The Stour Estuary, parting Essex to the south from Suffolk to the north, extends nine miles from Manningtree to its mouth on the North Sea at Harwich. It is the final, tidal channel of the River Stour, up to a mile in breadth, in the form of a drowned valley.
The Stour is tidal as far up as Flatford, but opens up into a sea channel, the estuary, above Manningtree, and soon is navigable even at low tide, when most of the width of the estuary is tidal mudflats.
The Port of Harwich is on the lowest reach of the estuary, by which time even at low water the waters fill most of the channel. Here the estuary is joined by that of the River Orwell and the two open into the open sea.
The mudflats in the upper estuary are rich with wders and other waterfowl, which attracted the Royal Society for the Protection of Birds to create a reserve here.
RSPB Stour Estuary
The reserve is unusual in that it consists of two divergent habitat types: mudflats of the foreshore (fringed by saltmarsh and estuarine reeds), and 130 acres of deciduous woodland, mainly oak and coppiced sweet chestnut.
The estuary is important as a breeding, roosting and wintering site for many waterfowl and other birds, including woodpeckers, nightingale, blackcap, whitethroat, sedge warbler, reed warbler, wigeon, common shelduck, northern pintail, common teal, dark-bellied brant goose, grey plover, common redshank, curlew, dunlin and black-tailed godwit.
Mammals to be seen include red fox Vulpes vulpes, badger Meles meles, grey squirrel Sciurus carolinensis, and hazel dormouse Muscardinus avellanarius.
Butterflies and rare moths include white admiral Limenitis camilla, chocolate-tip moth Clostera curtula and peach blossom moth Thyatira batis.
The Stour estuary is the focus of a children's novel by Arthur Ransome, Secret Water (1939).
- Location map: 51°56’7"N, 1°11’10"E