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Mary Guokas Montana Department of Natural Resources and Conservation.

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Presentation on theme: "Mary Guokas Montana Department of Natural Resources and Conservation."— Presentation transcript:

1 Mary Guokas Montana Department of Natural Resources and Conservation

2 Which one makes a bigger flood? Wetland (Sponges) Parking Lot

3 1964 Flathead County Flooding: In Evergreen, the water came up to La Salle Road (now U.S. 2). Getting from Woodland Park to East Reserve Drive required a boat. Photo credit: Possibly Daily Inter Lake Newspaper.

4 Flooding causes hardship and a lot of extra work Flathead County. Photo source: Unknown

5 Montana Department of Natural Resources Floodplain Management Program

6 What is a floodplain?

7 An area that could flood.

8 Floodplain near Lolo Creek in Ravalli County. Direction of flow. Lolo Creek going toward the Bitterroot River. Floodplains may not appear to be at risk of flooding. Floodplain Management

9 Same floodplain as previous photo with water added, during a 10- year flood event, a relatively minor flood event. May, But even adding a small amount of water can put them at risk. Floodplain Management

10 Depending on the shape of the floodplain, carrying capacity of the river, etc. generally… A 100-year flood event (1% chance flood event) could be far more extensive. A 500-year flood event (0.2% chance event) could be really extensive! No flooding. Flooding during a minor, approximate 10-year flood event. Floodplain Management

11 What is a floodplain? Some floodplains are called Special Flood Hazard Areas (SFHA) by FEMA, many people commonly call these 100- Year Floodplains. Special Flood Hazard Area 100-Year Floodplain

12 What is a floodplain? The term 100-year floodplains can be a misnomer as flooding in these floodplains may occur more or less often than 100 years. Special Flood Hazard Area 100-Year Floodplain

13 What affects the severity of a flood? 2011Twin Bridges, Montana. Photo credit: Madison County DES

14 What affects the severity of a flood? Rain Snowmelt 2011Twin Bridges, Montana. Photo credit: Madison County DES

15 What affects the severity of a flood? Rain Snowmelt Frozen Ground 2011Twin Bridges, Montana. Photo credit: Madison County DES Water cant penetrate frozen ground.

16 What affects the severity of a flood? Rain Snowmelt Frozen Ground Recent Fires 2011Twin Bridges, Montana. Photo credit: Madison County DES Water cant penetrate frozen ground.

17 What affects the severity of a flood? Rain Snowmelt Frozen Ground Recent Fires Types of Groundcover 2011Twin Bridges, Montana. Photo credit: Madison County DES Water cant penetrate frozen ground.

18 What affects the severity of a flood? We cant do much about these: Rain Snowmelt Frozen Ground Recent Fires 2011Twin Bridges, Montana. Photo credit: Madison County DES Water cant penetrate frozen ground.

19 What affects the severity of a flood? We may be able to do something about types of groundcover 2011Twin Bridges, Montana. Photo credit: Madison County DES Water cant penetrate frozen ground.

20 Natural Ground Cover i.e. Wetlands Whats the percent runoff with Natural Ground Cover? Above and following illustration based on Stream Corridor Restoration: Principles, Processes, and Practices 10/1998, by the Federal Interagency Stream Restoration Working Group.

21 Runoff associated with Natural Ground Cover =10%

22 Impervious Surface: Hard surface like concrete

23 Runoff associated with 10% to 20% impervious surfaces =20%

24

25 Runoff associated with 35% to 50% impervious surfaces 30%

26 A Very Impervious Surface i.e. Parking Lot Whats the percent runoff on a Very Impervious Surface?

27 Runoff associated with Very impervious surfaces =55%

28 Over natural ground cover such as wetlands, about 10% of precipitation runs across the land and may result in small floods. Over developed land surfaces where parking lots exist, 55% of the precipitation may run across the land, which likely results larger floods.

29 Using a stream gauge to measure flooding severity.

30 ?

31 5.10

32

33 4.96

34 ?

35 5.24

36 Floodplain Simulator Activity

37 Entering data into spreadsheet with different flooding scenarios.

38 Completed spreadsheet.

39 Hydrograph created from data in spreadsheet.

40 Blank data sheet is used to enter data as a backup to data entered on spreadsheet.

41 Students from Mr. Sleads class making observations during a flooding simulation. Helena. Student reading the stream gauge during a simulation. Student explaining a hydrograph created from simulations, to fellow students.

42 Dr. Vicki Miller, University of Montana Building in a floodplain is like pitching your tent on a highway when there are no cars coming. Is there an alternate place to build?


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