Friday, 1 January 2016

Flooding in Louisiana: Practical Solutions

The news continues to build about the risk of flooding in the great State of Louisiana.  The Governor of that State has issued a proclamation that
the National Weather Service has issued a flood warning along the length of the Mississippi River with predicted river crests well above flood stage in many locations which, combined with recent weather conditions across the middle of the nation, create the potential for major flooding along the Mississippi River; [as a result of which] ... a state of emergency is hereby declared to exist statewide as a result of the flooding caused by this event, extending along the length of the Mississippi River, Red River and in other bodies of water throughout the State, and the effects of which continue to threaten the lives and property of the citizens of the State
In relation to other states, the American Red Cross has said that
People living near the Mississippi River in Mississippi are being evacuated and Red Cross caseworkers are working with the affected families to provide help as needed. Flooding is also occurring in Illinois, along with severe winter weather in the northern part of the state. Red Cross workers opened shelters and warming centers to help those impacted and feeding people in the shelters and delivering meals throughout several affected areas. 

I've previously written about flood preparedness.  I felt that a little more could be said.  I've prepared this note based on the text Storm and Water Damage Operations (3rd ed., Emergency Management Australia, Canberra, 2007).  This text is used in training (among others) members of the Victoria State Emergency Service.


One of the most heartbreaking parts of flooding is the damage to homes and businesses, and to their contents.  The situation can be made much worse if drainage for the water is inadequate or defective (for example, drains clogged with rubbish).  However, there are means of responding to the risk.



Sometimes the simplest solutions are the best.  If possible, move the contents of a room to the safest place in it (for example, putting furniture or books onto a high table rather than having them at ground level).  If the table or benchtop has a finish on it, consider putting a towel or rug on it first to avoid scratching.  When everything that can be put in a high place has been moved, cover them with a waterproof plastic sheet or a tarpaulin.  Items should be covered at the top and sides.  If you need to use more than one sheet, build the layers from the bottom up so that water will drain downwards and off the pile.

Take steps to keep drains clear of debris.  Ideally drains can be covered by a purpose made wire mesh guard, although other mechanisms might be improvised (for example, netting.  Debris will tend to build up around the guards, however, so it would be prudent to check regularly that the guards are free of blockages.


Water can be diverted out of or away from a building using a makeshift gutter.  You can make this by folding a tarpaulin to half its width, and then folding or rolling the edges to create the sides of the gutter.  Seen in end on, the gutter should resemble this -


If necessary, several of these gutters can be overlapped to drain water over a significant distance (remember to overlap the ends of the folded tarpaulins so that water drains from one to the other, and not out onto the floor).


Sandbags are an excellent way of diverting water and protecting property, but they carry limitations.  Preparing them is slow and labour-intensive.  Laying them requires a degree of skill, and they tend to be heavy to handle (properly filled and dry, about 40 pounds or 18 kilograms each; heavier when wet).

If building a levee with sandbags, consider digging a small trench to provide the base with extra stability.  Alternatively, place the base against a fixed object like a ditch or roadbed.  A levee should be built with slightly inclined sides (that is, from the side it will look roughly like an isoceles triangle).  A levee built straight up-and-down will lack strength.  The bags should be laid in alternating layers.  The first layer must have the bags' short edge against the water, and the second layer the long edge against the water.  The edges them alternate to the maximum recommended height of about 5 feet or 1.5 metres.

Image from here
Alert readers will notice that this diagram is
slightly different from the description I have
given, particularly as to alignment of
sandbags.  However, it generally describes
the intended design.

Waterproofing can be added by threading plastic sheeting through the layers of sandbags

Removing Water

As said before, simple methods are often the best.  Small amounts of water can be pushed out of a building with brooms and squeeges.  Water can also be baled or siphoned (although do not suck floodwater through a hose with your mouth to commence the siphoning process: the water is likely to be contaminated).  If desperate you may also consider drilling small holes in floorboards or levering a floorboard up and propping it open to allow water to drain.


A number of options are available if you have decided to acquire a pump to remove floodwater.  The most common types used for this purpose are "positive displacement" and "centrifugal" pumps.  There are various subtypes, with different strengths and weaknesses.  You should seek advice from a suitable dealer or other person as to what will work best in your home or business.

When using a pump, install a strainer in the suction hose to avoid debris bring sucked into the pump and bringing it to a standstill.  The strainer should be checked for blockages from time to time.  The suction hose should be pointed upstream, into the oncoming water, to operate most efficiently.  Efficiency will also be improved if this hose is as possible, so that the pump is not required to work harder than necessary to draw the water.  Secure the suction hose with a line (or at least a marker, for example a fishing buoy) to help you recover it later.  Avoid sharp bends in the suction and disharge hoses as these will make pumping inefficient or stop it altogether.

Be very careful if using a gasoline-powered pump.  Carbon monoxide buildup in enclosed spaces is extremely dangerous and can be fatal.

Donations (no, not to me!)

Many readers will already be very aware of the flooding affecting or threatening a number of American states at the moment.  To support relief activities, consider making a donation to the American Red Cross.

Image from here

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