Intermitting hazard after a rainy day?

After a heavy rain my hazard lights turn on and the hazard switch became inoperative. Also my boot will open with the back doors. This is an intermitted fault and there is no time when it decides to repeat the action. However I have notice that the channel under the bonnet and under the wipers was filled with water due to a blockage in the water escape path. Also I have notice a lot of water on the passenger side ( front ) Someone had told me that most probable the BSI unit seems to be the problem. Please help