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DSM2 Geo-Referenced Grid

Background

DSM2 input specifies geographically based information such as channel lengths and cross-section distances from the upstream node. However, the geographically referenced node locations or channel outlines are not directly needed for hydrodynamic calculations.

Even though this information is not needed directly, it is very important to keep the geographically referenced information in sync with the input parameters such as channel length and cross-section locations in DSM2 input.

Sacramento - San Joaquin Delta Grid

The original DSM2 grid was based on hand-calculated distances using USGS Quad maps of the Delta (circa 1990). These were done on paper maps, and the original information has been lost.

A PDF version of this grid was created using AutoCAD. However, the node locations in this version are not geo-referenced to any projection system. Nodes and channels were not always placed carefully, as the map was primarily used to identify approximate locations of nodes, channels, and stations.

In the late 1990s or early 2000s, a paper copy of the grid was digitized, resulting in a file containing approximate UTM coordinates of each node. This file was used by the DSM2 Cross-Section Development Program (CSDP) to create representations of DSM2 channels and cross-sections.

CSDP was developed by Brad Tom and Nicky Sandhu based upon specifications written by Ralph Finch in 1998 to derive the cross sections from bathymetry data, which at the time were mostly single beam soundings of depth that were available over many decades in the Delta. This tool is the basis of the current grid in 2000 and the recalibrated grid in 2009. As a by-product of this effort, the node locations and channel outlines were stored in UTM coordinates. Originally, these were not used directly to derive channel lengths, but they were used indirectly in determining the distance of a cross-section from the upstream node of a channel. The DSM2 GIS Reference project, which began in 2018, used CSDP centerlines to determine channel lengths.

CSDP was developed pre-ArcGIS, and with ArcGIS now being fairly standard in DWR, there is a need to provide this geographical information in ArcGIS format. In recent years, Jane Schafer-Kramer created an ArcGIS version of this grid. Jane developed, under Ralph Finch's guidance, an ArcGIS referenced grid by manually putting nodes at the closest location based on the PDF version of the grid. Again, the channel lengths from these would not match either CSDP or the original grid as it is an independent manual effort. Furthermore, there would be a mismatch to the location of the cross-section positions.

In 2012, Tom Heinzer was contracted to develop an ArcGIS-based extension to allow a user to develop cross-sections from DEM, which in turn is based on interpolations of depth sounding data. This again is a work in progress and cannot import the current cross-sectional profiles available in CSDP.

In 2017, CSDP grid data for the 2009 calibration was imported into ArcGIS along with the channel outlines and node locations. The channel outlines in ArcGIS were used to calculate lengths for the channels, and these were then compared to the current grid. There were many mismatches discovered, and these should be addressed in future efforts.

2009 Grid

The 2009 Grid is used for DSM2 v8.2. It is similar to the PDF grid map, but it includes some upper Sacramento River changes.

The node locations and the associated channel network lengths do have a match with the 2000 calibration files (spot checked). However, the 2009 CH2MHill mini calibration adjusted node positions, channel lengths, and cross-sections for channels 412-418. The changes made in these channels were incorporated into DSM2 and are included in DSM2 versions as recent as v8.2.0, which is the current release as of 10/2019. However, we did not get any CSDP or GIS data from CH2MHill. Node locations were reverse engineered using the mini calibration lengths, starting with the common node position from channel 412. The overall sum of the length (reach 412-418) was unchanged, and this assumption allows for a reasonable reverse engineering effort.

This reverse engineered effort is available on the shared drive as shapefiles \cnrastore-bdo\Delta_Mod\Share\maps\csdp_2009_calib_converted\CSDP_Channels_Adjusted_MiniCalib.shp (channels) and \cnrastore-bdo\Delta_Mod\Share\maps\csdp_2009_calib_converted\CSDP_Nodes_Adjusted_MiniCalib.shp. The Nodes shapefile is missing some files and cannot be loaded into ArcGIS. It was loaded into OpenJUMP and exported to \cnrastore-bdo\Delta_Mod\Share\maps\csdp_2009_calib_converted\CSDP_Nodes_Adjusted_MiniCalib_Recovered.shp. These files are also available in \nasbdo\Modeling_Data\DSM2_GIS_CSDP_gridmaps\GISGridmapV8.2.

These layers are the closest approximation to the grid used for DSM2 v8.2.

There is a large discrepancy in the channel length for channel 422 between cross channel and northern head of Georgiana slough. CSDP and ArcGIS calculations put it at 3300 feet, while in DSM2 input files it is 5300 feet. This is not an isolated incidence; there are many others as documented in this CSDP_vs_Channels_inp_Lengths.xlsx.

DSM2 v8.1 and v8.2 Grid

For version 8.1 and 8.2, use this grid for referencing DSM2 elements approximately. The channels and nodes layers are incomplete, not very accurate, and contain errors.

Shapefiles are available in \nasbdo\Modeling_Data\DSM2_GIS_CSDP_gridmaps\GISGridmapV8.2\

DSM2 v8.3 Grid

The 2019 grid is used for DSM2 v8.3, which is under development, and will be the result of the DSM2 GIS Reference Project.

Three shapefiles (located here: \nasbdo\Modeling_Data\DSM2_GIS_CSDP_gridmaps\GISGridmapV8.3) each have been created from the CSDP network (channel centerlines) and landmark (nodes) data for both the 2009 calibration (DSM2 V8.2) and the 2019 calibration (DSM2 V8.3). The shapefiles were created by exporting network and landmark data from the CSDP to WKT files and importing the results into QGIS, then saving to shapefiles. This is intended to be a first step toward creating a georeferenced grid map. Shapefiles are available in \nasbdo\Modeling_Data\DSM2_GIS_CSDP_gridmaps\GISGridmapV8.3\

  1. dsm2_channels_centerlines contains the channel centerlines as created in the CSDP. Many channels have endpoints that are not located at the node; this was done to improve the accuracy of the DSM2 channel volume. Also, many centerlines do not follow the actual channel centerline perfectly.
  2. dsm2_channels_straightlines contains straight lines connecting the two endpoints of each CSDP centerline.
  3. dsm2_nodes contains the CSDP landmark data. The node locations were previously not very accurate; they have now been corrected.
  4. dsm2_boundary_flow_nodes contains points placed at the locations of nodes where boundary flows are applied.
  5. dsm2_boundary_stage_node contains a point placed at the location of the node where the boundary stage is applied.
  6. dsm2_gates contains points placed at the approximate location of the channel centerline near each gate. In DSM2, gates are located at the ends of channels. The points in this layer are intended to represent the approximate location in DSM2, and not necessarily the physical location of the gate.

Future Directions

We need a georeferenced grid map. It should have the following features:

  1. Display nodes as circles with numbers inside.
  2. Display straightline channels with numbers, and an arrow indicating positive flow direction.
  3. Display channels derived from CSDP centerlines, with numbers, and an arrow indicating positive flow direction.
  4. Straightline channels and CSDP centerline channels should be different colors.
  5. Useful for printing on a plotter.
  6. Easy to modify when CSDP node locations or channels change.

  7. Good contrast with background, so we can easily determine connectivity and read all the numbers.

  8. Michael Mehrdadi is working on an ArcGIS grid map using the shapefiles for the 2019 grid.

  9. Hans Kim is working on a Google Earth grid map. This will likely be a useful training tool and may have other uses.
  10. The current version (as of 10/31/2019) of the grid map is found here: DSM2_Grid_191029.kml. It can be opened with Google Earth or imported into Google Map.
  11. Updates will be made as new shapefiles become available.

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