T.E.E.G.S. is committed to providing the highest quality GIS services to assist cities in ensuring that municipal services such as transportation systems and emergency services are able to function in a way that best serves the community and its citizens.
The record drought of 2011 severely weakened the structural integrity of an unknown number of trees in and around the city of Austin. Structurally weekend trees pose a potential and unnecessary hazard to both emergency and municipal response services. The tree hazard can be managed by appropriately maintaining the cityís trees near roadways.
The Urban Forestry Program (UFP), as part of the City of Austin Parks and Recreation Department, is responsible for the upkeep and maintenance of approximately 300,000 trees along roadways and city owned property in the City of Austin. The UFP and the City of Austin Parks and Recreation Department wish to be proactive in the identification and subsequent removal of potential tree hazards before they become a safety and insurance liability on the city roadways. Identifying the street segments with the greatest potential for tree hazards will help optimize the cityís tree removal services and clear potential hazards before they become a hindrance for emergency and municipal service vehicles.
Our Geographic Information Systems (GIS) consortium group, Transportation, Emergency, and Environmental GIS Services (T.E.E.G.S.) can help the UFP accomplish the task of tree hazard risk mediation through our expertise in GIS. Using a GIS, we will identify street segments with the greatest potential risk and correlate those locations with the highest priority routes for emergency services in order to optimize proactive preventative maintenance and reactive clearing.
We started with the identification of Origin points (Fire, Police, and EMS stations) and Destinations points (Schools, Hospitals & the centroids for the 150 most populous census blocks in the City of Austin). We then routed from each origin to each destination and compiled statistics on the number of times each road segment was used. We also identified percent tree canopy cover for each road segment by calculating the area of the street overhung by tree canopy & dividing it by the total area of the road segment. We then multiplied the percent tree canopy cover by the frequency for each road segment to identify the most critical road segments for pro-active tree maintenance.
The most difficult part of this project was creating a model that would run a point to point route analysis. Though this could be done manually, the number of origin and destination points used required around 20,000 routes to be created and would be extremely time intensive. The model required a creative application of knowledge in order to get around this problem.
We also had difficulties finding our points for origins and destinations. EMS, Fire, and Police Stations and school were all collected through Google Maps, which affects the accuracy of the points as well as being time consuming. We were unable to find a comprehensive list for the origin points, so there is no guarantee that all stations were included in our analysis.
Also, though it did not affect our process, our outdated data for both streets and tree shade affected our results. Because the tree shade and street polygons were last updated in 2006, our percent canopy cover is accurate and only to that date. Our road network comes from 2010, so it is more current, but when combined with the 2006 tree data, can only be considered accurate as of 2006, seven years previously.
After completing our analysis on Emergency Service response our group was returned with very interesting and to a certain degree somewhat expected results. Our Relative Ranking system that combined route frequency and canopy cover returned very clustered results; this clustering is due to the fact that only 10 percent of our analyzed road segments returned a score. These highly ranked road segments were strongly concentrated in 3 areas. These areas include The Shoal Creek area between 24th street and Enfield, the Barton Springs and South 1st area near Auditorium shores, and Cesar Chavez from Congress to Trinity.
The Shoal Creek area contains our highest ranked road segments as well as the densest concentration of high ranking road segments in the city. This area is strongly centered around Windsor, which returned our 1st, 2nd and 5th ranked road segments. Windsor is a major thoroughfare for traffic from Mopac as well as the nearby neighborhoods of Pemperton and Clarksville. As could be expected this major greenway through Austin presents a large amount of Canopy Cover that the Emergency Service personnel must travel through; this presents a large potential for E.S. personnel to be disrupted by downed limbs or entire trees when responding to minor or major emergencies in Austin.
The Barton Springs and South First area is centered near Auditorium Shores and the Long Center. Travelling East on Barton Springs from Lamar Boulevard travelers and E.S. personnel are confronted with a very dense canopy cover that could present potential problems during a severe weather event. These roads are important Arterial Streets for the nearby neighborhoods of Barton Hills, South First, and Travis Heights as well as area parks like Zilker Park and Auditorium that often times host major festivals and events. Because of the key role Barton Springs and South First Street serve in Austinís transportation system, both for civilian and municipal purposes; it is vitally important that the City of Austin Urban Forestry Program prioritize their efforts here by including this area as one of their top considerations for proactive tree maintenance.
The Downtown area of Austin, located on Cesar Chavez between Congress and Trinity, is our third area of interest we wish to alert the City of Austin Urban Forestry Program to. This area, like the Shoal Creek and Barton Springs area previously noted, is an extremely vital commuting corridor in town. This section of Cesar Chavez experiences considerable traffic from the two highways in town, Mopac and IH-35, as well as south and central Austin traffic from South First and Congress. Because of these factors, in addition to the high level of Emergency Service Personnel traffic, this area is an extremely important corridor for the City of Austin Urban Forestry Program to keep clear in order to ensure Austinís Street Network operates appropriately.
As we have pointed out, our results returned very strong clustering in the areas of Shoal Creek, Barton Springs/South First, and Downtown near Cesar Chavez and Congress. These areas are extremely important for the City of Austin Urban Forestry Program to prioritize for their proactive tree maintenance program, but in addition to these areas there are in fact other areas around town in need of proactive tree maintenance to adequately ensure a fluid response from Austinís Emergency Service Personnel.