Online public discourse faces many threats such as human and bot networks spreading disinformation or harassment campaigns aimed at excluding certain voices. One such threat is the strategy of 'flooding the zone': intentionally pumping into the discourse information that is irrelevant to, or distracting from, an important issue. This technique is employed by both individual and state actors with seeming success. How and why that technique is successful, by contrast, is less well understood. In this paper we use agent-based modelling to help elucidate the disruptive impact of flooding the zone on communication itself. Specifically, we probe the ways in which flooding hampers the spread of relevant information and show consequences of this even for idealized, rational, actors.