Modesto | Flood Zones and Landmarks

Modesto Flood Zones and Landmarks: Floodplain Permits, Floor Heights, Floodways and Landmark Review

Two Modesto rule sets sit on top of zoning and can change what a lot will hold. Title 9, Chapter 4 of the Municipal Code controls building in flood zones, and Title 9, Chapter 10 protects designated landmarks. Both add a review to the normal permit, both can block a plan the zone allows, and both also limit the state SB 9 routes. This page explains each rule as written in Supplement 72. The Modesto overview sums up the whole guide.

Which Land the Flood Rules Cover

Chapter 4 was adopted by Ordinance No. 3430-C.S., effective January 4, 2007. Section 9-4.102 says the City's flood hazard areas "are subject to periodic inundation which results in loss of life and property." Section 9-4.301 applies the chapter "to all special flood hazard areas within the City limits."

A special flood hazard area is land the Federal Emergency Management Agency (FEMA) maps as having a 1 percent or greater chance of flooding in any year. Section 9-4.302 adopts FEMA's "Flood Insurance Study (FIS) for City of Modesto, California, Stanislaus County" dated August 15, 1980, its Flood Insurance Rate Maps and Flood Boundary and Floodway Maps, "and all subsequent amendments and/or revisions." The study and maps are on file at 1010 10th Street, Suite 4100. The base flood is "a flood which has a one (1) percent chance of being equaled or exceeded in any given year (also called the '100-year flood')," and the base flood elevation is the height its water reaches, shown on the map for zones AE, AH and A1 to A30.

Section 9-4.401 names the Chief Building Official as Floodplain Administrator. Under Section 9-4.402, that official checks every permit, decides whether work is a substantial improvement, and makes sure "the site is reasonably safe from flooding." Section 9-4.305 warns that larger floods "can and will occur on rare occasions," and that the chapter does not promise land outside the mapped areas will stay dry.

Building Rules in a Flood Zone

Sources: Modesto Municipal Code 9-4.301 and 9-4.302, 9-4.403, 9-4.501 and 9-4.506, Supplement 72.

Section 9-4.403 requires a building permit "before any construction or other development, including manufactured homes, begins within any special flood hazard areas." Development is "any man-made change to improved or unimproved real estate," including grading, paving and fill. The plans must show existing and proposed buildings, grading and fill, the base flood elevation, and the "Proposed elevation in relation to mean sea level, of the lowest floor (including basement) of all structures."

Section 9-4.501 sets the standards. Every new building is anchored against floating or collapse and built with flood-resistant materials below the flood level. For homes in zones AE, AH and A1 to A30, the lowest floor, including basement, must be "elevated to or above the base flood elevation." In a zone A with no mapped elevation, the Floodplain Administrator obtains one from other sources. When the building is done, "the elevation of the lowest floor ... shall be certified by a registered civil engineer or licensed land surveyor."

A fully enclosed space below the lowest floor, used only for parking, entry or storage, must let floodwater in and out. The rule is "a minimum of two (2) openings on different sides having a total net area of not less than one (1) square inch for every square foot of enclosed area," with the bottom of each "no higher than one (1) foot above grade," or an engineer's certified design. An attached garage may sit below the base flood elevation if it meets that opening rule and uses flood-resistant materials below that level.

Additions, Floodways and Subdivisions

Older homes are caught when work gets large. Section 9-4.201 defines a substantial improvement as any rebuilding, addition or other improvement "the cost of which equals or exceeds fifty (50) percent of the market value of the structure before the 'start of construction' of the improvement." Substantial damage is damage of the same size. Either one brings the whole building under the new construction rules. Market value is set by City procedures based on FEMA Publication 213, under Section 9-4.402(b).

A floodway is "the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than one (1) foot" (Section 9-4.201). Section 9-4.506 calls floodways "an extremely hazardous area." In an adopted floodway, fill, new construction and substantial improvements are barred "unless certification by a registered civil engineer is provided demonstrating that the proposed encroachment shall not result in any increase in flood levels." Where no floodway is adopted, in zones A1 to A30 and AE, a project may not raise the base flood "more than one (1) foot at any point within the City of Modesto" when added to all other development.

New lots face two rules. Section 4-4.302(d)(4) says "No land subject to flooding ... shall be plotted for residential occupancy." Section 9-4.503 requires every subdivision to identify flood areas and base flood elevations and show "the elevations of lowest floors of all proposed structures and pads on the final plans." Where a site is filled above the flood level, the engineer certifies the floor, pad and lowest ground elevations for a FEMA map revision based on fill. Under Section 9-4.402, grading permits rest on FEMA's conditional approval of a map change, and building permits wait for the final one.

