Understanding Floodplain Determination in Southern Oregon

Floodplain determination is a crucial aspect of land use planning and development, as it helps communities understand their flood risk and make informed decisions about reducing or managing that risk. This article provides an overview of how floodplain determination works in Jackson County, Oregon. 

How are Floodplains Determined?

Floodplains are determined using Flood Insurance Rate Maps (FIRMs) developed by the Federal Emergency Management Agency (FEMA) in collaboration with local communities. In Jackson County, FEMA’s Flood Insurance Study (FIS) provides the basis for determining if a property is within the Special Flood Hazard Area (SFHA) and what development regulations apply. 

Floodplains are areas of land that are prone to flooding. In general, the criteria that make an area of land a floodplain include:

1. Proximity to a body of water: Floodplains are typically located near rivers, streams, lakes, or other bodies of water prone to flooding.
2. Low elevation: Floodplains are often located in low-lying areas where water can accumulate during heavy rainfall or snowmelt.
3. Soil type: The soil type in a floodplain can affect how quickly water is absorbed and how long it remains on the surface. Soils that are poorly drained or have a high clay content are more likely to contribute to flooding.
4. Topography: The shape of the land can also contribute to flooding. Areas with steep slopes or narrow valleys can channel water quickly and increase the risk of flooding.
5. Historical flooding: Areas that have experienced flooding in the past are more likely to be designated as floodplains. Floodplain maps are typically based on historical data and modeling to predict future flooding.

Floodplain determination involves analyzing hydraulic models to determine what is located in the area and the impact on floodplain elevations. Floodplain analysis is used to determine the floodplain boundaries, and floodplain maps are developed by the Federal Emergency Management Agency (FEMA) in collaboration with local communities. Floodplain maps are periodically revised by FEMA and adopted by local governments.

What about watersheds?

A watershed is an area of land that drains water into a particular river or stream. It is a region of land where water from rain or snowmelt drains downhill into a body of water, such as a river, lake, dam, estuary, wetland, or sea. Every body of water has a watershed, which can be small or large. Watersheds are often called drainage basins, and they are separated from adjacent basins by a perimeter, the drainage divide, made up of a succession of elevated features, such as ridges and hills. A basin may consist of smaller basins that merge at river confluences, forming a hierarchical pattern.

In Jackson County, Oregon, there are multiple watersheds draining into the Applegate Basin, the Bear Creek Basin, and the Upper/Middle Rogue River Basin. The region is subject to periodic flash flooding due to sudden heavy rains and snowmelt, causing waterways to exceed capacity and flood properties. As a participant in FEMA’s National Floodplain Insurance Program (NFIP), Jackson County applies additional regulations to development in the Special Flood Hazard Areas (SFHAs) within the watersheds.

Accessing Floodplain Maps in Jackson County

You can access FEMA’s Flood Insurance Rate Map panels (FIRM Panels) for Jackson County through the FEMA Flood Map Service Center (MSC). Additionally, Jackson County has floodplain overlay maps available through the mapping tool Jackson Interactive Mapping (JIM). These maps help mortgage lenders determine insurance requirements and help communities develop strategies for reducing their risk.

Disputing Floodplain Assessments

If you disagree with the floodplain assessment for your property, options are available to challenge the determination. You can submit a Letter of Map Change (LOMC) request to FEMA, which can be completed online or by sending paper forms by mail. You can seek two types of determination documents in your LOMC request: Letter of Map Amendment (LOMA) and Letter of Map Revision based on Fill (LOMR-F). If FEMA grants the map amendment or revision request, the property owner may no longer be required to pay flood insurance. The property owner can send the determination document to their lender and request that the federal flood insurance requirement for the structure be removed.

How Richard Stevens & Associates Can Help

Richard Stevens & Associates is a land use consulting firm located in Medford, Oregon, specializing in assisting clients with obtaining rural and urban land use planning permits. With a great working relationship with all counties and cities throughout Southern Oregon, we understand each planning department’s requirements for each land use application.

By working with Richard Stevens & Associates, you can ensure your floodplain determination and potential disputes are handled professionally and efficiently. Our expertise in land use planning and knowledge of local regulations will help you navigate the complex process of floodplain determination in Jackson County, Oregon, and the surrounding areas.