Montana’s Model Subdivision Regulations: A Statewide Strategy for Flood-Resilient Development

Background

Montana’s unique geography—spanning mountains, valleys, rivers, and plains—makes it vulnerable to flood hazards, including flash floods, snowmelt, ice jams, and dam failures. With a sparse population and minimal impervious surface, the state faces irregular but intense flooding events, such as the record-setting disaster in 2011, which caused over $60 million in damages and prompted a presidential disaster declaration.

Recognizing the recurring risk, Montana developed Model Subdivision Regulations and Model Floodplain Hazard Management Regulations to guide local governments. These models serve as planning tools for communities to adopt flood-resilient subdivision designs.

The Problem

Montana communities are vulnerable to diverse and unpredictable flood events due to climate variability and topography. Many subdivisions were historically sited near streams without adequate flood studies, exposing residents and infrastructure to serious risk. Local governments needed stronger tools and guidance to prevent unsafe development and improve flood preparedness statewide.

The Strategy

Montana’s response was twofold:

1. Model Subdivision Regulations:

   • Prohibit subdivision of land within known floodways or areas prone to flooding (Title 76, Chapter 5 of the Montana Code Annotated).

   • Require flood hazard evaluations for developments near streams lacking official floodway studies. These evaluations must be completed by licensed engineers following state guidelines.

   • Specify that development near a stream (within 2,000 feet horizontally and 20 feet vertically) must provide a detailed analysis if no mapped floodplain data exists.

     
     

2. Model Floodplain Hazard Management Regulations:

   • Require subdivisions to consider base flood elevations and boundary mapping during design.

   • Mandate flood-safe siting for structures, adequate surface water drainage, and secure utility placement.

   • Enforce local floodplain permit requirements before development in regulated flood hazard areas.

   
   

Together, these models help local governments mitigate risk, protect infrastructure, and ensure development practices are in line with state and federal floodplain management standards.

Lesson Learned

Montana’s model regulations demonstrate how a state-level approach can empower local governments to better plan for and mitigate flood risks. By requiring detailed hydrological assessments and setting higher design standards, communities can avoid placing homes in harm’s way. The 2011 flood event underscored the urgency of such measures.