Matthew, I did not say there was peak 8,500 years ago, but that the delta regions flooded 10,500 years ago, or 8,500 BC. Your graphs show a 120 meter rise in the level of the oceans, starting to accelerate15,000 years ago and ending 7,000 years ago. Yes, the flood could be placed anywhere in the is range, but never younger than 6,000 years ago. It is not the slow rise of the ocean that was deadly, but the flash flooding coming from the irregular release of water from the melting glaciers. Australia did not experience the dangers that the near east did in this respect. As the ice receded in Eurasia, the dearly regions were deadly.
The reference for the 8,500 BC number comes from the work of Heinz Blum. (“Erwaermung bewirkte die Sintflut.” Museion 2000,3/1994, 40-46. Print) This is based on many factors, including the oldest bricks found in the near east have been dated at 8,300 BC - the first signs of constructed civilization.