Annapolis Floodplain Information
National Flood Insurance Program and Floodplain Management
National Flood Insurance Program
The National Flood Insurance Program (NFIP) aims to reduce the impact of flooding on private and public structures. It does so by providing affordable insurance to property owners, renters and businesses and by encouraging communities to adopt and enforce floodplain management regulations. These efforts help mitigate the effects of flooding on new and improved structures. Overall, the program reduces the socio-economic impact of disasters by promoting the purchase and retention of general risk insurance, but also of flood insurance, specifically.
Floodplain Management: A floodplain is an integral part of the stream system. It provides storage capacity for high flows, helps reduce the erosive power of the stream during a flood, reduces the discharge of sediment during high flow periods and helps flood waters to move downstream. Floodplains also offer opportunities for wildlife habitat which can increase the biodiversity of a stream. The 100-year floodplain is that land area adjoining the stream that has a 1% or greater probability of flooding in any given year. Floodplains provide a stream with buffer and water quality benefits as well.
The Federal Emergency Management Agency (FEMA) has identified special flood hazard areas (SFHA) within the boundaries of City of Annapolis. Special flood hazard areas are subject to periodic inundation which may result in loss of life and property, health and safety hazards, disruption of commerce and governmental services, extraordinary public expenditures for flood protection and relief, all of which adversely affect the public health, safety and general welfare. Structures that are inadequately elevated, improperly floodproofed, or otherwise unprotected from flood damage also contribute to flood losses.
The City of Annapolis, by resolution, agreed to meet the requirements of the NFIP and was accepted for participation in the program on November 4, 1981. As of that date, the initial effective date of the City of Annapolis Flood Insurance Rate Map (FIRM), all development and new construction, are to be compliant with chapter 17.11 of the city code.
Flood Zones Explained
The following are areas that may be shown on Flood Insurance Rate Maps:
(1) Zone A: Special Flood Hazard Areas subject to inundation by the one-percent annual chance (one hundred-year) flood; base flood elevations are not determined.
(2) Zone AE and Zone A1-30: Special Flood Hazard Areas subject to inundation by the one-percent annual chance (one hundred-year) flood; base flood elevations are determined; floodways may or may not be determined. In areas subject to tidal flooding, the limit of moderate wave action may or may not be delineated.
(3) Zone AH and Zone AO: Areas of shallow flooding, with flood depths of one to three feet (usually areas of ponding or sheet flow on sloping terrain), with or without BFES or designated flood depths.
(4) Zone B and Zone X (Shaded): Areas subject to inundation by the 0.2-percent annual chance (five hundred-year) flood; areas subject to the one-percent annual chance (one hundred-year) flood with average depths of less than one foot or with contributing drainage area less than one square mile; and areas protected from the base flood by levees.
(5) Zone C and Zone X (Unshaded): Areas outside of zones designated A, AE, A1-30, AO, VE, V1-30, B, and X (Shaded).
(6) Zone VE and ZONE V1-30: Special flood hazard areas subject to inundation by the one-percent annual chance (one hundred-year) flood and subject to high velocity wave action (also see Coastal High Hazard Area).
Types of Flood Damage
Hydrodynamic forces - Moving water creates a hydrodynamic force which can damage a building's walls in three ways:
- Frontal impact, as water strikes the structure.
- Drag effect, as water runs along the sides of a structure.
- Eddies or negative pressures, created as water passes the downstream side.Source: Federal Emergency Management Agency. Unit 1: Floods and Floodplain Management. 2005. Publication 480 – Floodplain Management Requirements – A Study Guide and Desk Reference for Local Officials.
Debris impact - Debris also increases the hazard posed by moving water. Floodwaters can and will pick up anything that will float-logs, lumber, ice, even propane tanks and vehicles. Moving water will also drag or roll objects that don't float. All of this debris acts as battering rams that can knock holes in walls.
Hydrostatic forces - The weight of standing water puts hydrostatic pressure on a structure. The deeper the water, the more it weighs and the greater the hydrostatic pressure.
Soaking - When soaked, many materials change their composition or shape. Wet wood will swell, and if it is dried too fast it will crack, split or warp. Plywood can come apart. Gypsum wallboard will fall apart if it is bumped before it dries out. The longer these materials are wet, the more moisture they will absorb. Soaking can cause extensive damage to household goods. Wooden furniture may get so badly warped that it can't be used. Other furnishings, such as upholstery, carpeting, mattresses and books, usually are not worth drying out and restoring. Electrical appliances and gasoline engines won't work safely until they are professionally dried and cleaned.
Sediment and contaminants - Many materials, including wood and fiberglass or cellulose insulation, absorb floodwater and its sediment. Even if allowed to dry out, the materials will still hold the sediment, salt and contaminants brought by the flood. Simply letting a flooded house dry out will not render it clean-and it certainly will not be as healthy a place as it was before the flood.