Flood Control | New Mexico Dirtbags

Rising Water

Slowly rising water without a strong current or flow is the easiest to control. This might be caused by heavy rains that aren't draining fast enough or properly (and threatening to top your door's threshholds), or by overflow of streams, rivers, and irrigation ditches, or burst pipes in your basement.

There's not much science to controlling this with sandbags. You simply lay the bags end-to-end, overlapping them, packing them tightly, and create a dike that either blocks or "boxes in" the area you're trying to protect. With filled bags each averaging about 16" long and 3 - 4" high, you can secure a doorway (or a basement window) with as few as three to six bags laid horizontally.

If feasible, you might want to consider boxing in the doorway, rather than simply stacking the bags flush against the door. This allows you to open the door, to control the seepage, and gives you another line of defense (if necessary, you can add bags "inside" the box for reinforcement).

If the water continues to rise, you can add layers ("courses") on top of your base. You'll want to tamp the bags as much as possible (if you don't have a tamper, you can use whatever's at hand to hammer them, or at the very least stomp on them).

There'll be seepage from around, under & between the bags. If the water is still (not moving, except "up"), you can minimize this seepage by supplementing with some heavy plastic sheeting or tarps. Putting the sheeting between the water and the bags will allow the pressure of the water against the bags to create some sealing, but it'll be exposed & subject to tearing. Putting the plastic or tarps between the bags and the house is a better idea (click below to enlarge).

You won't entirely stop the water, but you'll certainly minimize it. The water that makes it past the bags can usually be easily controlled. If you find yourself with a lot of standing water - more than a mop or a sponge can handle - an inexpensive pump & 10 - 20 feet or so of vinyl tubing to discharge the water can move a great deal of water in a short time. We can provide these.

If you simply stack the bags flush against the threshold, then your best bet is to seal the door with duct tape (sides & bottom), Then tape some sheeting about a foot or two up the

door, leaving a couple of feet on the ground. Lay your bags on the plastic, then take the leading (top) edge of the plastic & pull it up and over, tucking the free end between the bags and the door. Finally, give the bags a good kick or two up against the door.

The advantage of stacking sandbags directly against a door is that you need fewer bags, and the seal (depending on how good a job you did) is almost bomb-proof. The disadvantage is that you can't open the door until the water goes away, and you don't have a fall-back position. If possible, we advise the "box" as described above.

No sandbags? You can do the same with plastic sheeting (as above) and cinder blocks.

Sheeting & Hillside Runoff

Urban areas

In urban settings, heavy rains or broken pipes & hydrants can cause large volumes of water to move across impermeable surfaces (paved streets, parking lots, etc.) and rapidly overwhelm storm drain capacity - resulting in traffic hazards and putting curbside residences and businesses at risk of water encroachment. Sandbags can be quickly deployed to direct water, or to create a temporary holding embayment that will slow the runoff down & allow storm drains to keep up with the flow until the pumps arrive.

Rural areas

In rural & undeveloped areas, sheeting & runoff from hillsides can be a huge problem - especially with the wildfires that have been plaguing the West the last few summers. Normally, well-rooted vegetation mitigates the water flow on hillsides, and soil absorbs a great amount of water before it enters the streams or rivers in the canyons and arroyos below.

After a fire, however, the undergrowth is gone, and the heat of the fire often bakes the clay-rich soil into a hard glaze ("burn scar") that prevents absorption of rainfall. What would ordinarily be a modest rainfall can sheet into waterways, causing them to overflow their banks. These strong currents often carry large sediment loads and destructive debris - including boulders - which can subvert and overwhelm your sandbag defenses.

The best strategy to control hillside sheeting is to plan well ahead, before the rain starts, with the objective of diverting the water (or at least dissipating its energy). Sandbags can be used to create check dams in gullies, washes, and arroyos, creating artificial "holding ponds" to contain the flow, or to channel off the water off-site.

If topological features exist like natural hollows, rockpits, or quarries, sandbags can be strategically placed to channel the runoff to these & essentially convert them to detention basins. If they don't exist, they can sometimes be created with earth moving equipment (the displaced soil can then be used to make earthen berms to divert & contain the water).

When hillsides are steep and slick, be aware that the pressure of the water can cause the sandbags to slide; you'll want to trench and use whatever natural features (dips, rocks, etc.) to ensure that your line of sandbags doesn't shift. You may want to stagger the bags to stabilize them and to prevent movement or shifting.

Once there's a breach in your line of bags, the weight & pressure of the contained water will start to wash them out, and create a powerful surge that will be near impossible to regain control over. Anything you can do to reinforce your bags - rope, tie wire, netting, pallets or boards, etc. - will help.

This can happen suddenly and is where people can get killed. Once something like this happens, the best thing you can do is to quickly retreat to your second line of defense, where you'll either already have bags stacked in place or - at the least - you'll have bags filled & ready to stack. If possible, have a third line of defense to fall back on as well.

