The World According to Tarp

With rainfall that felt like it should be measured in metres (not centimetres), we were glad that we brought a plethora of tarps with us. These included the MOTHER of all tarps. I kid you not, I think the dimensions were 32x20 feet! Plus, we attached another 12x24 foot one to that to cover a fire pit.
One thing that few of us had considered before this weekend when it came to tarp setup, was drainage. Sure, you put up a tarp to keep water off your table/tent/firepit... but where does that water go once it's on the tarp? Usually, with a light rain, or even a brief downpour, most of the rain gets caught in the sags in the tarp, or spills down the sides and is absorbed into the ground, but with a steady, heavy rain the ground quickly becomes saturated and water begins to pool... and even worse... to flow.
The Highs and the Lows
One of the first things we like to do when we show up at a site and there's a good chance of rain at any point in our stay, is to set up the tarp before anything else is up. Your first consideration is how much rope you have and where good supporting trees are located, but if you're expecting really foul weather, also keep in mind where the high and low points of your site are. You'll want drainage points on your tarp to be uphill from the low points on your site so water flows away from your 'dry area'. If you can't position your ropes to do that, you can use string tied to water bottles or saplings to pull the tarp edge down by the grommets. This will force the water to flow to the low point of the tarp. You may have to use long sticks as tent poles to hold up sags in the tarp, but we found this worked really well.
Into the Trenches
So... your tarp is up and the water is flowing, but it's flowing into your dry area and pooling up. Now what? Well, you change the flow of water by digging yourself a little trench. It doesn't have to be spectacular and deep. You can even use a heavy stick. Just draw a line in the ground that either leads downhill through your dry area or out of the dry area from where you've already got pooling. The only things to keep in mind is that you want the trench to lead somewhere downhill from where your dry area is, and that you want your trench to get steadily deeper to ensure that the water will keep flowing. Like the canals of yesteryear, you'll want to dredge these trenches from time to time to keep the flow going. Just drag a stick along with the current to push silt along. It also helps to clear downgrades of debris like leaves and sticks that can impede water flow away from your dry area.
"I'm Dutch... Isn't that weird?"
Your last resort is to go Dutch and start building dikes (no, not those ones). Now, it's harder to stop flowing water than it is to redirect it, so this is what you do AFTER trenching hasn't quite done the trick.
Mud and dirt will quickly dissolve with water and just add to the mess, so you your best bet is to jog into the bush and round up a whole lot of forest-floor organic matter. If it's already raining (which I think it will be, since you're in a last ditch effort to bail out your camp) then this stuff will already be good and damp, and that means it'll be good and heavy and easy to pack into shape. Just dig it all up (a frying pan is good when a shovel isn't handy) and pack it just inside your tarp-line or downhill from your flooding area. A triangle shape works well, especially once you pack it a bit with your feet to seal it up. Even if this stuff takes on some water, it just makes the matter that much denser and helps stop water that much more.
More to come tomorrow.