Flood Protecting Your Home

This page provides some information to assist you with information to help you protect your Home or Cottage. Before reading, remember we’re volunteers here, and not experts(see Disclaimer section of website):

NOTE: Sandbag Dikes were ineffective against the May 31st storm. Other alternatives such as stone walls might be more appropriate for future storms.

How do I build a Sandbag Dike:

Click on this link below to find out how to build a Sandbag Dike:
http://www.gov.mb.ca/emo/home/prepare/sandbag.html

How Do I get Sandbags?
Sandbags are currently available at the fish shack, and the honey processing shed at the channel.

If you don’t have a means to pick them up and haul them yourself:
Call Heather Greenlay at the RM – 857-4439 and she’ll help steer you in the right direction towards getting sandbags delivered to your backdoor.

Need Help Sand bagging?
You’ve got to be at your home if you want to sandbag. Lots of legal reasons why, and Volunteers need a leader…that’s you! Call the RM of Portage la Prairie at 204-857-4439 or 204-857-3821 and let them know you are looking for help. You are not alone, there are lots of people willing to help.

How do I build a stone wall?

Stone wall construction requires heavy equipment and engineering. It is recommended that the services of a contractor be engaged to construct a stone wall.

How High Do I need to be?
That is the million dollar question. There seem to be four factors to consider:

  1. Estimated Water Flood Level;
  2. Estimated Wind Set-up(often called Wind Tide);
  3. Estimated Wave Height;
  4. Some type of a safety factor.

This website is not an authority on these items, however, the following links may help you in determining your own idea on what height you need to be at:

  • Estimated Water Flood Level – Manitoba Water Stewardship’s June 30th Flood report states 817.8 is the current worst case forecast. For the most current report go to: http://www.gov.mb.ca/waterstewardship/floodinfo/forecasts_reports.html#daily_flood_reports
  • Estimated Wind Set-up(often called Wind Tide) – Manitoba Water Stewardship has provided an estimate of Wind Set-up for what a sustained North Wind of 60 km/h would do to Lake level including Wind Set-upthe South Basin(Note: This is basically what we at the beach often call Wind Tide). Basically a 3 foot Wind Set-up(Wind Tide).Here is where this information is located: http://www.gov.mb.ca/waterstewardship/floodinfo/forecast_centre/maps/inundation_maps/rm_portagelaprairie.pdf
  • Estimated Wave Height – In the May 18th Flood report, Manitoba Water Stewardship reported:During high winds, individual properties and dikes will be impacted by wave action differently. There are a number of factors that will change the way wind and the resulting wave action impacts properties and dikes, including: the slope of the shore, the distance from the water, obstructions that may buffer waves (roads, vegetation, etc.), the slope and height of flood protection dikes, and the depth of standing water against the dike.
    • Waves will generally be higher and have more energy if the beach is shorter and has a greater slope. Waves will generally be lower and have less energy if homes are located far from the normal lake edge, have a gently sloping beach or are travelling over flooded vegetation or other obstructions. Homes with a gently sloping beach could experience waves as high as 3 ft.
    • The impact of waves on dikes is dependent on the depth of standing water against the dike and the slope of the dike. With a sustained 60 km/hr offshore wind:
    o Sandbag dikes close to the water’s edge may experience waves as high as 3 ft
    o Sandbag dikes with water reaching the base of dike may experience waves as high as 4 ft
    o Sandbag dikes with water reaching part way up the dike are likely to experience waves as high as 7 ft.
    o Clay dikes are generally built with a gentler (5:1) slope when compared to the slope of sandbag dikes (1:2), dissipating the energy of the wave and reducing wave height.
    • Wave action is not illustrated on the inundation maps due to the site-specific circumstances of each property.
  • Some type of a safety factor. Manitoba’s Sandbag Dike brochure suggests a 2 foot of freeboard.

So an example of how all this works, assuming:

  • Lake Level of 817.5 feet
  • Wind Set-up of 3 feet
  • Wave height of 3 feet
  • Freeboard of 2 feet
    817.8 + 3 + 3 + 2 = 825.8 feet is height sought

Now, for this example, if you’re elevation is:

  •  Above  825.8, you would be OK
  • Below 825.8, you might want to consider increasing “height” through a Dike. For example, if I am at 820, I would build a Dike of 5.8 feet, and I would then be at 825.8

Elevations
Owners are encouraged to post any Elevations they might know below as “comments” so others may have an idea. PLEASE NOTE TO ALL: This information is being provided without any guarantee or warranty.

The RM Planning office did advise the top northwest ledge of the Channel Bridge is 815.7 feet.

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One Response to Flood Protecting Your Home

  1. Hi Scott, I have a copy of a survey done of our lot in 1999 by David McBurney. It shows the elevation of the west side of our lot at the road at 18 Hackberry East as being:

    “Elevation on top of 1/2″ SQ. I.P. = 815.9′ ”

    Also on the hydro pole between our cottage and Ramseys’ cottage it states: “Elevation of spike in base of hydro pole = 818.75′ ”

    Joan Farncombe

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