We are extending a large paver patio in our back yard with a 10% grade from the existing patio towards the back of the yard. We have already dug out 7" of dirt, dumped gravel and leveled it. We are now in the process of dumping gravel screening and laying the brick pavers. As this is a large area it will take several days to complete. We started yesterday and got a good chunk done but we had heavy rains last night which washed out sand from under the old pavers and some screening from the new pavers causing the first few rows to sink. Knowing it was going to rain we covered the area well with plastic sheeting weighted down with bricks. However all the rain drains down towards our working area and our preventative steps made little difference. We had to redo several rows of pavers this morning. We are expecting heavy rains the next few nights with some flash flood warnings. How can we prevent the water from washing away our hard work over the next few nights?