Good advice so far from RMDAngler. He has some good experience and opinions.
For starters here is my initial input.
1. Your pond looks to be circular. To get a good idea of the true size or area of your pond and if it is one acre it will have a diameter of 236ft and a radius of 118ft. The circumference around the top rim should be 740-750ft(diaXpi). Use 3 foot strides to walk around the top rim and see what you get for a distance.
2. I do not think the patch of cattails surrounding the small pond will be beneficial when it becomes submerged. All this organic matter will decay and create black muck and phosphorus enrichment feeding nuisance algae and weeds. The dead cattail stems will not last long when covered with water. If water covers the cattails less than 4ft deep expect cattails to grow and expand around all the areas of the old pond less than 6 ft deep. I would use a herbicide to kill the cattails before the pond fills. The old pond basin will act as a sunken island but I would not want cattails growing in that region. IMO it will be a constant source of pond management problems later such as constantly seeding more nuisance cattails around the new pond perimeter. Blue and red native water iris, pickerel weed, lizard tail, variegated sweet flag, and several other shoreline plants are a much better shoreline plants than cattails. Cattails grow too deep (6ft), spread too fast, create too much organic fodder, and make the shoreline so you can see through them nor fish over them.
More opinions later.
Last edited by Bill Cody; 10/24/14 11:11 AM.