Finally, know your evacuation route in case things get totally out of hand & you have to make a run for it.

Plan for the worst, hope for the best.

High-Flow Surges

Preventing damage from huge surges (ocean surf, torrents rushing down ravines, breaches in dikes, etc.) requires both weight & mass. When loose sandbags are at risk of simply being washed away, they can be useful if they are secured together. Options might include "burritos" (wrapping several filled sandbags with cyclone fencing - see our Erosion page) or filling FIBC bags with sandbags. If you have more time to plan & implement, You may also want also to look into gabions (steel cages made with fence material & filled with boulders).

Since the damage that can be caused by fast-moving water coming off hillsides & down ravines is often compounded by heavy sediment flow & debris (and even tumbling boulders), you're better off trying to control it with rigid structures. Trying to contain it with sandbags may or may not work, but sandbags are inexpensive, low-tech, readily filled & put into place, and don't require anything other than manpower.

If bags are being placed along a river or creek bank, they'll be subjected to strong lateral pressure. They should be laid in a minimum of three wide, and then built up in "stairstep" or

"pyramid" formation (at a minimum, three wide on the bottom, then two wide on the second layer, then topped with a single bag on top).

The rule of thumb in pyramid building is that the width of the base should always be at least twice & preferably three times the height. If the water rises and you need to build higher, you should broaden the base at the same time.

Your foundation should be laid so it won't move or shift (preferably not on slick mud). Trenching, then laying the bags will help secure them.

It's important to fold the openings under the bags (preferably on the down stream side) - you don't want the bag's fill material washing out. It's equally important when laying the bags to overlap them, butt them together tightly, and minimize the spaces between them - if there's a significant flow of water coming from between or under the sandbags, it can undermine the stack & wash the bags out.

Sandbags along the banks of waterways are the first defense. Buildings and houses can be separately protected with long rows of bags placed along their lengths to channel the surging water.

Wells need special attention to prevent contamination by flood waters. They should be protected by a ring (or box) of sandbags, several feet high (see below).

The above photo is actually of a sand boil, which in some cases can appear hundreds of feet from a river bank or levee and undermine your working & staging area.

The same treatment seen here - building a ring or box of sandbags - can be applied to protecting water wells, junction boxes, generators, and other high-value assets.

In high-flow conditions, the power of the water and the debris (rocks, branches, etc) can dislodge your sandbag constructions & wash them away in seconds. You need to use weight, triangular stacking, and whatever kinds of anchors (metal stakes, cyclone fencing, etc) to strengthen your bags.

If possible, have made-up sandbags nearby so that you can quickly repair whatever breaches occur. One large pile of bags strategically located can service several sites.

In all cases, your best strategy is simply to stop the flow, if you can. Second best is to divert it, since it'll probably just keep coming (and it needs to go somewhere!). Third is to try to contain it where it'll do no harm. And remember that if it's surging, it's not going to just be water you're dealing with; it may contain rocks, debris, and a sediment load which will increase its weight & its destructive force.

What might start out looking like just a few inches or a foot of water can rise in minutes to a level where you lose your options and evacuation is no longer possible. Consider what just one inch (1") of rain equals:

Area	Gallons of water	cubic feet of water	Weight of water (1 gal - 8.33 lbs)
30 x 40 roof	748 gallons	100	6,231 lbs (over 3 tons)
100' x 100' sq ft	6,234 gallons	833	nearly 26 tons
1 acre	27,154 gallons	3,630	113 tons
1 square mile	over 17 million	over 2 million	over 72,000 tons
5 square miles	nearly 87 million	over 11.5 million	over 360,000 tons

Be smart, stay aware of what's happening in your area, use good judgement, and - most importantly - know when to back out and cut your losses.

Additional links: Corps of Engineers pamphlet on sandbag use (PDF)

Sandbags can sometimes be acquired from your local fire station or emergency response authorities - but they may be limited in number. Some people have told us - here in Albuquerque at least - that there's a limit of anywhere from 10 to 20 bags per household.

For farmers & ranchers, business, government & tribal agencies, and anyone else, we can provide bags in any quantity, from one to 100,000 (larger quantities need to be pre-ordered). We don't stop at just selling them to you - if necessary, we'll do whatever we can to get your bags to where you need them, give you on-site advice to get you going, and free you up to worry about other things.

Visit our store or contact us directly for prices & options.

Use this information at your own risk. No one associated with New Mexico Dirtbags will have liability for any loss, damage or injury resulting from the use of any information, recommendations, or claims found on this or any other page at this site. All information, advice, suggestions and recommendations are offered in "good faith". Likewise, New Mexico Dirtbags, its principals and its employees, will in no way be held liable for any loss, damage, or injury arising from the use of any of the products sold or provided. Purchasers and users of products, information, and advice made available by New Mexico Dirtbags are hereby notified that they are responsible for conducting their own research, for taking all reasonable precautions, and for assuming full responsibility. It's ultimately all on you.