Graham Matthews

President, Principal 623-0520

Graham Matthews founded GMA, formerly Graham Matthews & Associates, in the 1990 and developed the company into a respected consulting firm providing hydrologic and geomorphic monitoring, stream restoration design and implementation oversight, and bathymetric surveying.

Graham has over 35 years experience in hydrology and fluvial geomorphology, and over 30 years of experience in the design and construction of stream and riparian restoration projects. He has worked on hydrologic/geomorphic issues and stream restoration designs in California, Oregon, Nevada, Washington, Nebraska, and Idaho. Recent project construction has included the Tracy and Mustang Reaches of the Truckee River for the Nature Conservancy, the Lorenz Gulch Project for the Trinity River restoration Program and the Wood River Project Phases 4-5. Past projects include the Angora Creek SEZ Restoration Project in South Lake Tahoe for the County of El Dorado DOT, the Williamson River Delta Restoration Project for the Nature Conservancy, the Clear Creek Channel Restoration Project Phase 3 for the Western Shasta RCD, the Agency Creek Dam Removal and Channel Restoration Project , the Crooked Creek Channel Restoration Project, the Wood River Channel and Wetland Restoration Project (Phases 1-3), and several project designs and over 2 miles of channel restoration projects construction on the Carmel River, CA. Most of these projects have included surveying, analysis, design development, specification development, permits, and construction management. Other recent projects include large bathymetric mapping projects on the Trinity, Russian, Green, and Clackamas Rivers.

Dave Edson


Dave is a licensed land surveyor with over 35 years experience in a wide range of survey practice, including: expertise in directing and performing all aspects of acquiring, processing, analyzing and compiling data to prepare maps, documents and deliverables for boundary surveys, topographic and bathymetric surveys, control and design surveys, subdivisions, records of survey, ALTA/ACSM surveys, and lot line adjustments/easement acquisitions.  Experience also involves the preparation of land use proposals, along with the preliminary and final subdivision plat submittals, field work including; section control, field record research, the development of supportive data reports, and extensive construction staking. Numerous land development projects from two lot minor subdivision plats, to the major subdivision requirements have been completed.  Recent work with GMA has focused on control surveys used for various bathymetric survey projects as well as the surveys themselves.  Dave provides oversight and certification of all GMA survey products.

Geoff Hales


Cort Pryor

Survey Manager, Project 834-1906

Cort is responsible for planning, conducting, and processing land, hydrographic, and aerial surveys related to stream restoration, geomorphic monitoring, flow study, and fisheries habitat projects. He works under the direct supervision of GMA’s licensed surveyor in order to ensure that surveys are planned and carried out in an efficient manner and that they meet the accuracy requirements of the project. Cort also designs surface water (quantity and quality) and sediment transport monitoring programs.  He performs a wide range of data analysis in the hydrologic environment including but not limited to flood frequency analysis, flow duration, trend analysis, and review of streamflow and sediment transport records. Cort is and Engineer in Training (EIT) in the state of California and is certified by the USGS in Sediment Data Collection Techniques (SW1091 TC), Sediment Records Computation & Interpretation (SW2096), and Streamflow Records Computation using Hydroacoustic Current Meters and Index Velocity Methods.

Tom Grey 834-0191

Thomas Grey has over 16 years of experience in hydrologic related fields and surveying. He has extensive experience in fish passage work, primarily with using the FishXing software model and has collected field data by Total Station and Auto Level surveying for culvert removal and replacement, tide gate removal and for weir installations. He has been involved with developing work plans using GIS and AutoCAD. Thomas was responsible for management of the hydrologic WISKI database used to analyze streamflow and sediment transport data.  Responsibilities included rating curve development, streamflow records computations, collecting streamflow measurements by wading, bridge, and boat methods, collection of storm related streamflow data, sediment transport data and the installation and operation of streamflow gages.

Dan Sheldon

Survey 331-6518

Dan Sheldon has a BA in mathematics from the University of California at Santa Cruz and a Civil Engineering Technology certificate from Santa Rosa Junior College. He is currently a member of the California Land Surveyors Association and is working towards attaining his LSIT. Dan primarily collects survey data for GMA, using both conventional survey methods and multi-beam and single beam sonar techniques. He also provides expertise toward data processing and integration software used to create many of the survey products at GMA.