ready for record runoff?local.sltrib.com/upload/2011/05/1304573231warmfloodpageb.pdfm ost san dbags...
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Sandbagging is a seasonal ritual in flood-prone cities and towns. Millions of bags are filled, readied and made into levees according to methods developed for saving lives, homes and property. Here’s a look at how it’s done.
Sandbags
Incorrect
Correct
Filling bags
Sandbagging 101
How to shore up structures to resist high water
Most sandbags are made of woven polypropylene and are 14 inches wide and perhaps 2 feet deep; they’re usually filled about halfway with sand or clay and tied or stapled; they weigh about 35 pounds.
It usually takes two people to fill one sandbag; crews often use funnels (like the one shown), but mass production sometimes involves conveyors and chutes.
Site prep
Water flow
1 bag deep,two wide
Site preparation begins with scraping away ice, snow and topsoil, if possible;a shallow trench sometimes helps hold the levee in place.
Levees are usually built at least a foot higher than the predicted crest of the water.
The U.S. Army Corps of Engineers recommends that a levee have a base three times wider than its height; other sources say a 1:2 ratio is adequate for a solid levee. Bags are staggered, like bricks in a wall; the water’s weight helps hold a levee in place.Layers
of bagscompresstogether
Bondingtrench
The levee Construction ratios
Watertight
Plastic sheets are often wrapped under and over levees to prevent seepage.
NOTE: Floodwater is polluted, so used sandbags are considered contaminated
Plastic sheeting
Staggered rows
Water flow
Floodwater
1’(30 cm)
2’(61 cm)
3’(91 cm)
4’(122 cm)
5’(152 cm)
2’(61 cm)
4’(122 cm)
6’(183 cm)
8’(244 cm)
10’(305 cm)
Salt Lake County flood preparedness information includes these tips for preparing homes and structures for high water.
Across northern Utah’s mountains, snowpack measured as water equivalent t is well above normal and far above the levels recorded last water year.
*Water content of the snowpack measured in inches.
At Tony Grove at the headwaters of the Logan River, the snowpack is 172 percent of normal.
At Bug Lake near the Monte Cristo Range and the head- waters of the Blacksmith Fork, snowpack is also above normal.
At the headwaters of Chalk Creek in the Uinta Mountains, snow levels kept climbing in April to 160 percent of normal.
At Lookout Peak, snowpack stands at 221 percent of normal.
At the Mill D station near the
headwaters of Big Cottonwood Creek
in the Wasatch Range, another big
snowpack awaits.
1 2 3 4 5LoganRiver
Blacksmith Fork
Weber River/ Chalk Creek
Emigration Creek
Big Cottonwood Creek
Source:s: National Weather Service, Salt Lake County, Salt Lake City, MCT Regional elevation graphic reported, created by Todd Adams | The Salt Lake Tribune
Sandbagging 101 graphics | McClatchy-Tribune
Record snowpack
73
67
60
53
47
40
33
27
20
13
80 inches*
191
173
156
139
121
104
87
69
52
35
208 percent
171% of normal
Current water year
30-yearaverage
2010 water year
Doors and Nail
boards lengthwise across door frames, keeping
them as tight as possible.
Plywood works good on window frames. Make sure they’re covered high enough to withstand the debris flow.
To channel water away from structures, create a wooden berm that is reinforced with stakes that extend into the ground. Backstop the berm as shown in the drawing.
46 inches* 210 percent
167% of normal42
38
33
29
25
21
17
13
8
4
191
172
153
134
115
96
76
57
38
19
FEB MAR APR MAY FEB MAR APR MAY FEB MAR APR MAY FEB MAR APR MAY FEB MAR APR MAY
46 inches* 176 percent
162% of normal42
38
33
29
25
21
17
13
8
4
160
144
128
112
96
80
64
48
32
16
64 inches* 258 percent
58
52
47
41
35
29
23
17
12
6
235
211
188
164
141
117
94
70
47
23
223% of normal
46 inches* 176 percent
42
38
33
29
25
21
17
13
8
4
160
144
128
112
96
80
64
48
32
16
170% of normal
A large snowpack could bring trouble downriver if temperatures in coming weeks warm quickly.
Big runoff from a wet April may have been just a harbinger of things to come if May brings warm temperatures.
Farmlands along the lower stretches of the Weber already saw high water. The Oakley area upstream also could get deluged.
Heavy rains in April sent Emigration over its banks — and a big snowpack still awaits. City Creek, too, could see big runoff if May heats up quickly.
Residents along the creek that roars out of the canyon into the Salt Lake Valley already know the effects of high water; flood-control efforts will help — whether they’re enough, only time will tell.
SALTLAKE
CITY
OGDENLAYTON
OAKLEY
SANDY
Lower Weber Riverinundated farmlandswhen levee wasoverwhelmed in April.
Heber Valley streamsand waterways couldsee over-bankful conditions.
Five potential problem spotsFrom theheadwatersof theLogan Riverto the slopes ofthe WasatchRange, abig snowpackis poisedto letgo.
For up-to-date advisories and forecastsOn the web, go to the National Weather Service’s forecast center at http://www. wrh.noaa.gov/slc/ for the latest advisories.
Where to find help in your regionFor sandbags and flood help:Cache County
435-755-1059Salt Lake County
801-468-2711
801-483-6700, ext. 1
801-829-0590
Agencies, counties offer online help
River Forecast Center at http://www. cbrfc.noaa.gov/ has the latest river conditions.
County website at http:// www.pweng. slco.org/flood/ has information about flood abatement efforts, including real-time stream flows and historical data.
sheriff’s office has an online site dedicated to flood control efforts at http://www. cachesheriff.com/services/eoc/Flood_Info. htm
Morgan counties, the Weber Area Dispatch 911 and Emergency Services District has website at http://www.weber911.org/contact.htm with contact information.
Ready for record runoff?Here’s a guide to help stem the tide
Record snowpack, a wetter- and colder-than-normal spring and potential for a rapid warmup are conspiring to make this year’s seasonal runoff one big headache for people living near northern Utah’s rivers and streams. What can you do to protect yourself and your property? We offer a look at problem areas, some guidance on preparations and resources for getting help.