Statewide Fire Map 2 Production – Guidelines and Recommendations from the Independent Review Team (IRT)
September 25, 2017
The purpose of Fire Map 2 is to designate areas where there is an elevated hazard of utility-associated wildfires to occur and spread rapidly, and where communities face an elevated risk of damage or harm from utility-associated wildfires. The intent of Fire Map 2 is to delineate the boundaries of high fire-threat districts where stricter fire safety regulations might apply. To create Fire Map 2, an inclusive process was used, where entities potentially affected by California Public Utilities Commission regulations have been provided an opportunity to review and submit input on an interim map (Shape B Map) that represents potential wildfire threats across the state of California. Prior to the initiation of map change proposal submissions, the Peer Development Panel (PDP) and Independent Review Team (IRT) developed a risk assessment rubric/diagram (Figure 1) to guide Territory Lead’s and PDP’s development of map change proposals, as well as informing the IRT review of map change submissions.
Figure 1. Shape B utility fire threat evaluation rubric.
As a result of this process, about 130 map change proposals, representing approximately 1,400 polygons, were submitted to the Independent Review Team (IRT) for expert review and consideration for approval. Submitted map change proposals from Territory Lead and PDP included recommendations for individual service territories to either:
- Retain areas of elevated or extreme fire threat (i.e., no changes to Shape B)
- Remove land area from Shape B and reclassify as Tier 1.
- Include additional areas into Shape B as Tier 2, or Tier 3 areas.
- Elevate existing areas of Shape B as Tier 3.
Through the IRT review, each polygon was evaluated using a variety different sources of data, and assigned one of three general approval ratings, including 1) “Approved” – the polygon and associated Tier classification change was approved by the IRT for incorporation into Fire Map 2, 2) “Denied” – the polygon and associated Tier classification was rejected and thus should not be incorporated into Fire Map2, and 3) “Denied, Pending Revision” – the polygon and associated Tier classification should not be incorporated into Fire Map 2 until recommended revisions are approved by the IRT. In a few instances, an “Approval (with recommended changes)” determination was made, which can be interpreted to mean that the polygon, “as is,” is approved by the IRT, however additional guidance is suggested to Territory Lead to modify the polygon in order to improve map fidelity.
The IRT’s review of Territory Lead and PDP map change proposals resulted in several areas that warrant additional guidance to the PDP for developing the final statewide Fire Map 2. The following describes some of the issues encountered during IRT review, and offers solutions for rectifying them through the development of the final statewide fire threat map.
Polygon Line Work – Clean-up
Due to the varying levels of GIS expertise, and the tight timeline to get map change proposal submitted, the quality of polygon varied considerably across Territory Lead/PDP submissions. In many instance, polygon linework roughly traces the boundaries of Shape B to generally illustrate the where the change is proposed, rather than the actual area of change. Imprecise polygon work resulted in many polygons being classified by the IRT as “denied, pending revision.” Thus, the IRT recommends that:
- Polylines should conform to landform/landcover and topography, and breaks in fuel.
- When polylines occur between burnable open spaces and development, polygons a that interface should be set back into the development about 25 meters, as the interfacing development is considered burnable (unless there is sufficient defensible space surrounding development.
- Confirm that all Tier 1 requests are in fact non-burnable landscape features, or otherwise there is sufficient firefighting access and capacity to reduce risk to an acceptable/moderate level.
- Match/align polygon boundaries to adjacent district boundaries Tier designations.
- For topological errors (i.e., slivers and overlaps), match common boundaries to best reflect transition breakpoints between different Tiers, and create mutual typological polyline. Use standard GIS operations to fill small holes and delete splints caused by the mapping processes described above. The IRT is available to advise on this process if requested.
- In situations where Shape B lacks coverage (i.e., has holes) in burnable areas, and it makes more sense from an implementation perspective, the IRT approves of the filling of such hole to create a seamless coverage (within the context of Tier 2 or Tier 3 zones).
Denied, Pending Revision Polygons
If there are no IRT-approved revisions to identified “Denied, Pending Revision” polygons submitted to the ticketing system, then IRT considers those polygons as “Denied”, and thus such changes should not be included in the final map.
Which Polygon is Principal?
In situation where two or more polygons overlap, the polygon with the highest Tier trumps lower tiered polygons (i.e., Tier 3 takes priority over Tier 2, and Tier 2 takes priority over Tier 1).
The large majority of submissions characterized stakeholder engagement, however, few polygons submitted reflected actual stakeholder input. If possible, the IRT recommends additional outreach to ensure collaboration and agreement with proposed Tier delineations, prior to submission of the statewide fire threat map.
Tier 3 Polygon Delineation
The IRT is using the Integrated Utility Threat Index (iUTI) as a guide for identifying areas of possible Tier 3 status. Like the Fire Map 1 products, the iUTI is a coarse (2-km) raster built on broad-scale inputs; it is not meant to be used for drawing exact polygon boundaries, but instead for finding areas of California with similar values of integrated utility wildfire threat. By “integrated”, we mean the combination of both the likelihood of an escaped utility-associated wildfire and its harm/impacts to people and property if one should occur.
As a rough guide, we suggest that areas with iUTI values below the 85th percentile are weaker candidates for Tier 3 status. However, the TL and PDP may use local knowledge of fuel, weather, terrain, and residential and commercial development vulnerability to request Tier 3 status even though iUTI values are below the 85th percentile. Areas between the 85th and 95th percentiles are strong candidates for Tier 3 status. But, again, local knowledge should be used by the TLs and PDP to draw specific polygon boundaries. Where iUTI values are above the 95th percentile, the IRT is expecting Tier 3 status, unless there is strong evidence suggesting otherwise.
Please refer to specific IRT Reviews for service territory-specific guidance.