Saving My ‘Doomed’ House
‘WHY buy a house that everyone knows is doomed’? That seems to have been the view of my neighbors. And I suppose they did find it strange, as the house is perched on a bluff right at the edge of Lake Michigan.
You see, the water in Lake Michigan, as with her “sister” Great Lakes, has been rising for several years. This has resulted in a number of homes being “undermined” by water erosion and their sliding down the bank to their destruction. My new home was considered a prime candidate for just such a plunge.
What do most of the homeowners here do to try to stop the erosion? They begin a ‘war with the waves,’ which is often a very frustrating and expensive battle. The usual defense is a seawall either right at the water’s edge or a few feet out into the water. Some of my neighbors have spent thousands of dollars on these, only to have them demolished by the waves.
Types of Seawall
I had studied the various types of seawall. They are usually made of wood, sheets of steel or steel-reinforced concrete. I soon discovered that each had its disadvantages. A wooden wall is cheaper and easier to install, but eventually will need replacing, as it cannot withstand the violent storms common on the Great Lakes.
To install steel sheeting you need a crane to lift the sheets into position while they are being driven into the sand. Sometimes if the equipment cannot be taken down the bank to the location, it must be brought in on a barge. You can imagine the cost of all of this!
The third type, a solid wall of reinforced concrete, seems the least desirable. The waves pound these to pieces more rapidly than the wood or steel barriers, apparently because the concrete has no “give.” I quickly came to appreciate the tremendous force that a “mere” wave can exert!
A Different Design
Why do waves deposit sand on one shore, actually building beach, and yet claw it away from another? Obviously there are many factors. But by studying the waves I started thinking about the design I eventually used.
As waves splash up on a gentle beach, you can see part of the water sinking into the sand, reducing the amount of water returning over the surface of the beach. Thus, too, each wave deposits some sand, building up the beach. Could some barrier be made to imitate God’s creation, a natural beach? I reasoned that a wall that waves could wash up into and that would slow down the returning water should help actually to build beach.
Further, standing at the edge of Lake Michigan, one can feel the ground “vibrate,” because the waves come in with great force. We cannot abruptly stop such a force, I thought. So I eventually concluded that the design flaw of most seawalls was their angle to the incoming wave. They are generally vertical. The wave is thus required to come to a “dead halt.” It is the old story of the irresistible force soon weakening the not-so-immovable object!
You might think that the solution would be to make a wall so strong that there would be no weak spots. But there is another problem fundamental to a vertical wall.
Sand naturally builds up behind the wall as the waves wash over, carrying sand with them. And as the waves smash against the face of the wall there is a vibration of soil behind the wall causing the soil to settle. This soil will pack tighter and tighter, forcing the wall to lean forward toward the lake.
Once a seawall leans forward you have real trouble. The new angle causes a greater down turbulence of the striking water, which rapidly eats the sand away on the lake side of the wall. Thus, you have more and more pressure behind the wall and less and less support in front. Soon the wall tumbles into the ditch the waves have made in front of it.
With all these drawbacks to a vertical wall, and my observations regarding a natural beach, I concluded that whatever I installed should lean “backward”—toward the bank. The waves would be stopped gradually. Ice and debris could ride up the structure instead of battering against it.
But how could an economical barrier be made that would lean toward the bank and also allow the waves to wash up into it?
Constructing My “Home Saver”
I eventually decided upon a seawall made up of unlinked concrete panels or slabs. If each panel is free standing, one panel can move or give a little without straining others. Of course, the size of such panels would depend on the need, but I made forms to cast a panel about ten inches (25 centimeters) thick, eighteen inches (45 centimeters) wide and eight feet (2.5 meters) long. I reinforced each panel with three steel rods running its length.
Then I used a centrifugal pump that is designed for a high volume of water (about one hundred gallons [380 liters] per minute) to wash a large enough hole in the sand to accommodate a panel. They were set deep with only about eighteen inches (45 centimeters) of the concrete above the sand level. Each panel was tilted shoreward about thirty-five degrees from vertical.
Now something was immediately needed on the shore side of these panels. It had to be heavy enough to withstand continually washing water and yet let water seep through. I found granite stone to be the best because of its great weight for its size. So I removed the sand to a depth of about three and a half feet (about one meter) below the top of the concrete panels and dropped in small stones.
As you can see from the diagram, the technique is to graduate from small stones at the base to larger rocks at the top of the panels. The heavy stones on top are not moved by stormy waters, and the smaller stones beneath prevent spray and heavy rains from washing the soil out through the stone. It is also wise to put a layer of gravel over the sand on up the existing bank.
A Severe Test
Not long after I had completed construction, a violent storm whipped across the Great Lakes. In fact, this storm sank one of the larger ships on the Lakes, the 729-foot (222-meter) Edmund Fitzgerald. All through the tempest I wondered whether my barricade would hold. Afterward, I was delighted to find no serious damage to the entire length of the wall.
Today I have about 150 feet (45 meters) of seawall and, so far, it is working well. I have learned that this approach does build beach as hoped. It is apparently especially effective if the waves come at the shore ‘straight on.’
Whether there will be long-range problems, it is too early, after only two years, to say. But our “dike” has demonstrated its durability and so my family now resides in safety. We no longer live in a doomed house! Contributed.
[Diagram on page 25]
(For fully formatted text, see publication)
REINFORCED PRECAST CONCRETE PANELS
Lake Bottom
18ʺ
Gravel
Granite stone graduating down to 1/4ʺ stones