Using Gis To Display Urban Watersheds In Google Earth

We present our methodology to generate a Google Earth-based interactive map of the creeks and watersheds of the urban San Francisco Bay area.

03 Jun 2015
Marco Ticci, Janet Sowers

Abstract

The Watching Our Watersheds (WOW) maps depict the present and historical surface water drainage, and include information icons that pop-up with an image or text with more information. Dense urbanization has resulted in the disappearance of many of the local creeks through the flatlands surrounding the bay. These creeks now flow in underground pipes, often surfacing to run through a park, then disappearing again. Municipalities and water agencies trying to reduce non-point-source pollution are faced with a public that cannot see, therefore does not understand, the interconnected nature of the drainage system or the extent of their neighborhood watersheds.
The creek and watershed data were created in ArcGIS through compilation of drainage data from the cities and counties, compilation of historical data, and digitization of visible features from aerial imagery. We present our workflow, from getting all the different layers ready in GIS, both spatially correct and complete with associated attributes, and symbolizing them in a matter that would be visually appealing and at the same time convey the appropriate information, to exporting them to KML format to replicate the compilation in Google Earth. The choice of using Google Earth to display our data is driven mostly by the fact that it is free to the public, it’s very user-friendly, and it also provides great base imagery, along with other layers such as roads, boundaries, etc.
As we were working on this project, we realized that there were some limitations in Google Earth that would need to be addressed through a series of geoprocessing tools and other steps before we could complete the conversion. These consisted in: creating a buffer for line features to address scale limitations and data accuracy; reducing the number of vertices for line and polygon features to limit the file size and improve the 3D rendering in Google Earth; using a raster to represent specific areas with very complex and detailed features; setting the symbology in GIS in a way that could be supported in Google Earth; truncating the number of decimals associated with the coordinate values to reduce the file size.
We’d like to share the lessons we’ve learned and all our tips and tricks to successfully migrate our GIS database to a complete, aesthetically pleasing, interactive map of creek and watershed data that can be used in Google Earth both by professionals and the general public to gather more information about this topic.

 

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