A Live Fuel Moisture Content Product from Landsat TM Satellite Time Series for Implementation in Fire Behavior Models

Mariano García,Adrián Cardil,M Pilar Martín,Javier Salas,Lara Vilar,Susan Ustin,Marta Yebra,David Riaño,John Gajardo,Joaquín Ramirez,Santiago Monedero

doi:10.3390/rs12111714

Abstract

Live Fuel Moisture Content (LFMC) contributes to fire danger and behavior, as it affects fire ignition and propagation. This paper presents a two layered Landsat LFMC product based on topographically corrected relative Spectral Indices (SI) over a 2000–2011 time series, which can be integrated into fire behavior simulation models. Nine chaparral sampling sites across three Landsat-5 Thematic Mapper (TM) scenes were used to validate the product over the Western USA. The relations between field-measured LFMC and Landsat-derived SIs were strong for each individual site but worsened when pooled together. The Enhanced Vegetation Index (EVI) presented the strongest correlations (r) and the least Root Mean Square Error (RMSE), followed by the Normalized Difference Infrared Index (NDII), Normalized Difference Vegetation Index (NDVI) and Visible Atmospherically Resistant Index (VARI). The relations between LFMC and the SIs for all sites improved after using their relative values and relative LFMC, increasing r from 0.44 up to 0.69 for relative EVI (relEVI), the best predictive variable. This relEVI served to estimate the herbaceous and woody LFMC based on minimum and maximum seasonal LFMC values. The understory herbaceous LFMC on the woody pixels was extrapolated from the surrounding pixels where the herbaceous vegetation is the top layer. Running simulations on the Wildfire Analyst (WFA) fire behavior model demonstrated that this LFMC product alone impacts significantly the fire spatial distribution in terms of burned probability, with average burned area differences over 21% after 8 h burning since ignition, compared to commonly carried out simulations based on constant values for each fuel model. The method could be applied to Landsat-7 and -8 and Sentinel-2A and -2B after proper sensor inter-calibration and topographic correction.

Highlights

Fire disturbances play a key role in vegetation succession, as well as in the ecosystem’s structure and function [1]
This paper presents a two layered Landsat Live Fuel Moisture Content (LFMC) product based on topographically corrected relative Spectral Indices (SI) over a 2000–2011 time series, which can be integrated into fire behavior simulation models
Running simulations on the Wildfire Analyst (WFA) fire behavior model demonstrated that this LFMC product alone impacts significantly the fire spatial distribution in terms of burned probability, with average burned area differences over 21% after 8 h burning since ignition, compared to commonly carried out simulations based on constant values for each fuel model

Summary

Introduction

Fire disturbances play a key role in vegetation succession, as well as in the ecosystem’s structure and function [1]. Live and dead biomass constitutes the fuel that burns during a fire, and the fuel properties describe their state or moisture content, as well as their spatial distribution and impact on fire spread, intensity and severity [2]. Among these properties, fire ignition and propagation depend on Live Fuel Moisture Content (LFMC) [3,4,5,6]. LFMC is defined as the amount of water in the fuel over its dry weight times 100. The NFDRS considers the woody LFMC, measuring the moisture of the foliage and of small twigs that are < 0.6 cm [9]

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