Innovations in Stormwater Inventory Data Collection City of Greensboro, North Carolina

The City of Greensboro is currently developing a modern, dynamic, GIS-based stormwater management system. The first part of the system consists of a complete inventory of the stormwater infrastructure and conveyance system inventory for the entire City. The stormwater and conveyance system inventory has been completed for portions of two principal watersheds in the City (North and South Buffalo Creek watersheds). The current phase (Phase III) of the project includes the remaining areas in the City and is organized and will be completed on a watershed-by-watershed basis. The City of Greensboro is being assisted in the inventory by Dewberry & Davis, Inc. and Concord Engineering & Surveying. Dewberry & Davis is serving as the prime consultant. Using a combination of Global Positioning Systems (G.P.S.) survey and conventional surveys, storm drain structures are surveyed to determine the 3-D coordinates of drainage point features including: curb, grate, and yard inlets; junction boxes and manholes; pipe inlets, outfalls, and energy dissipaters; swales, channel and creek sections; bridges and culverts; lakes and stormwater management facilities (ponds). Information (attributes) is collected for each storm drain structure such as pipe diameters, pipe elevations, pipe slopes, dimensions, materials, structure and surrounding conditions, tie-in's, stilling basin data, flood evidence, damage potential, scour, and connectivity, type of discharge, flow, color, odor and other factors. Numerous measurements are made of headwalls, bridges (including abutments and piers), culverts (including barrels), lakes and ponds (including spillways, risers, etc.). Photos are taken of all storm drainage structures using digital cameras. Cross sections are also being surveyed along major creeks for use in development of computer simulation models (HEC-RAS) for predicting flood hazard areas and water quality conditions. A primary key to the success of Greensboro inventory program has been technology. This technology is currently being used by field crews to ensure the quality and accuracy of the data collected. Survey crews are using Real Time Kinematic (RTK) G.P.S. Receivers with accuracies of +/– 5 cm for both horizontal and vertical coordinates. Feature attribute crews are using state-of-the-art, Pentium-based pen computers and custom developed software to allow for the direct creation and editing of GIS shapefiles in the field where the data is collected. To facilitate the accurate, efficient, and safe (without structure entry) measurement of structure depths and pipe elevations, Dewberry & Davis has developed a one of a kind laser measurement device that measures the vertical difference in elevation from the manhole rim to the pipe inverts. The project also involves a rigorous quality assurance and quality control program to ensure data collection and GIS integration standards.