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North Ranch Wash Floodplain Remapping

Study status: 
Completed - Existing conditions local floodplain delineations
Completed - FEMA floodplain map revision

Study/Project Purpose

For more information contact:
Evan Canfield, PE, PhD, CFM Project Manager
(520) 724-4600

The purpose of this project was to perform a floodplain study for the portion of the North Ranch Wash starting at the Oasis Road alignment and continuing upstream (north) to a point located north of W. Tortolita Mountain Circle. Segments of the study reach are located in both the Town of Oro Valley and unincorporated Pima County. The information provided by the study provided the technical support for a Letter of Map Revision (LOMR) approved by FEMA. That LOMR (Case # 20-09-1981P) has an effective date of June 23, 2021. For more information on LOMR’s see this Frequently Asked Questions brochure

Project Location

The contributing watershed for the study reach of North Ranch Wash is bounded at the downstream limit by the Oasis Road alignment and extends northerly to the headwaters within the Tortolita Mountains. The watershed is located within portions of the following Townships and Range in Pima County, Arizona:

 The study reach for the floodplain mapping corresponds to the FEMA floodplain boundaries shown on the 2011 Flood Insurance Rate Maps (FIRMs) beginning downstream at the Oasis Road alignment and continuing to the upstream limit where the FEMA mapping terminated at a point located north of W. Tortolita Mountain Circle. The study reach is shown on the attached map provided by the RCFD. The study reach is approximately 7 miles in length. The FEMA Special Flood Hazard Areas (SFHA), shown on the 2011 FIRMs, mostly consisted of Zone A (approximate mapping), with a local area of Zone AE (detailed mapping) located just south of Tangerine Road.

Maps

Project Location and Boundary Map

Project Description

This project was performed in a cooperative technical partnership between the Pima County Regional Flood Control District and the Town of Oro Valley. FEMA has identified Special Flood Hazard Areas (100-year floodplains) associated with the washes which encompass homes and businesses. The North Ranch Wash floodplain is complex and exhibits two-dimensional flow patterns, and the District and Town of Oro Valley  the previous floodplain maps did not accurately reflect risk. New two-dimensional floodplain assessment techniques with improved topographic information were used to develop new detailed mapping to define that risk.

FEMA Floodplain Map Revision

The previous North Ranch Wash floodplain limits shown on the Flood Insurance Rate Maps (FIRMs) were outdated. The Pima County Regional Flood Control District submitted a Letter of Map Revision (LOMR) application to the Federal Emergency Management Agency (FEMA) to modify the floodplain boundaries. FEMA approved the LOMR (Case #20-09-1981P) on February 8, 2021, with an effective date on June 23, 2021. Click in the map boundary boxes in the image below to compare the exiting FIRM flood hazard boundaries (from 2011) to the proposed boundaries submitted with the LOMR. The proposed floodplain limits will become effective on June 23, 2011.

Clickable index map for North Ranch Wash floodplain maps North Ranch Floodplain Map 1 North Ranch Floodplain Map 2 North Ranch Floodplain Map 3 North Ranch Floodplain Map 4 North Ranch Floodplain Map 5 North Ranch Floodplain Map 6 North Ranch Floodplain Map 7 North Ranch Floodplain Map 8 North Ranch Floodplain Map 9 North Ranch Floodplain Map 10 North Ranch Floodplain Map 11 North Ranch Floodplain Map 12 North Ranch Floodplain Map 13 North Ranch Floodplain Map 14

North Ranch Floodplain Map 1
North Ranch Floodplain Map 2
North Ranch Floodplain Map 3
North Ranch Floodplain Map 4
North Ranch Floodplain Map 5
North Ranch Floodplain Map 6
North Ranch Floodplain Map 7
North Ranch Floodplain Map 8
North Ranch Floodplain Map 9
North Ranch Floodplain Map 10
North Ranch Floodplain Map 11
North Ranch Floodplain Map 12
North Ranch Floodplain Map 13
North Ranch Floodplain Map 14
LOMR Document