Areas of the Hampshire coast between Chichester and Portsmouth seem to have smaller alternating fresh and salt regimes. The river at Emsworth was dammed (in 19C?) above the beach to create big, fresh-water mill-pond originally powering a mill operating when the tide ebbed. (The mill closed long ago and the building is now a yacht-club.)
Parts of Poole Harbour are similarly a mix of fresh-water and salt-water habitats. It is the combined estuary of the Rivers Frome and Piddle, and various smaller streams; and in area forms one of the world's largest natural harbours. I thinkl only Sidney Harbour is larger.
In Weymouth the R. Wey's estuary was dammed in the 1930s, with tidal sluices in the dam.
So the downstream side, open to the sea some distance further on, is salt with some dilution at low tide, but the upstream side stays fresh with reed-beds and freshwater life, and now a bird reserve.
West Bay harbour, on West Dorset, has a similar barrer though the R. Brit's flood-plain is smaller.
