We've all hear the old saying: "An ounce of prevention is worth a pound of cure." I question the cost- benefit ratio on that adage occasionally. Today's is an easy one.
Our home is downstream of a wildfire that is now more than 90,000 acres large and less than 50% contained. The nearest burned perimeter is about 10 miles away and includes terrain that is up to 5,000 feet higher in elevation. Weather patterns are setting up to start the summer monsoon rains within the next 10 days. There is a reasonable potential for black muck and goo to make it to our little town. It is also reasonably possible for a frog-strangler to bring some of that nastiness as a good-sized flood.
In 1999, we had a flood from about a .75 inch rain that flowed about 20 inches deep through our yard. It was the first flood of any significance since 1972 (long story, very high water, dead people). The 1999 20 inches was about 3 inches below the threshold into our house. Since then, we have built a 2 foot wall on the upstream side of our property but outside the chain-link fence and built up the driveway outside the gate by about a foot. Unfortunately, that leaves a 10-foot wide driveway 18 inches below the wings of the wall where flood waters and goo can come in. The plan was to insert boards so that they are between the stone wall and the chain-link fence and would be held in place by the pressure of any small floods. Oops, we forgot. The boards were on-hand, but have since been used for something else (they were really nice 2 X 12's that someone gave us).
We have flood insurance, but that only helps recover from a horrid mess. The experts describe the source drainage area as a "50,000 acre Walmart parking lot covered with feet of ash and rock poised at a 45 degree angle above the town." I believe we need a little more protection, but not at great expense. So here's my solution, which cost me under $20 at Home Depot.
The 2 foot piece of rebar will be used in conjunction with the U-bolts and the nipple (lower left of pic) to make a stop for the wide gate. In the 1999 flood, the long lever-arm of the wide gate made it vulnerable to popping open. Someone drove down the street through a foot of water and the wake popped the gate open. We went from a trickle to a real flood in our yard in about 30 seconds. So how will this work? Using a small auger on my drill (and possibly a pick) the 6 inch nipple goes vertically into the ground to hold the rebar. The rebar will pass through the 3 U-bolts attached to the chain link and into the nipple to strengthen the closure of the gate. This assembly will be about mid-way on the gate. The physics would move it closer to the opening, but if I do it wrong, we could puncture a tire as we drive in. That will significantly raise the cost of an ounce of prevention.
This gate-closure strengthening will work in tandem with the next part, using the 2 lag bolts and the 4 larger U-bolts (to the right of the rebar in the photo) . I have 2 large scraps of 5/8 inch exterior grade plywood. Neither is large enough to cover the opening but if I drill matching holes and bolt them together with a small overlap, the two will cover the opening to about 3 feet of depth. Step 2 is to drill smaller holes in the corners of the new, larger plywood to accommodate the U-bolts. I'll attach the U-bolts to the fencing (at least one side to a fence post, as they are anchored with concrete) outside the gate, so the weight will not compound the gate problem. Because of the hydrologic dynamics of the location, once some water is slowed or stopped by this, the water will drop sand and gravel and build up the driveway, helping build a larger 'dam' against subsequent flood waters.
It should take me about 90 minutes to do all he work except driving the nipple in the ground. Once the plywood is prepped, it can be kept nearby until needed and then assembled in about 15 minutes. Emplacing the nipple in the hard ground is the wild card, time-wise. I can also put one of those rubber end caps over it so it will be open to receive the rebar when finally needed.
Is this a great permanent solution to future flood? No. This is an ounce of prevention for an abnormally bad but low probability (but certainly possible) post-fire flood response.
The risk is real but low to moderate. The potential damage is high if it happens.
At less than $20 bucks an ounce, I'll take an ounce of prevention, please.