of Analysis’ button shown in figure 18 and draw bounding box (yellow rectangle) as shown in figure 19. The requested service may take approximately 30 seconds. Red dot shows the outlet point user chooses on Hydro-NHD layer. Once user define the outlet points (by uploading shapefile or marking on map) and the area of analysis, the bounding box coordinates are transformed to EPSG:5070 (NAD1983 Conus Albers, the projection of NHDPlusV2 data). Then, NHD flow direction VRT (GDAL, n.d.) was created and clipped for the bounding box. Since direction notations of NHDPlusV2 are different from Taudem5’s, the flow direction values were modified to conform to Taudem5’s standard by gdal_calc.py. To move outlet’s to stream pixels, stream VRT from NHDPlusV2 HydroDEM was created. The threshold value for the extraction of streams from HydroDEM was -100m. After moving outlets to stream pixels, watershed raster was extracted by ‘gage_watershed’ and transformed to polygon shapefile format. It should be noted that the projection of original flow direction (NHDPlusV2 flow direction raster) should be preserved since the re-projection of flow direction raster will decrease the accuracy of flow direction. Figure 20 shows the example of the extracted watershed. If the result of watershed extraction is not satisfactory (example: too small), please adjust the location of the outlets. After extraction of watershed, the area of analysis layer (yellow rectangle) can be removed by clicking ‘Clear all graphic from map’ button as shown in figure 21.

watershed extraction

Figure 18. Watershed Extraction user interface.

ext2

Figure 19. Bounding box for the area of analysis.

ext3

Figure 20. The example of extracted watershed.

clear

Figure 21. Removal of area of analysis layer.

API Notes

Basic
This tool executes the series of watershed delineation procedures automatically. The input data are DEM and Outlet Points layer. Outlet points are moved to stream pixels by default. For stream raster – Threshold procedure in basic tool, threshold was set to 10 pixels if threshold is not found by drop analysis. Optionally, user can clip DEM from NHDPlusV2 DEM (not burned).

Input Parameters

Parameter Type Description
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “dem”, “value”: “dem.tif”}, { “name”: “outlet”, “value”: “outlet_pt.shp”} ] }

Output Parameters

Parameter Type Description
demcoord dat Channel network tree coordinates
demtree dat List of links in channel network tree
dem_fill tif Filled DEM raster
streamnet shp, shx, dbf Channel network shapefile. This file includes from node, to node, and reach code for network analysis.
demw tif Subwatershed raster
gage_watershed tif Watershed boundary raster
gorder tif Strahler order raster
ord tif Strahler order raster for stream cell
PD_stream tif Modified Peuker Douglas stream raster
lngst_path tif The longest flow path raster
dir tif Eight flow direction raster
slope tif Eight direction slope raster
stream tif Thresholded stream raster
subwatershed shp, shx, dbf Subwatershed polygons shapefile
area_wg tif Weighted flow accumulation raster
outlet_moved shp, shx, dbf The moved outlets shapefile
drop txt Drop analysis table. The unit of threshold in drop.txt is pixels. However, drop tables in GUI shows the thrshold with meter units.
watershed shp, shx, dbf watershed boundary
fill_sinks
The application removes pits in input DEM using ‘pitremove’ module of Taudem5.

Input Parameters

Parameter Type Description
DEM raster tiff Digital Elevation Model in tiff format (Project to coordinate system consistent with Z-unit of DEM).
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “dem”, “value”: “dem_input.tif” } ] }

Output Parameters

Parameter Type Description
DEM – pit removed tiff The output DEM is create by filling out sinks of input DEM.
d8flowdir
The application creates (eight direction) flow direction raster and slope raster using ‘d8flowdir’ module of Taudem5.

Input Parameters

Parameter Type Description
DEM – pit removed tiff Digital Elevation Model (pit removed) in tiff format.
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “dem_fill”, “value”: “dem_fill.tif” } ] }

Output Parameters

Parameter Type Description
Flow direction raster tiff The output flow direction raster. Pixel value “1” means the direction of East. And the value of pixel increases by one whenever the direction angle increases by 45 degree to counter-clockwise.
slope raster tiff The output slope raster. The slope value is calculated by dividing the drop by distance.
flow_accumulate
The application creates flow accumulation raster using ‘aread8’ module of Taudem5.

Input Parameters

Parameter Type Description
Flow direction raster tiff Flow direction raster in eight directions.
JSON request JSON JSON file, which defines input parameters.
request = { “metainfo”: { }, “parameter”: [ { “name”: “flow_8_dir”, “value”: “p.tif” } ] }

Output Parameters

Parameter Type Description
Flow accumulation raster tiff The output flow accumulation raster. The value of targe cell is the sum of contributing numbers of pixels, through which stream eventually flows into the target cell.
grid_analysis
The application creates the longest flow path, total length of flow path, and grid network order raster using ‘gridnet’ module of Taudem5.

