Decision Support Tools to Describe, Analyze and Interpret Forest Health and Fire Conditions in the Sacramento River Watershed

Healthy Forests

Forests play an important role in the health of a watershed. The Sacramento River is the largest river and watershed system in California. This 27,000-square mile basin drains the eastern slope of Mt. Shasta, the western slopes of the Cascades and the northern portion of the Sierra Nevada and provides 31% of the state’s total surface runoff. Much of that runoff comes in the form of snow and rain in the forests of the Sierra Nevadas. Healthy forests help trap water, reducing runoff and increasing infiltration to support in-stream flows and groundwater recharge. Forests of all types – coniferous, oak woodland, riparian, grassland – provide critical wildlife habitat and support local economies. Healthy forests are less likely to experience catastrophic wildfires and can be easier to suppress when they do burn.

 

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Decision Support Tools for Forest Health

The health of our watersheds is increasingly monitored and evaluated so that managers and stakeholders can make informed decisions about our natural resources.    Forest health is a topic of growing importance in the SRW due to ongoing drought conditions and the historic suppression of wildfire.  To make informed decisions about forest health and fire, 34 North extended the Sacramento River Watershed Program Data Platform to include tools and data to support fire research and landscape level assessments, restoration, planning, and prioritization.  The platform provides access to the state and local real time sensor networks, statewide monitoring data, maps, studies, reports, images, and GIS data from all major agencies including CalFire.  Users can explore and organize data spatially, create interactive maps, create and share projects, and use various catalogs and analytics to better visualize data collections or answer questions about watershed conditions. The project included adding hundreds of GIS layers, web mapping services, and web feature services that enhance the visual presentation of critical areas throughout the region.

Telling the Story of Forest Health

To tell the story about forest health in the Sacramento River Watershed, 34 North developed data stories using data from the decision support tool infrastructure created for managers.  The project includes data visualizations and stories that help communicate forest health conditions to the general public. Our team focused data products to include extensive spatial visualizations to emphasize important details like the changes in fire return intervals, insect and disease affected areas, fire threat assessments, tree mortality, vegetation types and more.

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Some of the data sets we discovered as part of the project included geodatabases that classified changes in fire return intervals based on detailed vegetation types in the National Forests of California. Based on historic fire data and known fire return intervals for specific vegetation types, the US Forest Service created a database for each National Forest that classified vegetation polygons into fire return intervals for pre-Euro American settlement (the 1800’s) and current (2015) conditions. Processing the layers for use and display on the OpenNRM platform was an exciting challenge and provided excellent spatial maps for public consumption.

For the geodatabases to be visually communicated as understandable information our team dedicated time to research key metadata and attributes of the database to allow for appropriate styling of the attributes. Geospatial information is most valuable when it is visualized in a clear, concise, comprehensible manner. The fire return interval geodatabases were essentially a detailed vegetation analysis with associated fire return intervals assigned to specific vegetation types. The databases contained attributes for both historic and current fire return intervals requiring the creation of two versions of each National Forest database. Using the open-source geographic information system, QGIS, each version of the database was processed into GIS layer format, styled categorically, and pushed through a simplification tool to allow for better web-based display. After processing in QGIS, the layers were uploaded to the Sacramento River Watershed OpenNRM Platform using a custom GeoServer database stack. Finally, the style categories developed in QGIS were translated through the GeoServer to create a suite of layers that communicate the extreme changes in fire return intervals of the vegetation of our forests.

The image below displays both a historic fire return interval and current fire return interval layer for the Tahoe National Forest. Each layer is categorized with the same color and time scale to easily visualize the shift in fire frequency that has occurred over the past century and a half. The right side of the map that is mostly shades of blue and yellow are current fire return intervals and indicate longer fire return intervals than the historic layer on the left side of the map. This data describes the change in frequency of fires due to human settlement and prolonged fire suppression. This information can help the public better understand the need for forest health treatments including prescribed burning, thinning, and new suppression techniques that allow wildfires to burn longer in safe areas.

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Historical and Current Fire Return Interval GIS layers for the Tahoe National Forest on the Sacramento River Watershed Program Data Portal