3.2.6 Floodplain

Flooding effects may range from personal nuisance to property damage or loss to injury or death.  Floodplain areas flood most often and severely.  Land use regulations define the floodplain as the area covered by the flood that has a one percent chance of occurring each year, also known as the 100-year flood.  The floodplain is divided into two zoning districts: the floodway and flood fringe.  The floodway includes the river channel and nearby land areas which must remain open to discharge the 100-year flood.  The flood fringe, while in the flood plain, lies outside the floodway.  Regulations usually allow development in the flood fringe but require flood-proofing or raising to the legal flood protection elevation.

In 1968, Congress created the National Flood Insurance Program (NFIP) to make flood insurance available to property owners at federally subsidized rates.  The NFIP required communities to adopt local laws to protect lives and future development from flooding.  The Federal Emergency Management Agency (FEMA) first must formally notify a community that it has special flood hazard areas (SFHA) before it can join the NFIP.  FEMA notifies communities by issuing a Flood Hazard Boundary Map (FHBM).  This map shows the approximate boundaries of the community's 100-year flood plain.  Each participating community has a special conversion study or a Flood Insurance Study (FIS).  The FIS includes a flood plain map depicting the community's flood hazard areas.  Flood mapping was recently updated for all communities in Hennepin County.

Table 21.  Status of flood mapping for communities in the MCWD participating in the National Flood Insurance Program.

Community

Initial FIRM

Current Effective Map

Deephaven

9/2/04

9/2/04

Edina

5/1/80

9/2/04

Excelsior

12/1/77

9/2/04

Golden Valley

2/4/81

9/2/04

Greenwood

9/2/04

9/2/04

Hopkins

5/5/81

9/2/04

Independence

1/6/83

9/2/04

Long Lake

9/2/04

9/2/04

Maple Plain

9/2/04

9/2/04

Medina

9/3/80

9/2/04

Minneapolis

1/18/81

9/2/04

Minnetonka

5/19/81

9/2/04

Minnetonka Beach

9/2/04

9/2/04

Minnetrista

9/27/85

9/2/04

Mound

9/29/78

9/2/04

Orono

10/17/78

9/2/04

Plymouth

5/15/78

9/2/04

Richfield

9/2/04

9/2/04

St. Bonifacius

9/2/04

9/2/04

St. Louis Park

6/1/77

9/2/04

Shorewood

12/4/79

9/2/04

Spring Park

5/1/79

9/2/04

Tonka Bay

5/1/79

9/2/04

Wayzata

11/1/79

9/2/04

Woodland

8/1/79

9/2/04

Chanhassen

11/9/73 (FHBM)

NSFHA

Laketown Township

2/1/78*

1/6/88*

Victoria

6/7/74 (FHBM)

NSFHA

Watertown Township

2/1/78*

1/6/88*

*Carver County.  FIRM = Flood Insurance Rate Map; FHBM = Flood Hazard Boundary Map;  NSFHA = No Special Flood Hazard Area – all Zone C

Source:  FEMA Community Status Book Report.

In 2005 the District completed an evaluation of flood elevations on Minnehaha Creek, and four upper watershed streams: Gleason Creek, Long Lake Creek, Painter Creek, and Six Mile Creek.  The results of those evaluations are indicated on floodplain maps in the respective subwatershed plan.  See Figure 30 for floodplain locations in the watershed.