Boise City is crossed by a large freestone river and several
foothills gulches that are susceptible to annual flooding events
that pose threats to life and safety and can cause significant
The Boise River system drains a very large area on the west and
south sides of the Sawtooth Mountains. Although three dams
(Anderson Ranch, Arrowrock and Lucky Peak) control the release of
water, unusual climatic events such as heavy winter snowfall and
warm wet springtime conditions can and have caused release rates
from the dams to be high enough to create widespread local flooding
in the Boise area.
In addition, sudden and severe thunderstorms over the foothills
can cause flash flooding on the various gulches that drain into the
Boise urbanized area. Ongoing development within the City and
County continues to displace natural areas that have historically
functioned as flood storage.
Boise City participates in the National Flood
Insurance Program (NFIP) that makes federally backed
flood insurance available for all structures, whether or not they
are located within the floodplain.
Maintaining the flow capacity in streams that cross City
properties requires cooperation and assistance to prevent flooding
and bank erosion. Following are some suggestions and information
for understanding the ways that floodplains function and how the
City regulates the floodplain in order to protect property and
lives, while affording citizens the ability to obtain floodplain
Contact the Boise City Planning & Development Services
Department at (208) 384-3830 for further information.
During Boise's typical hot, dry summer it is difficult to
envision flooding as a problem. However, for those that live in or
directly below the foothills gulches, flash flooding related to
thunderstorms is possible this time of year. In the spring,
flooding of the Boise River becomes a possibility. Extensive
property damage and even loss of life can occur from flooding.
Property owners in a designated Special Flood Hazard Area (SFHA)
should make every effort to protect themselves and their property
from flood loss.
The Flood Insurance Rate Map (FIRM) for the City of Boise
identifies properties that are within or in close proximity to
special flood hazard areas (SFHA) that are subject to flooding.
Such areas are associated with the floodplain of the Boise River
and Boise River tributaries including foothills gulches such as
Cottonwood Creek, Crane Creek, Hulls Gulch, Sand Creek (Stuart
Gulch) and Squaw Creek. The Boise River and its tributaries, as
well as the various foothills gulches have all caused damaging
flooding in past years and will inevitably do so again.
National Flood Insurance Program and Community Rating
The City of Boise is an active participant in the National Flood
Insurance Program (NFIP), which enables owners of property within
floodplain areas to purchase flood insurance. The City also
participates in the Community Rating System (CRS) Program, which
rates the community's performance in administering the
The City's Planning & Development Services Department (PDS),
located on the second floor of City Hall, maintains copies of the
current FIRM, which were effective February 19, 2003. Copies of the
current FIRM and other floodplain documents are also available at
the public library. PDS Staff is available to assist the public in
determining whether or not specific properties are within a SFHA.
We can also help you determine the estimated depth of flooding in
Mortgage lenders generally require flood insurance for properties
within a SFHA. Citizens that own property outright are not required
to purchase flood insurance and some elect not to, primarily
because of the cost of the insurance premiums. All properties
within SFHA should be covered by flood insurance as the primary
protection against loss of property from flooding.
Mitigating Flood Damage
In addition to purchasing flood insurance, there are physical
improvements that can be made to mitigate the damage from flooding.
In some cases, it may be financially feasible to raise or elevate a
structure so that the lowest floor is above the base flood
elevation. There are also methods for dry flood-proofing structures
so that all portions of the building below the base flood elevation
are made watertight. Certain properties may also have options of
physically raising structure openings such as window wells or
constructing berms around the foundation.
Several documents on flood protection are on file at the Boise
Public Library including "Homeowner's Guide To Retrofitting (Six
Ways To Protect Your House From Flooding)."
Thank you for maintaining an awareness of the potential hazard
from flooding in our community. Please feel free to contact the PDS
Staff at 384-3830 should you need information or assistance with