Changes in the mouth of the Ouse

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The Ouse was historically a large estuary similar to the Adur. Much of the land north and east of Newhaven is very low lying, and consists of reclaimed tidal flats. The sea once reached upstream beyond Barcombe some 15km north of the present coast (1) and in Roman times the Ouse exited along the western margin of the valley beneath the chalk cliffs of Castele Hill (2). By Medieval times drifting shingle had deflected the exit eastward to the foot of Seaford Head.
By the sixteenth century the river mouth at Seaford had become so heavily silted that flood waters had difficulty escaping to the sea and so, to reduce the flooding of the Lewes and Laughton Levels, and to facilitate navigation (3), a new outlet was made by cutting through the, shingle at 'new haven', probably in 1539 (4), thus returning the mouth to its position of a millennium before. The condition of the new outlet started to deteriorate soon after the cut, and drifting banks of shingle frequently obstructed t new exit making entry to the harbour difficult throughout the sixteenth and seventeen, centuries (5). At the time of the Armada Survey in 1587 (Fig 5a) the mouth is shown 300-400m east of Castle Hill and a small spit marked as 'beache', diverts the river 200m eastward. The Survey map also shows how the valleys draining into the main Ouse channel were reclaimed for agriculture or salt production. By 1698, Dummer (Fig 5b) indicates that drifting shingle closed the exit at 'Newhaven' and the new exit was 1km to the east at Tide Mills. The river escaped to the sea through a complex maze of channels and many low lying shingle banks. A kilometre to the east of the mouth the old river channel running towards Seaford now formed a lagoon behind the shingle beach. Little was done to alleviate the situation for a long period.
In 1731 the western exit at Newhaven was re-excavated and piers were built to try to stabilise the outlet, but by 1766 shingle had again formed. across the mouth (6). Lt. Roy in 1757 shows the 1731 exit with stabilising piers and a clear picture of the old sixteenth century channel to Seaford. At the date of Yeakell and Gardner's survey (Fig 5c), little had changed: the exit was roughly in the same position, possibly deflected slightly to the east and the lagoon occupying the old channel to Seaford appears to be larger than in 1698.
In 1791 a short breakwater was built to the west of the harbour. The River Ouse was straightened at several points and drainage sewers were constructed (7). The breakwater was improved by a groyne of over 150m in length in 1847 and this was subsequently replaced with a much longer breakwater of 800m in 1890 which survives to the present day (8).
The first edition Ordnance Survey- 6 inch of 1873 shows the confined exit and groynes established in 1847 (Fig 5 d). Stabilising of the river inland is apparent with the construction of the Railway Wharf and the Wharf Station. The lagoon east of Tide Mills has been embanked forming the Mill Pond in the channel feeding Mill Creek. The Salts situated between the river and the pond was a man-made inlet controlled by sluices to the creek and constructed for oyster cultivation until disease curtailed the industry. By the time the third edition 6 inch map was produced in 1911 (Fig 5e) the Mill Pond and the Salts had been drained leaving only a depression tough the Mill Creek remained. As the harbour grew in importance, the river banks were further developed creating the North Quay and East Wharf along with numerous jetties on the west shore. This map edition shows the 1890 breakwater and new East Pier with coarse material beginning to build up along its west side. The latest 1:50000 Landranger Ordnance Survey map surveyed in 1982 shows very little change to the river mouth (Fig 5f). Mill Creek still exists though as a rather dirty and unused backwater since its maintenance ceased after the mill at Tide Mills became redundant. Sediment has continued to build up west of the breakwater forming a vast accumulation of shingle which extends seawards for more than 120m and westwards for more than 500m.
NOTES.
1. Burrin, P.J. 1982: The Coastal Deposits of the Southern Weald. Quaternary Newsletter,- 38, PP 16-24.
2. Brandon, P.F. 1971: The Origin of Newhaven and the Drainage of the Lewes and Laughton Levels.- In Sussex Archeological Collections.- Vol 109 PP 94-106.
3. Ibid. 4. Robinson, D.A. and Williams R,B,G. 1983: The Sussex Coast Past and Present. in Sussex; Environment, Landscape and Society.- The Geographical Editorial Committee. University of Sussex (ed), Alan Sutton, chapter 3 p57.
5. Ibid.
6. Brandon, op. cit.
7. Ibid.
8. Robinson and Williams, op. cit.