Hi, I wonder if anyone can help me

I have an old rectangular stone/concrete sided, and clay bottomed spring fed pond in my garden, about 25 by 15 m and around 1 m deep. The pond drains out over a small sluice gate, so the level is kept constant throughout the year. The sides of the pond extend up about 50cm above the level of the water. The previous owner cleared out a load of silt a few years ago, and this is now sitting next to the pond, a pile about a metre high, covering around 30 sq m.

My question is this, how could I build a retaining structure in the pond to hold a portion of this silt so that I could have a bog garden in it. Is this even a halfway sensible idea ?

Thanks