Input Parameters

Parameter Type Description
Flow direction raster tiff Flow direction raster in eight directions.
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “flow_8_dir”, “value”: “p.tif” } ] }

Output Parameters

Parameter Type Description
Longest flow path raster tiff The value of cell is the length of the longest upstream flow path from the cell.
Total length of flow pah raster tiff The value of cell is the total length of the upstream paths from the cell.
Grid network order tiff Stream order defined by Strahler (1952, 1957)
mod_Peuker_Douglas
The application creates stream raster using the tool – ‘mod_peukerdouglas ‘, which was updated from ‘peukerdouglas’module of Taudem5.

Input Parameters

Parameter Type Description
DEM – pit removed tiff Digital Elevation Model (pit removed) in tiff format.
Flow accumulation raster tiff The value of targe cell is the sum of contributing numbers of pixels, through which stream eventually flows into the target cell.
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “dem_fill”, “value”: “dem_fill.tif” }, { “name”:”flow_acc”, “value”: “ad8.tif” } ] }

Output Parameters

Parameter Type Description
Modified Peucker-Douglas stream raster tiff The pixels of value 1 means that they are either 1) stream defined by Taudem5’s Peuker-Douglas model or 2) flat region with significant flow accumulation.
Taudem5’s PeukerDouglas’ stream pixels.
outlet
The application moves outlet points not on stream to a stream pixel following flow direction raster using “moveoutletstostrm” module of Taudem5. This procedure is highly recommended for the outlet points, which is not on stream pixels.

Input Parameters

Parameter Type Description
outlets shp, shx, dbf shapefile including outlet points.
Flow direction raster tiff When outlet points move, they move following flow direction raster.
Peucker-Douglas stream raster tiff Outlet points will move to the pixels of stream raster.
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “flow_8_dir”, “value”: “p.tif” }, { “name”: “stream”, “value”: “peuker_douglas.tif” }, { “name”: “outlet_shp”, “value”: “outlet_pt.shp” }, { “name”: “outlet_shx”, “value”: “outlet_pt.shx” }, { “name”: “outlet_dbf”, “value”: “outlet_pt.dbf” } ] }

Output Parameters

Parameter Type Description
outlets moved shp, shx, dbf Shapefile including outlet points (optionally moved to stream raster pixels).
w_flow_accumulate
This application sums up the number of contributing stream pixels at target cell using “aread8” module of Taudem5. There is a condition that stream of contributing pixels should eventually flow into the defined outlet points.

Input Parameters

Parameter Type Description
Flow direction raster tiff Flow direction raster in eight directions.
Peucker-Douglas stream raster (optional) tiff Stream raster will be used as weight raster.
outlets shp, shx, dbf Shapefile of outlet points.
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “flow_8_dir”, “value”: “p.tif” }, { “name”: “peuker_douglas”, “value”: “peuker_douglas.tif” }, { “name”:”outlet_shp”, “value”: “outlet_2.shp” }, { “name”:”outlet_shx”, “value”: “outlet_2.shx” }, { “name”:”outlet_dbf”, “value”: “outlet_2.dbf” } ] }

Output Parameters

Parameter Type Description
Weighted flow accumulation raster tiff The cell value of the weighted flow accumulation is the sum of the number of pixels, through which stream flows to the target cell. Another condition is the stream will eventually flows into the outlet points defined.
stream_network
The application evaluates the significant difference between the first and higher order streams created based on the stream threshold assumption using ‘dropanalysis’ module of taudem5. It should be noted that drop analysis should not be implemented for stream-burned DEM because the drop of the first order stream will be significantly larger than higher order stream.

Input Parameters

Parameter Type Description
DEM – pit removed tiff Digital Elevation Model (pit removed) in tiff format.
Flow accumulation raster tiff The value of targe cell is the sum of contributing numbers of pixels, through which stream eventually flows into the target cell.
Flow direction raster tiff Flow direction raster in eight direction.
outlets shp, shx, dbf Shapefile of outlet points
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “dem_fill”, “value”: “dem_fill.tif”}, { “name”: “flow_acc”, “value”: “ad8.tif”}, { “name”: “flow_dir”, “value”: “p.tif”}, { “name”: “outlet_shp”, “value”: “outlet_2.shp”}, { “name”: “outlet_shx”, “value”: “outlet_2.shx”}, { “name”: “outlet_dbf”, “value”: “outlet_2.dbf”} ] }

Output Parameters

Parameter Type Description
Drop analysis table txt Drop analysis evaluates the significant difference by T test between the mean drops of the first and higher order streams created based on the threshold assumption. It finds the minimum threshold which let the model pass the T test.
stream_raster
The application creates stream raster using threshold values and weighted flow accumulation raster with ‘threshold’ tool in Taudem5. Unless input dem is stream-burned, drop analysis tool will provide the optimal threshold value. Also, user can choose customized threshold values in drop analysis table.

