Illiterate,
I forgot to answer your other question. Food does not spoil in storage yards (or anywhere else).
barryp,
Yes, that's a common sight. Food farm cart pushers will not head for a granary if all of the available space in the granary will be taken by cartloads that are already on the way. However, a farm cart pusher will always head for a storage yard that has space for his crop, so making sure that a storage yard can accept some of each crop will get all cart pushers off the floodplain. (A cart pusher with an industrial crop, such as barley or flax, may head for a workshop instead, but that will still get him off the floodplain.)
Therefore, as you indicated, having a small amount of storage yards space set to "accept" a food, with at least one granary set to "get" the food, will "store" food in the farm cart pushers, so very little space is actually needed in granaries or storage yards. This is a popular technique, but it does have a drawback. If food in the cart pushers barely lasts through the year, so that there's no available space in a storage yard for food at the next harvest, then almost all of the farm cart pushers might perish in the flood, causing stored food to run out soon after. This might not matter, since a fully stocked house has at least a 2 year supply of food (for the current number of residents), but it's something to keep in mind. If you don't mind micromanagement then the problem may be avoided by setting the storage yard to "accept 1/2" of the food at harvest time and then setting it back to "accept 1/4" before the carts arrive. (I use "accepting" storage yards to store food, but generally much more than 1/4 of a yard since I dislike micromanagement.)
[Edit] Must refresh screen before posting. Beaten by VitruviusAIA. (5 minutes!)
[This message has been edited by Brugle (edited 12-27-2002 @ 11:51 PM).]