GEI’s Alex Gray to Speak at the Blue Marble User Conference on 9/29

GEI’s Alex Gray will be an active attendee at this year’s Blue Marble User Conference, which makes a stop in Portland Maine on Friday, September 29^th. The conference is a gathering of geospatial professionals representing a wide variety of industry sectors, government departments, and academic institutions who share a common interest in Blue Marble’s GIS and geodetic technology.

Alex’s presentation is on “Using Global Mapper to Develop Terrain Files for Hydraulic Analysis,” and is scheduled for Friday, September 29^th.

Session Overview:

GEI recently completed a two-dimensional hydraulic analysis for a hydropower client on the Ohio River. The client needed to fix a damaged portion of hydropower infrastructure and GEI was hired to design the infrastructure. There was concern about elevated velocities both during construction and post-construction (compared to existing conditions) by the hydropower owner, the contractor, the engineer, and agencies involved in river navigation and hydropower regulation. GEI needed to show the client, contractor, engineer, and regulators that velocities associated with the post-construction design and construction process were not significantly greater than the existing conditions. USACE’s HEC-RAS software was used to estimate the velocities around the powerhouse for a range of river flows and three different terrain conditions: Existing, during-construction and post-construction. The velocities for the “during-construction” and “post-construction” conditions were compared to the “existing conditions” to quantify velocities for engineers and the contractor and their equipment (.i.e. barges) and to verify velocity deltas were negligible.

GEI used Global Mapper to develop the three terrain files (Digital Elevation Models). The “existing conditions” terrain file consisted of a Digital Elevation Model (DEM) created using LiDAR ground points and bathymetric survey points. Other portions of the dam that were not present in either survey were created using georeferenced shapefiles and known elevations for those areas. The “during-construction” and “post-construction” conditions were modified versions of the “existing conditions” DEM. They contained georeferenced shapefiles from engineered drawings with known elevations and other portions of the DEMs were modified by editing the point cloud. This included eliminating portions of the dam and replacing with a one-dimensional dam structure inside the model and creating a ramp along the river bank that will be used for access for construction vehicles and equipment.

About Alex Gray:

Alex is an Adaptation Specialist / GIS Analyst out of GEI’s Portland, ME office with five years of experience in the industry. Prior to coming to GEI he was an essential member of the Catalysis Adaptation Partners team, using his GIS analytic skills to build models to assist municipalities and community organizations in understanding their vulnerabilities to potential storm surges and sea level rise. At GEI Alex has developed methods to quantify climate-related risks and calculate costs and benefits for various adaptation strategies. Alex also assists the Portland, ME office with hydrology and hydraulics modeling for hypothetical dam breaches and maps resulting inundation boundaries for emergency action plans and creates other visual aids for decision-making.