Half Marathon Nutrition

Ok, I didn't run a Half Marathon on Saturday, but I did run a 20k (12.4 miles).  The problem I ran into was at about Mile 10 or so, it was like my legs didn't want to move.  I've been trying to figure out what happened.  Was I starting to dehydrate?  Did I bonk?  Did the heat of the day got to me since we lost our cooling breeze?

My pre-race routine was pretty much the same for all my races, I ate two packets of oatmeal when I got up, drank about 16oz of Sports Drink and drove to the race.  The temp was low 60's at the start and I was drinking about half a cup of water at each stop, which happened to be about every mile.  I started drinking a full cup at about mile 6 and dumping 1 to cool off a bit.  At about Mile 9 is when it seemed to get real hot, I would guess the temp was only in the low 70's by then, but we started running with the breeze.  Not much of a cooling effect when running with the breeze.  According to my Garmin I burned just shy of 2000 calories, now of course we all think these things over estimate a bit, though it is a bit higher than any training runs, which of course it should be as I was running at a faster pace.

Ok, here are the facts, my training logs and race report are posted:

http://www.beginnertriathlete.com/discussion/training/index-weekly.asp?memberid=15677&year=&month=&day=

http://www.beginnertriathlete.com/discussion/forums/thread-view.asp?tid=172656

as is the course (two big hills but rest fairly flat to small rollers)

http://www.beginnertriathlete.com/discussion/training/map.asp?routeid=102676

Ok, so here's my question:

Would you chalk this up to over heating and too little water intake or would you think that you need to add some Gells or other nutrition for a Half Marathon?  The Half Marathon is on Sept. 13, the weather could be cool, it could be hot, won't really know until we get closer to race day.

My thought was, and I figured I would practice this a bit, to increase my water intake at the start, perhaps a full cup.  Generally on training runs I'll drink about 16oz of water in an hour and a half.  I could drink more but it's hard to carry much more than that.  I was also thinking about doing a gel about 10-15 minutes before the start and then about 30-40 minutes in and at about 60-70 minutes in.  Sport Beans would work as well, though I think they are a bit more difficult to consume while running.

Ok, I'm looking for any other advise or perhaps a just, you're on the right track to make sure I'm not forgetting something.