Infrastructure is the combined facilities and structures that a society needs for its economy to function. It includes bridges, roads, telecommunications systems, water and sewage systems and electrical grids. Airports, tunnels, hospitals, lighthouses, public schools, parks and other public spaces also fall under the umbrella of infrastructure. The degree to which each is developed tells a lot about that society.
A primitive society might have dirt roads and wooden dams while a technologically advanced community would employ systems that perhaps have yet to be developed.
When creating the setting for your story, these elements might not play a major role, but they could. Imagine if an earthquake breaks the walls of a dam and water pours down river, flooding cities in its wake. Perhaps the local hospital is so overrun with accident victims that additional cases have to be transported to other communities.
Your task is to create a story in which something happens that threatens an element of the infrastructure. Begin by settling on the one event that you feel the most comfortable writing about. Place your characters in the scene, taking into consideration how the event will affect each and how they will react, realizing that people behave differently when threatened.
You can start with the disaster right from the beginning, or establish the “normal” world so that readers understand what life was like before things went wrong. Dialogue and narrative are both important. Narrative puts readers into the heart of the action while dialogue exposes the fears, the concerns, the reactions of characters in the story.
Have fun with this one.