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Track: Water Distribution, Wastewater, Sewer
Michael McGuiness
County of Snohomish
2930 Wetmore Avenue
Surface Water Management Division
Everett, WA 98208
Telephone: 206-388-3464
Fax: 206-388-6455
Phil Berlin
Use of GPS, GIS. Laser Technologies in Inventory and Modeling of Surface Water Drainage System
Defining Issue: An inventory of a surface water drainage facility can be a labor intensive and time-consuming task. In addition, modeling of the system requires accurate elevation data on catch basin grates and pipe inverts. GPS/GIS Solution: Faced with hiring freezes and limited staff, Surface Water Management (SWM) decided to use the most current technology to increase existing staff efficiency in inventory of the constructed drainage system. Trimble Real Time Kinematic (RTK) Survey Grade GPS was used to collect catch basin position and attribute data in the field. Horizontal and vertical accuracy of the RTK GPS is plus/minus 1 cm. GeoLaser technology was used to collect position and attribute data in areas where GPS satellite lock was unattainable. Horizontal and vertical accuracy of the GeoLaser is plus/minus 10 cm. Field pen-based computers and pen-based software technology were used to provide connectivity between GPS point data and to enter pipe attribute data in the field. All field data were
imported in ArcView Version 3.0. Shapefiles were created to allow the field crew to view the previous day's work in the field. ArcView Version 3.0 was used to export drainage system data to a hydraulic model for analysis of the constructed drainage network. Methodology: SWM is now beginning to realize the many applications and benefits of having a highly accurate and detailed constructed drainage network on GIS. - Modeling capabilities allow SWM engineers to analyze a catchment area and identify drainage network problems with the existing development or from new development. - GIS allows SWM water quality specialists to track pollutants through a drainage system and address water quality problems more efficiently. - Enhanced efficiency in SWM's ability to research and respond to public inquiries regarding localized flooding and drainage problems. - Enhanced maintenance of surface water facilities and project planning for replacement of aging pipes and other structures. Software: SWM used the Trimble
GPSurvey software for database development of catch basin and pipe and ditch nodes and for export to ArcView Version 3.0. GeoLaser software was used to collect attribute data on catch basins where GPS lock was unattainable. PenMetrics Field Notes and Field Form software were used to add pipes (snap connectivity) between catch basins and other nodes in the field. Attribute data on pipes, ditches, and swales were added using field and line data from GeoLaser and Field Notes. Shapefiles were created for each day of work. At the end of each week, shape files were combined. Esri's ArcInfo Version 7.0.3 was used to convert the shapefiles to coverages and append the coverages into a master catch basin, pipe, ditch, and swale coverage. ArcView Version 3.0 was used to export all drainage system data, including x, y, and z coordinates and all attribute data to a dbf format of import into TerraModel. TerraModel was used to perform hydraulic analysis of the inventories constructed drainage system to identify
capacity and other problems within the system.
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