Diss is a market town, civil parish and electoral ward in South Norfolk, England; it is near to the boundary with Suffolk. It had population of 7…Diss is a market town, civil parish and electoral ward in South Norfolk, England; it is near to the boundary with Suffolk. It had population of 7,572 in 2011. It lies in the valley of the River Waveney, round a mere covering 6 acres and up to 18 feet deep, although there is another 51 feet of mud.