Challenge

Geological Hazard Abatement Districts (GHADs) are charged with managing geological hazards within their district. Blackhawk GHAD and Canyon Lakes GHAD, located in the San Francisco Bay Area, each manage risk related to property damage from potential landslides, which is high given the hilly terrain and wet winters in the area. Over a 15 year period, the GHADs had received quarterly data, each with about 15,000 data points tracking water levels, angles of slopes that have been sliding, and homeowner reported cracks. Farallon Geographics was asked to analyze the large volume of data to identify potential at-risk properties and then present this information using a web-based interface that would enable the GHADs to proactively manage landslide risks. 

Solution

Farallon first migrated the 15 years of quarterly data, originally maintained in Microsoft Excel, to an Oracle Express database. This provided a free database solution with 4 GB storage - more than adequate for the GHAD datasets. Farallon then performed a statistical analysis on the data to determine which combinations of data correlated to risk factors and to flag those locations that warranted further analysis for potential landslides.

Farallon reviewed the options to display the data using a web-based interface. Traditional GIS tools such as ESRI can provide the functionality but are costly and are difficult to scale to handle large numbers of users. Google Earth was chosen because of its speed, scalability, intuitive and familiar user interface, and no cost. Farallon created business rules to determine critical geographical points in the database and then display these as markers on the Google Earth map interface. Incident locations that exceeded threshold levels for risk were indicated by different colored markers. A user could click on a marker to see the address, incident link and a historical chart of relevant water level information. Clicking the incident link opens a popup window with detailed information about that incident.

GHAD staff can now see critical information on a map and tie it into potential problem areas. This GIS Mashup provides an intuitive and powerful decision support system with low cost, high speed, and easy scalability.

Categories: Web Applications, Enterprise Mashups, Geodatabase Design

Selected screenshots from the project

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Incident locations that exceed threshold

Detailed information about an incident