Dear Raktim,

The following text was taken from a report entitled "Bathymetric Survey

of the Guadalupe River December 2010 Survey " published by The Texas Water Development Board which demonstrate a commonly used and economical method for bathymetric survey of a river channel:

TWDB bathymetric data collection

TWDB collected bathymetric data on the Guadalupe River on December 22 and 23,

2010. The water surface elevation of Canyon Lake during that time ranged between 907.87 feet and 907.84 feet above mean sea level (NGVD29). TWDB used a Specialty Devices, Inc., single-beam, multi-frequency, (200 kHz, 50 kHz, and 24 kHz) sub-bottom profiling depth sounder integrated with differential global positioning system (DGPS) equipment, but only the 200 kHz returns representing the current bottom surface were processed for this study. Data collection occurred while navigating along pre-planned range lines oriented perpendicular to the assumed location of the original river channels and spaced approximately 250 feet apart. Many of the survey lines were those originally surveyed by TWDB during the 2000 volumetric survey of Canyon Lake (TWDB, 2001). The depth sounder was calibrated daily using a velocity profiler to measure the speed of sound in the water column and a weighted tape or stadia rod for depth reading verification. During the 2010 survey, team members collected nearly 27,300 data points over cross-sections totaling approximately 28 miles in length. Figure 2 illustrates locations of data collection during the 2010 TWDB survey. 

Data processing

Model boundary

The river boundary of the reach surveyed was digitized from digital orthophoto

quarter-quadrangle images (DOQQs), obtained from the Texas Natural Resources

Information System (TNRIS), using Environmental Systems Research Institute’s (ESRI) ArcGIS 9.3.1 software (NAIP, 2006, TNRIS, 2009). The DOQQs that cover the study section of the Guadalupe River are Fischer SW and Fischer SE. The DOQQs were photographed on May 2, 2010, while the water surface elevation measured 909.89 feet above mean sea level. The 2010 DOQQs have a resolution of 1-meter. The river’s boundary was digitized from the land water interface visible in the photos and assigned the elevation 909.89 feet.

Triangulated Irregular Network model

Following completion of data collection, the raw data files collected by TWDB

were edited using the software DepthPic to remove data anomalies. DepthPic is used to display, interpret, and edit the multi-frequency data and to manually identify the riverbottom surface. The water surface elevations at the times of each sounding were used to convert sounding depths to corresponding river-bottom elevations. For processing outside of DepthPic, the sounding coordinates (X,Y,Z) were exported. Using the self-similar interpolation technique (described below), TWDB created additional mass points files of interpolated bathymetric elevation data located between surveyed cross sections. The points file resulting from data interpolation was used in conjunction with the sounding and boundary files to create a Triangulated Irregular Network (TIN) model with the 3D Analyst Extension of ArcGIS. The 3D Analyst algorithm uses Delaunay’s criteria for triangulation

to create a grid composed of triangles from non-uniformly spaced points, including the boundary vertices (ESRI, 1995). The TIN model was then converted to a raster representation using a cell size of 1 foot by 1 foot. The bathymetric contours of the river were extracted from this raster and presented in 5 feet intervals in the attached contour map.

For more details on this method, please see the publication contained in the following link:

https://www.twdb.texas.gov/hydro_survey/GuadalupeRiver/2010-12/GuadalupeRiver2010_FinalReport.pdf

Another important publication which may be helpful is the U.S. Geological Survey contained in the following link:

http://pubs.usgs.gov/sim/3198/pdf/Ruby-SIM_032612web.pdf

Hoping this will be helpful,

Rafik

Thank you very much Rafik