Identifying object protection forest for natural hazards with the model Flow-py&#160;
Authors: D'Amboise Christopher , Plörer Matthias , Hormes Anne , Adams Marc , Kleemayr Karl , Teich Michaela 
Published: March 2021

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&lt;p&gt;We present&amp;#160;object protection forest&amp;#160;maps&amp;#160;for&amp;#160;rockfall,&amp;#160;shallow&amp;#160;landslides&amp;#160;and snow avalanches, which were&amp;#160;generated&amp;#160;within the Interreg Alpine Space project GreenRisk4ALPs&amp;#160;with the&amp;#160;runout model&amp;#160;Flow-py.&amp;#160;Six&amp;#160;Alpine&amp;#160;regions&amp;#160;with&amp;#160;varying&amp;#160;sizes from&amp;#160;45&amp;#160;km2&amp;#160;to&amp;#160;2250&amp;#160;km2,&amp;#160;and topographies,&amp;#160;from steep valleys of Val Ferret in&amp;#160;Italy&amp;#160;to the German Alpine&amp;#160;foothills&amp;#160;in Oberammergau,&amp;#160;were modeled.&amp;#160;&lt;/p&gt;
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&lt;p&gt;The term direct object protection forest is used for forests&amp;#160;that protect objects in developed areas against gravitational natural hazards. That is, a direct object protection forest can only be assigned, if an object is endangered and a direct link between the precise locations of the hazard process area and the object can be established.&amp;#160;The&amp;#160;two main&amp;#160;protective effects forests&amp;#160;can have&amp;#160;against&amp;#160;gravitational&amp;#160;natural hazards are&amp;#160;1)&amp;#160;to&amp;#160;reduce&amp;#160;the&amp;#160;release&amp;#160;probability,&amp;#160;or&amp;#160;2)&amp;#160;to&amp;#160;reduce&amp;#160;the magnitude of an event, the effectiveness of both is dependent on forest structure.&amp;#160;In addition, the degree to which the forest&amp;#160;reduces&amp;#160;the&amp;#160;energy&amp;#160;(magnitude)&amp;#160;of the hazard&amp;#160;also&amp;#160;depends&amp;#160;on&amp;#160;the&amp;#160;speed of the mass.&amp;#160;If the magnitude/speed of a hazard process is too high, the forest will be destroyed.&amp;#160;The location&amp;#160;of&amp;#160;a&amp;#160;forest&amp;#160;therefore determines its protective effect in two ways.&amp;#160;First,&amp;#160;high elevations&amp;#160;and steep&amp;#160;terrain (over 45&amp;#176;)&amp;#160;will produce&amp;#160;a&amp;#160;weaker&amp;#160;structure&amp;#160;and be less&amp;#160;effective against&amp;#160;gravitational natural hazards&amp;#160;compared to&amp;#160;lower&amp;#160;elevation gentle sloped terrain.&amp;#160;Second,&amp;#160;the energy of the hazard will be&amp;#160;lower&amp;#160;closer&amp;#160;to the hazard&amp;#8217;s release and runout&amp;#160;areas&amp;#160;than in the middle of the&amp;#160;process&amp;#160;path.&amp;#160;&lt;/p&gt;
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&lt;p&gt;Based on these relationships, we generated two types of&amp;#160;object protection forest maps:&amp;#160;&amp;#160;&lt;/p&gt;
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&lt;p&gt;(i) maps that highlight existing direct object protection forest&amp;#160;&lt;/p&gt;
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&lt;p&gt;(ii) maps that show where&amp;#160;direct object&amp;#160;protection forests have&amp;#160;or would have&amp;#160;the highest potential to either reduce release probability or&amp;#160;reduce the energy of the&amp;#160;hazard&amp;#160;&lt;/p&gt;
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&lt;p&gt;The&amp;#160;Flow-py&amp;#160;model&amp;#160;was used to model the&amp;#160;routing and stopping of the&amp;#160;three&amp;#160;hazards&amp;#160;and to establish the link between endangered objects and the hazard process&amp;#160;areas.&amp;#160;Input data&amp;#160;are&amp;#160;digital elevation models&amp;#160;(10 m resolution)&amp;#160;and&amp;#160;locations of release&amp;#160;areas&amp;#160;as well as a GIS layer&amp;#160;containing&amp;#160;locations&amp;#160;and types&amp;#160;of&amp;#160;objects, which is required for a custom plugin.&amp;#160;The&amp;#160;Back-calculation&amp;#160;plugin was used&amp;#160;with the Flow-py model&amp;#160;to identify&amp;#160;areas&amp;#160;on the terrain&amp;#160;(release areas, transit paths and deposition areas)&amp;#160;that are associated with endangered&amp;#160;infrastructure.&amp;#160;To obtain the first maps, the&amp;#160;model&amp;#160;outputs&amp;#160;were&amp;#160;overlaid with&amp;#160;digital&amp;#160;maps of existing forest areas to identify direct object protection forest.&amp;#160;The second map was produced by using the&amp;#160;same model&amp;#160;outputs&amp;#160;and digital terrain models&amp;#160;to&amp;#160;identify&amp;#160;areas&amp;#160;in the process paths&amp;#160;where the modelled hazard energy&amp;#160;was&amp;#160;low and effective protection forest can grow.&amp;#160;&lt;/p&gt;
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&lt;p&gt;The presented maps can&amp;#160;help to support decisions and&amp;#160;prioritize interventions&amp;#160;in&amp;#160;risk-based protection forest&amp;#160;and&amp;#160;ecosystem-based&amp;#160;integral&amp;#160;natural hazard risk management in the&amp;#160;Alpine Space.&amp;#160;&lt;/p&gt;
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&lt;p&gt;&amp;#160;&amp;#160;&lt;/p&gt;
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