The forerunners of today’s Internal Drainage Boards date back to the time of Henry III who established a Commission for drainage of Romney Marsh in Kent in 1252. Most IDB’s today were established by the Government following the passing of the Land Drainage Act 1930.

The Lower Medway Internal Drainage Board was set up in 1934 following a public inquiry held by the Minister of Agriculture and Fisheries because there had been several appeals against the proposed inclusion of certain areas in the initial Internal Drainage Districts. As a result of that inquiry the Minster set out various principles incorporated in what became known throughout the country as the “Medway Letter”.

Areas of benefit were defined as those areas included in a contour line 8 ft above highest known flood level in non-tidal areas and 5 ft above high tide in coastal areas. These became the Upper (non – tidal) and Lower Medway Internal Drainage Districts.

The Lower Medway Internal Drainage Board area is quite different and consists of land that would have flooded by sea water but for the construction of earth embankments or sea walls. As mentioned in the “Medway Letter” the drainage district is based on the 5 ft above high tide contour.


Because the areas that were once tidal are not continuous along the coat, the Internal Drainage District tends to be fragmented with pockets of lowlands either side of the River Medway.

The North Kent Marshes IDB was created in August 2016 and was known previously as the East of Gravesend Internal Drainage District and Board since circa 17th Century. The East of Gravesend IDB was priorly administered by the Environment Agency until its dissolution and reconstitution as a locally represented IDB. The Board was administered by Medway Council until 2021, and is now administered alongside the Lower Medway IDB.

Both Boards obtain funds to carry out the necessary maintenance by levying drainage rates on the owners and occupiers of land within the Drainage Districts. Agricultural land is levied directly to the landowners or occupiers, businesses and domestic properties are also levied but collected on behalf of the Board by the relevant local authorities as part of the local council taxation and paid to the Board as a Special Levy payment.