# Assessment of Interventions in Fuel Management Zones Using Remote Sensing
## 1 Introduction  
Every year in Portugal thousands of hectares of forest are consumed by fires causing environmental, infrastructural, and personal damages [1]. With the purpose to minimize the damages caused by fires, the Portuguese government established Fuel Management Zones (FMZs), which are zones where the vegetation has to be treated, meaning the removal or partially removal of vegetation, to protect different types of infrastructures and to also work as strategic points for fighting fires [2, 3]. Since responsibility of the treatment of FMZs falls onto who owns a certain terrain, like like citizens, private entities, as well as counties, actively monitoring the treatments of FMZs is critical. The National Republican Guard is responsible for the monitoring of the FMZs. FMZs cover a large part of the Portuguese territory forming a three-level network: Primary Network, Secondary Network, and Tertiary Network. The primary network is defined at the district level, while secondary and tertiary networks are defined at the municipal and local levels. Furthermore, the interventions made in these zones are classified as follows: Fuel Reduction Zones (FRZs) and Fuel Interruption Zones (FIZs). FKZs are characterized by the removal of surface vegetation and the cutting of trees to create a separation between cups. FIZs consist of the total removal of all types of vegetation within the defined range [4]. The primary FMZ covers a large part of the Portuguese territory, dividing it into plots with a size between 500 ha and 10,000 ha. This network consists of 125 m wide strips. Beyond reducing the area traveled by forest fires, these strips are also an auxiliary element in the planning of firefighting, since this network is built in strategic areas. The secondary and tertiary FMZs are defined around roads, tracks, powerlines, railways, and settlements. These networks are part of the Municipal Plan for the Defense of Forests Against Fires. The strips created along roads, tracks, and railways are of the FIZ type. Strips around individual houses and settlements are also FIZ types with the addition that the canopy of trees must be more than 5 m apart from the dwellings. High and medium voltage electrical distribution lines and natural gas transmission lines are also part of these networks. Since FMZs can have huge extensions (thousands of hectares), it can be difficult for the authorities to monitor these zones and identify which ones require intervention. The existence of automatic or semi-automatic processes that allow the identification of FMZs that were treated, could help the monitoring process, speeding up the detection of zones in need of intervention, thus allowing timely maintenance and increasing the overall protection against forest fires. The use of machine- learning methods applied to remote sensing for large scale geographical analysis is common [5; 6; 7; 8]. The Institute for the Conservation of Nature and Forests (ICNF) maintains the geographical information about FMZs and makes this information publicly available. Combining this information with publicly available satellite imagery from satellites such as Sentinel-1 and Sentinel-2 that that capture images with resolutions up to 10 by 10 m, opens up the possibility of integrating new methods that use remote detection in the FMZs monitoring process. The FMZs must be treated every year so that during the fire season the vegetation inside is as reduced as possible so that these zones fulfill their purpose. The high extent of these zones and the fact that a large part of the FMZs intersects with private land can hinder the cleaning process and generate discontinuities in the treated areas of the FMZs. These factors make monitoring the treated zones or detecting zones in need of intervention a complex problem. Although forest fires are a serious problem, there has not been extensive research into the monitoring process of FMZs.