The Initial Attack Assessment index (IAA) is a dynamic risk indicator that evaluates challenges faced by response teams during the first one to two hours after ignition. Initial Attack is the action taken by the first resources to arrive at a wildfire incident.
IAA is computed using automated and individual fire simulations with two indices: Fire Behavior Index (FBI) and Terrain Difficulty Index (TDI). The final IAA output is on a one to five scale; higher values indicate more active fire behavior, complex terrain, and greater likelihood of escaping initial attack.
IAA was designed by expert criteria and helps prepare resources for deployment. Its main advantage is ease of understanding for operational end-users.
Although IAA gives a quick approximation of the suppression difficulty of each fire, note that the index is not valid for longer fire durations than two hours (i.e., when the fire is not contained in the initial attack). This index is not recommended to estimate suppression difficulty in an Extended Attack Assessment (EAA).