CWPP Data (Online Map Viewer)
Disclaimer: The data displayed on the CWPP online map is for imformational use only. FIRESafe MARIN asks that viewers be cautious when interpreting the results - non fire professionals should seek advice from wildfire experts before drawing conclusions or interpreting data. For example, in many views, green is used to indicate lower flame lengths and rate of spread. This does not indicate a safety zone or area free from fire risk. Wildfire science is complex, and the modeled flame lengths, rate of spread, and composite mapping are not necessarily indicators of risk to infrastructure or populations.
For additional information see the CWPP document.
About the Data
To improve upon the currently available state-level fire hazard assessment information, an independent hazard, asset, risk assessment was performed to help identify and prioritize areas within the county that are potentially at a high threat from wildfire based on more recent fuels data, advanced modeling techniques, and local input. The assessment was performed by modeling potential fire behavior and the probability or likelihood that an area will burn given an ignition. Next, the fire modeling output was combined with areas of concern and assets at risk. Composite maps were generated indicating relative potential fire hazards throughout the county.
Additionally, fire behavior modeling was conducted under two fire weather scenarios. Two fire weather scenarios were chosen to represent annual wildfire conditions for an average fire season and a fire season under extreme fire conditions. The average fire season scenario was created by summarizing the weather and fuel moisture parameters from April through October (a typical fire season), and was used to represent the fire weather conditions during a typical summer day in Marin County. The extreme fire conditions scenario was created using the 97th percentile weather data from July through October, and represents the hottest and driest time periods during the summer months when fire behavior would be the most intense and difficult to control.
The information below describes each map layer within this application and explains how it’s used in the risk assessment process.
Marin Fuel Model 5m.tif: As part of the development of the CWPP, an updated, high-resolution (5 x 5 meter) gridded vegetation map was developed using a combination of vegetation data provided by local land management agencies and recently obtained LiDAR measurements (see Section 2.2 and Appendix A for the CWPP). The 5 x 5 meter data were used as input to FlamMap for modeling potential fire behavior.
2010 Census Block Population (people / square mile): Population density data for Marin County were acquired from the U.S. Census Bureau. The data were mapped and used in the hazard, value, risk assessment to identify populated areas, which represent areas with high structure density. These data were used as a surrogate for representing areas of high asset value that are important from a fire protection perspective.
Average Fire Season – Flame Length (feet) / Extreme Fire Conditions - Flame Length (feet): The FlamMap fire behavior model was used to model flame length under each fire weather scenario. Flame length is commonly used as a gauge of fire potential because it provides an indicator of possible fire behavior from a suppression perspective. Section 4.2.5 of the CWPP provides additional information on the flame length.
Average Fire Season - Rate of Spread (feet/minute) / Extreme Fire Conditions - Rate of Spread (feet/minute): Rate of spread is an indicator of how rapidly a fire might spread, and is defined as the rate of forward spread of the fire head expressed in feet per minute. FlamMap runs were performed for the two weather scenarios using the custom fuel model data developed for Marin County and topographical data (slope, aspect, and elevation).
Average Fire Season- Composite Map / Extreme Fire Conditions - Composite Map: The composite maps from the hazard, value, risk assessment were composed using a suitability modeling approach. Suitability modeling is a GIS-based method used for identifying areas based on specific criteria. For this work, suitability modeling was used to identify areas of high fire hazard (or concern) based on fire behavior potentials, population density, and proximity to areas of concern. The Environmental Systems Research Institute (ESRI) ArcGIS software, Spatial Analyst, was used for this analysis. Spatial Analyst is a raster- or grid-based software package that provides a platform for developing and manipulating gridded data. Spatial Analyst can be used to develop suitability models that produce maps highlighting “suitable” geographic areas based on defined model criteria and weighting schemes.
Population density, flame length, and rate of spread maps (Described above) were merged and processed to identify areas that have very high population density, flame lengths, and rate of spread. These data layers show the composite maps for each fire weather scenario; red and orange show areas of very high to high population density, flame length, and rate of spread. These are areas of high asset value where fire behavior is likely to be extreme.
Average Fire Season- - Areas of Concern Relative Ranking / Extreme Fire Conditions - Areas of Concern Relative Ranking: As part of the CWPP process, fire departments, land management agencies, and other stakeholders were asked to identify and provide information about the areas they are most concerned about within their jurisdictions. To help prioritize areas of the county where fuel reduction and hazard mitigation efforts might be focused, composite maps (described above) were overlaid with the areas of concern boundaries, and GIS processing methods were used to calculate spatial statistics within these areas of concern. This information was used to rank the areas of concern. The red areas in indicate the top 33% of the areas of concern, where population density, flame length, and rate of spread could all be potentially very high. The orange areas indicate the middle 33% (high) and the green indicate the lower 33% (moderate).
Fire Service Area: Boundary file for each Marin County fire service area. This data layers was included to allow users to click on and zoom to a desired fire service area