Flood Variances and Appeals

A variance is permission to depart from a rule. Section 9-4.601 says the goal of reducing flood loss "can only be met if variances are strictly limited," because of the cost of insuring a building below flood level. Under Section 9-4.602, the City Council hears each request after mailing notice to owners within 300 feet. Section 9-4.603 says variances "may be issued for new construction ... on a lot of one-half (½) acre or less in size contiguous to and surrounded by lots with existing structures constructed below the base flood level." None may be issued in a floodway if flood levels would rise.

An owner who gets a variance is told in writing that building below the flood level raises flood insurance rates "up to amounts as high as twenty-five dollars ($25.00) for one hundred dollars ($100.00) of insurance coverage," and that notice is recorded on the title. A denied request cannot be filed again for one year. Any other decision of the Floodplain Administrator may be appealed to the City Council (Section 9-4.404).

Modesto Landmarks

The City's Landmark Preservation Program page says "Modesto established its Landmark Preservation ordinance in 1988, following the demolition of many beautiful old buildings in downtown." The rules in force today are Chapter 10 of Title 9, added by Ordinance No. 3691-C.S., effective March 7, 2019. A Modesto Landmark Preservation Site is "An area, district, building, structure or object, which has been designated for preservation for reasons of its significance by the City Council."

The Landmark Preservation Commission has five or seven members appointed by the City Council under Section 1102 of the Charter, each a registered voter living in Modesto. It surveys properties, holds a public hearing on each nomination, and recommends sites. The Council designates them by resolution, and the City Clerk records each designation with the Stanislaus County Recorder (Section 9-10.05). The Commission keeps a public list of designated sites, places on the State or National Register, and places in a historic resource survey.

Landmark Permit Review

Section 9-10.07 covers building permit applications "which propose to alter, renovate, or demolish landmarks or landmark-eligible resources." The Chief Building Official refers the permit to the Community and Economic Development Director, and "No building permit shall be issued until the Landmark Preservation Commission issues written approval or the Director indicates that the resource is not subject to review." Alteration includes "remodeling, repair, signs or fences that will change the exterior appearance." Demolition "may include the whole or any part of a building."

The Commission holds a public hearing, with notice mailed at least 10 days ahead to owners within 300 feet and to the school districts. For an addition, it asks whether original qualities are destroyed; "Contemporary design for alterations and additions to existing properties shall not be discouraged" when it fits the size, scale and materials of the building. For a demolition, it weighs the building's significance, its value and replacement cost against the new project, its structural safety, and the effect on the neighborhood. New buildings "should be compatible with the height, width, depth, massing and setback of the surrounding buildings."

• Deadline. If the Commission has not acted "within forty-five (45) days from the filing of the completed application," the permit "shall be deemed to have been approved." It may add 15 days when a professional study is needed.
• Building code. Where the Commission's advice conflicts with the California State Historical Building Code, the state code prevails.
• Emergencies. The Chief Building Official may approve temporary repairs to protect safety without prior Commission action.
• Appeal. The applicant or anyone aggrieved may appeal to the City Council within 15 days of the decision.
• Penalty. Each day of work in violation is a separate infraction, and the work is declared a nuisance (Section 9-10.08).

Source: City of Modesto, Planning Division Fees, effective July 1, 2026 through June 30, 2027, due at time of application.

How Landmark Status Affects More Homes

Landmark status reaches several other rules. Section 4-4.305 says a tentative or parcel map that includes a landmark site "will be deemed complete only when proof of project approval by the Landmark Preservation Commission has been submitted." Downtown, Section 10-7.515 bars relocating or demolishing a building on the National or California Register or a designated Landmark Preservation Site except under Chapter 10, and requires that new buildings next to a historic site be "no greater than two (2) stories higher or lower than the historic building."

The state SB 9 routes stop at landmarks. Government Code 65852.21 does not apply to "a property individually designated or listed as a city or county landmark under a city or county ordinance," or to a contributing structure in a historic district. Government Code 66411.7 bars an urban lot split on "a site that is designated or listed as a city or county landmark." The City's R-1 duplex rule has no such bar, but Section 9-10.07 review still applies to any alteration or demolition.

ADUs get some relief. Section 10-4.508 requires no ADU parking "within an architecturally and historically significant district," and Section 10-4.503 requires notice before a garage is torn down for an ADU only in such a district or on a listed property. Owners of a designated site may apply for a Mills Act contract under Section 9-10.10, which the City's Local Preservation Ordinances page describes as "a small reduction in property tax in exchange for preservation and maintenance."

Where the Code Disagrees With Itself

• Small accessory buildings in a flood zone. Section 9-4.201 defines a low-cost and small accessory structure as "Less than one hundred fifty (150) square feet," yet Section 9-4.501(c)(5) allows a detached garage or storage building of that kind "not larger than 600 square feet." The code does not say which number controls, so confirm with the Floodplain Administrator before you place a garage floor below the flood level.

Where to Go Next

Related on VanPlex: the Modesto overview and the property tax and insurance page.

Frequently Asked Questions

Official sources (checked October 2026)