If you are planning on building your dream home in North Scottsdale or Rio Verde, it pays to do your research early to find out if you are in or near a floodplain.
Many people don't realize it but there are mapped floodplains in the area that need to be considered in the development of parcels of land in North Scottsdale and Unincorporated Maricopa County (Rio Verde).
The Rio Verde watershed is located in Maricopa County, Arizona, and is generally bounded by the Tonto National Forest on the north, the McDowell Mountain Regional Park to the south, the Verde River to the east, and approximately the 115th Street alignment to the west.
The topography is rolling with a gradual downslope to the Verde River. As you can see from the area map below, this area drains into the Verde River.
The Flood Control District of Maricopa County oversees development in known "floodplain" areas. Typically the development process involves Maricopa County Planning and Zoning first and if they determine that your parcel is located within the FEMA 100 year floodplain, they require that you submit an application through the Flood Control District as well.
Most of the time, you can determine if a parcel lies within the FEMA 100 Year floodplain by utilizing the Floodplain Viewer and entering an address or intersection. This will give you a general idea about the flood risk associated with a property but it is best to consult with a professional engineer.
If a proposed improvement encroaches into the FEMA 100 year floodplain, it will require that a permit be obtained from the Flood Control District. This will require an application, a fee and likely a drainage report prepared by a professional engineer licensed in Arizona. The Drainage Report will determine the potential impact on waters upstream and downstream from the improvements. While it is an additional cost to the project, it can save money down the road and reduce potential headaches and costly "do-overs".
While it is best to avoid developing within the floodplain altogether, if it is unavoidable, then the slab elevation will have to be at least 2 feet above the FEMA 100 year floodplain elevation and their is a good chance that measures will need to be taken to avoid the erosion of the soil underneath the slab area. Additionally, if the lot falls within the FEMA 100 year floodplain, homeowner's insurance will require that a flood insurance rider be placed on the policy as well.
Floodplains are just part of the complicated nature of development within the Rio Verde Area. Want to know more about building a home on an acreage in Unincorporated Maricopa County? Give me a call.
While at Dibble Engineering, Dan Frank was the Project Engineer for the Rio Verde Area Drainage Master Plan and later served as the Project Manager and QA/QC supervisor for the Rio Verde ADMP Floodplain Delineation FEMA Submittal.
Technical information:
The computer modeling of the study area is accomplished by using a combination of one-dimensional and two-dimensional methodologies. The one-dimensional modeling is accomplished using the HEC-I computer model for hydrology and the HEC-RAS computer model for hydraulics. The two-dimensional modeling uses a single program, FLO-2Dto model both hydrology and hydraulics.
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