Blackwater & Colne
The Blackwater and Colne Estuaries are situated on the coast of Essex, between Colchester to the north, Dengie to the south, Maldon to the west and Jaywick at Clacton-on-Sea to the east. Human changes to the estuarine complex have resulted in the combination of the Blackwater and Colne Estuaries into a single system that flows into the sea. As a result the estuary channel is heavily constrained and at risk of flooding. Any future development of flood defences within the estuary should enhance the natural estuary development, where possible.

The Blackwater and Colne Estuaries converge to the south of Mersea Island , between Sales Point and Colne Point, prior to discharge into the North Sea . The Colne extends for approximately 14km before reaching its tidal limit at the Colne Barrier, which is located on the downstream side of Wivenhoe. The Colne Barrier was constructed to improve tidal defence of the riverside residential, commercial and industrial areas of Colchester whilst providing a new defence for Wivenhoe and Rowhedge, which used to be at risk of flooding. The Blackwater extends for approximately 20km before reaching its tidal limit south of Langford near Maldon, with numerous tributary creeks along its length.

The estuary complex consists of relatively deep, narrow channels with limited intertidal margins. This is due to the reclamation of intertidal areas. The estuary suffers from poor 'flushing' on the low ebb tides resulting in the deposition of sediment and a decrease in channel depth. The flood embankments make this problem worse, as they further constrain the estuary processes. As tidal velocities increase erosion becomes a dominant feature of the estuary channel, placing stress on existing flood defences.

The condition of the existing flood defences range from 'very poor' to 'good'. However, estuarine processes and the rising sea-levels are placing added pressure on the defences. Given the wealth of assets within the estuary flood plain, the need for flood defence management is imperative. The Blackwater and Colne Estuary Flood Management Strategy will identify the most appropriate way of managing flood defences within this estuary complex. Given the historic impacts of human activity in this area, future flood management must progress in a sustainable manner.

Assets at Risk
Within the 11,468ha of coastal floodplain (defined as being land below the 6.5mAOD contour) surrounding the Blackwater and Colne Estuaries, there are a significant number of assets at risk of flood damage, including over 11,500 properties, 9,031ha of moderate to high-grade agricultural land and 154km of flood defences.

There are many properties spread across the flood plain in numerous sparse settlements, villages and in the principal towns of Brightlingsea, Colchester, Maldon and West Mersea . The Ministry of Defence owns a significant portion of the land and assets at risk within the Fingringhoe and Langenhoe Ranges .