Input Parameters

Parameter Type Description
Weighted flow accumulation raster tiff The cell value of the weighted flow accumulation is the sum of the number of pixels, through which stream flows to the target cell. Another condition is the stream will eventually flows into the outlet points defined.
Threshold float The threshold for defining stream. By default, the threshold from drop analysis is used.
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “w_flow_acc”, “value”: “weighted_area.tif” }, { “name”: “threshold”, “value”: extra_list[0][1] } ] }

Output Parameters

Parameter Type Description
Flow Raster Grid tiff The pixels of the values larger than the given threshold are chosen from weighted flow accumulation grid .
extract_stream
This application creates stream network shapefile and sub watersheds raster using ‘streamnet’ module of Taudem5. Each stream segment is defined by the links in stream network and sub-watershed raster is created based on each stream segment. The sub watersheds raster is converted to shapefile by gdal_polygonize.py.

Input Parameters

Parameter Type Description
DEM – pit removed tiff Digital Elevation Model (pit removed) in tiff format.
Flow direction raster tiff Flow direction raster in eight directions.
Flow accumulation raster tiff The value of targe cell is the sum of contributing numbers of pixels, through which stream eventually flows into the target cell.
Stream threshold raster tiff The stream raster of which the pixel values are larger than threshold such as Flow Raster Grid.
Outlets shp, shx, dbf Shapefile of outlet points.
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ {“name”: “flow_dir”, “value”: “p.tif”}, {“name”: “filled_dem”, “value”: “dem_fill.tif”}, {“name”: “flow_acc”, “value”: “ad8.tif”}, {“name”: “src”, “value”: “src.tif”}, { “name”: “outlet”, “value”: “outlet_2.shp”}] }

Output Parameters

Parameter Type Description
Stream network shp The polyline shapefile which describes the link information of streams.
Subwatersheds shp Subwatersheds shapefile. Unique ID numbers are assigned to each subwatershed.
gage_watershed
This application creates entire watershed shapefile for a defined outlet using ‘gagewatershed’ module in Taudem5 and gdal_polygonize.py. The output watershed can be used as a boundary layer for HRU delineation tool.

Input Parameters

Parameter Type Description
Flow direction raster tiff Flow direction raster in eight directions.
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ {“name”: “flow_dir”, “value”: “p.tif”}, {“name”: “outlet”, “value”: “outlet_2.shp”}] }

Output Parameters

Parameter Type Description
Watersheds tiff For the given outlets, entire watershed is delineated by the pixel value 1.
extract_watershed
This application creates entire watershed shapefile for a defined outlet using ‘gagewatershed’ and ‘moveoutletstostrm’ modules in Taudem5 and gdal_polygonize.py. The stream raster was created from NHDPlusV2 hydroDEM assuming pixels, of which the values are less than -100 meters, as stream cells. The user uploaded (defined) outlet will be moved to stream pixels. The NHDPlusV2 flow direction raster will be clipped based on the bounding box user created. The limit of user’s dragging bounding box is 1 squares degrees, which covers most of HUC 10.

Input Parameters

Parameter Type Description
JSON request JSON JSON file, which defines input parameters.
{ “metainfo”: { }, “parameter”: [ { “name”: “outlet”, “value”: “outlet_pt.shp”}, { “name”: “bound_wkt”, “value”: input_list[1][1]}, { “name”: “bound_wkt_2”, “value”: input_list[2][1]} ] }

Output Parameters

Parameter Type Description
Watersheds tiff For the given outlets, entire watershed is delineated by the pixel value 1.

Moved

outlet points

shp The outlets moved to stream pixels.
extract_DEM
This application clips and extracts DEM from NHDPlusv2 DEM. The input is Well Known Text (WKT) in EPSG:4326 (WGS84 geographic coordinate system)

Input Parameters

Parameter Type Description
JSON request JSON JSON file, which defines input parameters.
{“metainfo”: {},”parameter”: [{ “name”: “bound_wkt”,
“value”: input_list[0][1]}]}

Output Parameters

Parameter Type Description
DEM_clip.tif tiff Clipped DEM, the projection is consistent with NHDPlusV2 DEM

 

References:
David, O., Lloyd, W., Arabi, M., Rojas, K. (2015). Cloud Service Innovation Platform User Manual and Technical Documentation [draft].
GDAL (n.d.) GDAL Virtual Format Tutoria, Retrieved from http://www.gdal.org/gdal_vrttut.html
Open Source Geospatial Foundation (2015). gdal_polygonize.py. Retrieved from http://www.gdal.org/gdal_polygonize.html
Peucker, T. K., & Douglas, D. H. (1975). Detection of surface-specific points by local parallel processing of discrete terrain elevation data. Computer Graphics and image processing, 4(4), 375-387.
Strahler, A. N. (1952), “Hypsometric (area-altitude) analysis of erosional topology.” Bull. Geol. Soc. America 63 (1952): 1117-1142.
Strahler, A. N. (1957). Quantitative analysis of watershed geomorphology. Civ. Eng, 101, 1258-1262.
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