Drainage systems.

Requires a unit to use data from the most recent: (1) Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps; and (2) National Oceanic and Atmospheric Administration Atlas; to calculate and regulate storm water runoff from a developed or undeveloped plat. Authorizes a unit to use data from the neighboring state in closest proximity to the developed or undeveloped plat under consideration. Requires a plan commission or plat committee to take action on a plat application, including meeting with any stakeholders with a financial interest in the application, not later than 30 days after receiving the application. Provides that if a plan commission or plat committee fails to make written findings and a decision granting or denying primary approval to a plat not later than 60 days after a public hearing, then the plat is considered to have received primary approval.