Wednesday, November 13, 2019

Zone A Phase II Floodplain Delineation Study

New Preliminary Flood Maps Provide Updated Understanding of County Flood Risks

The Yavapai County Flood Control District (the District) and the Federal Emergency Management Agency (FEMA) are processing a new Physical Map Revision (PMR) of several flood hazard areas within Yavapai County. These more detailed maps will help property owners better understand their flood risk and help them make more informed decisions on how to protect their family and property during a runoff event.

Why Remap?

The flood hazard areas in Yavapai County were originally mapped in the late 1970s. Over time, water courses have changed due to large rainfall events, erosion and development. In addition, development over the last several decades didn't always include managing the increased runoff into our watersheds. So, the County’s flood maps are being updated to show the current high and moderate-low flood hazard areas.

High-risk flood areas are shown on flood maps (known as Flood Insurance Rate Maps, or FIRMs) as flood zones beginning with the letter “A” or “AE”. While Zone AE is based on detailed studies that include defining not only the floodplains but also floodways1 and Base Flood Elevations (BFEs)2, most of the County’s original flood studies were based only on approximate studies and therefore, BFEs and floodways were not shown. When BFEs are not available, the burden falls on the permit applicant to determine the true flood hazard area. In some cases, flood insurance could also be less expensive if BFEs were available instead of using approximate Zone A rates.

To help provide this additional detail as well as updated flood risk information, the District started a multi-phase study to remap hundreds of miles of Zone A and include Base Flood Elevations. The updated studies don’t have as much detail as Zone AE studies provide, such as floodways, but they do include Base Flood Elevations, as well as depths and velocities. This data is much less expensive to create and provides information that property owners would otherwise have to determine themselves (or do without when their flood insurance cost is calculated).

What Areas Are Being Updated in Phase 2?

The first phase of updating Zone A flood risk information and providing BFEs included the Big Chino Wash, Kirkland, and Date Creek areas among others. It was part of a bigger mapping study which became final on February 15, 2019.

This next Zone A study, which kicked-off in August 2015, covers numerous watercourses including streams and tributaries to Partridge Creek, Skull Valley Wash, and the Hassayampa River. Nearly 145 stream miles representing 90+ creeks, washes, rivers, and tributaries were studied.

When Will These New Maps Become Effective?

Zone A-Phase 2 Mapping Milestones

August 2015
  • Mapping project starts
August 2019
  • Preliminary flood maps issues for review
  • Community Official meeting with FEMA
  • Stakeholder and public meetings held
Fall-Winter 2019-2020*
  • 90-Day Public Comment Period
  • Appeals and comments addressed
Early 2020
  • Letter of Final Determination Issued
Summer 2020
  • New flood maps become effective as do flood insurance requirements for areas newly identified as high risk.

*Dates are subject to change

The District and FEMA held the first public open house to allow residents and business owners in the area being restudied to view the new maps and ask questions to FEMA, the District and mapping and insurance specialists. The 90-day public comment period started on November 1, 2019, which provides property owners, developers and the County the opportunity to review the maps and provide comments and even appeal them; however, to file an appeal, scientific and/or technical data must be provided. For more information on the appeal process, contact the District.

Once all appeals have been addressed and resolved, FEMA will issue a Letter of Final Determination to the County. This indicates the new maps and study will be effective in six months and that the County must pass an ordinance to adopt them for floodplain management use. Also, that is the time any changes in flood insurance due to changes in flood zone or BFE will become effective. The new maps are targeted to be effective in mid-year 2020.

Where Do I Go for More Information?

This web page is the primary source of information about the Zone A-Phase 2 mapping project and areas being studied. You can view up your property on the new preliminary maps by clicking on the Property Search Tool in the menu at the top of this page. If you want additional details, contact Lynn Whitman (District Director) at 928-771-3197 or email

For more information about flood insurance, contact your insurance agent or visit .

1 Floodway is the land immediately next to the river channel (or other waterway) that is the natural channel for floodwaters. Since the floodway must remain open in order to allow flood waters to pass, construction is typically limited in these areas.
2 Base Flood Elevations are the heights to which floodwaters are anticipated to rise during a major (base) flood, known as the 1-percent annual chance flood. A 1-percent annual chance flood can happen more than once in a year.

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