As per the question, the component of 'figures presented at the front of the billboard regarding the flood victims' would be suitable to the conviction of decisive movement propagated by Cartier-Bresson. These figures represented on the billboard most likely display Cartier's decisive moment.
In his book, Cartier gave a new dimension to his photojournalism and displayed different images in his books that highlighted the transient and voluntary events where the image gives a key idea about the entire event. He says such moments require 'knowledge' and 'intuition' to be captured precisely after observing closely.