Monument record SUE 087 - Post Medieval or Medieval sea defences in Sudbourne parish

An extensive flood defence bank of Post-Medieval or Medieval date is visible as an earthwork on aerial photographs of 1943 onwards, centred on circa TM45445265 (S1). The bank runs for about 5km along the eastern bank of the river Alde, but also encloses a large area of marshland that separates the river from the coast proper. A more realistic estimate of the actual length of bank, including the sections constructed to enclose Lantern Marshes, would therefore be closer to 10km. Much of the western section of bank is marked on a map by Norden, dated circa 1601 (S2). However, a number of sections appear to have been subject to erosion or damage and have subsequently been repaired or superseded. The western section probably therefore dates to the late Medieval or early Post-Medieval period. The construction of this section of bank also closely follows the parish boundaries as marked on the current Ordnance Survey base map and a historic map of circa 1800 (S3). The sea defences were probably constructed on a parish-by-parish basis, with this section being built by the parish of Sudbourne. Much of the bank on the eastern side of Lantern Marshes is not marked on the map of circa 1800, and can therefore be said to post-date the drawing up of the map. This stretch is marked on the first edition Ordnance Survey map of circa 1884 and its construction can therefore be dated with some confidence to the early-mid 19th century (S4). However this eastern stretch of bank is only visible on the available photographs up to 1955 (S5), after which increased modern military activity results in extensive remodelling of the sea defences in this area (see ORF 021).