Apply for Land Drainage Consent

The discharge of surface water from an impermeable area requires consent in accordance with Byelaw 3. The Board will determine applications received seeking to discharge surface water in accordance with the policy below.

Applications for consent to discharge surface water run-off into any watercourse within the Board’s Internal Drainage District will be considered against the capacity of the receiving watercourse to accept the proposed surface water flows (rate and volume). To assist in determining the application, the Board may require the applicant to undertake hydraulic modelling work.

The requirement for consent to discharge surface water may be waived in writing at the officer’s discretion where the impermeable area is less than 50m2 and is an extension of an existing impermeable area with a satisfactory surface water outfall.

Policy: Discharge of Surface Water

The Board will only approve an application to discharge surface water where the watercourse can be evidenced as being connected to the wider watercourse network.

For systems serving impermeable areas greater than 0.25ha the proposed discharge rate should be no higher than 2/l/s/ha or annual average flood flow rate (QBar or QMed), whichever is higher. Exceptions may be allowable when it is evidenced that to achieve this rate would require a static flow control device (vortex flow control or fixed orifice plate) with an orifice smaller than 50mm* in diameter (or 100mm where debris control is not possible). Systems with a static flow control devices with an orifice smaller than 100mm in diameter should be designed to prevent debris entering the flow control device.

Applications may be refused if the Board’s Officers consider that the proposals may increase flood risk, cause environmental harm which cannot be mitigated, negatively impact the efficiency of local drainage or if the receiving watercourse will not be capable of accepting the planned additional flows.

If consent is granted by the Board, this may be conditional, including the payment of a Surface Water Development Contribution as outlined by the Board’s Development Control Charges and Fees Policy.

Notably it is the Board’s preference that systems are adopted by statutory authorities / bodies whenever possible.

*75mm for the Pevensey and Cuckmere WLMB

The discharge of treated foul water (via an appropriate treatment plant) requires consent in accordance with Byelaw 3. The Board will determine applications received seeking to discharge treated foul water in accordance with the policy below.

The Board’s consent does not replace the applicant’s obligation to seek an Environment Permit from the Environment Agency for the treatment plant and outfall or meet the general binding rules published by DEFRA.

Policy: Discharge of Treated Foul Water

The Board will only approve an application to discharge treated foul water where the watercourse can be evidenced as being connected to the wider watercourse network.

Applications may be refused if the Board’s Officers consider that the proposals may increase flood risk, cause environment harm which cannot be mitigated, negatively impact the efficiency of local drainage or if the receiving watercourse will not be capable of accepting the planned additional flows.

Where the discharge is to an open watercourse, the discharge pipe should be installed through a pre-cast concrete outfall unit dug in flush with the drain batter. Suitable erosion protection should be installed below the headwall down to the toe of the watercourse and also dug in flush with the drain batter.

Where the discharge is to a piped watercourse, the discharge pipe should be connected into an existing inspection chamber, or a new inspection chamber should be constructed to the Board’s specification to accommodate the outfall.

If consent is granted by the Board, this may be conditional.

The alteration of an ordinary watercourse requires consent in accordance Section 23 of the Land Drainage Act 1991, and Byelaws 4, 6 and 15. The Board will determine applications received seeking to alter a watercourse in accordance with the policy below.

Section 23 of the Land Drainage Act prohibits the installation or alteration of a culvert, the installation of a mill, dam, weir or similar obstruction to flow without the prior consent of the Board. Byelaw 4 further restricts the reconstruction, reduction, repair and removal of these structures, as well as the operation or alteration of bridges, headwalls and water control structures.

Furthermore, Byelaw 6 restricts the stopping up or diversion or alteration of flow / water level of a watercourse and Byelaw 15 restricts the dredging or raising of any material from the bed or bank of an arterial watercourse.

As part of any application to alter a watercourse the applicant has the responsibility to prove that the proposed works would not increase flood risk or negatively impact the efficiency of local drainage.

Policy: Watercourse Alterations

The Board will only approve an application to culvert or infill a watercourse if;

• There is no reasonably practicable alternative (including health and safety considerations).
• The proposal is for a replacement culvert or bridge.
• Any culverting is for the sole purpose of providing access (and the total length is the minimum required for the access).
• The proposal forms part of a drainage, agricultural or environmental improvement scheme.

Applications for the installation or alteration of mills, dams, weirs, flow controls, headwalls, bridges and other structures regulated by Section 23 of the Land Drainage Act 1991, and Byelaws 4/6/15 will be considered on a case by case basis.

Applications may be refused if the Board’s Officers consider that the proposals will increase flood risk or negatively impact the efficiency of local drainage, cause environmental harm that cannot be mitigated or negatively impact the ability of the Board to carry out its operations.

Consent is required for all works within 9* metres of the edge of arterial drainage and flood risk management infrastructure (arterial watercourses and water management structures such as pumping stations) in accordance with Byelaw 10**. The Board will determine applications received seeking to undertake works near arterial drainage infrastructure in accordance with the policy below.

Maps on the Board’s webpages clearly show which watercourses are designated as Arterial Watercourses. The 9* metre distance is measured from the edge of the drain (whether open or piped). In the case of an embanked drain this is 9* metres from the landward toe of the embankment.

Although all cases will be considered on a case by case basis, the following points represents common works and their likely acceptable distance. This list is for guidance only:

• Permanent Structures = 9m* from brink (Open Watercourse) / 9m* from outside edge (Culverted Watercourse)
• Trees = 9m* from brink (Open Watercourse) / 9m* from outside edge (Culverted Watercourse)
• Ground Surfacing = 7m* from brink (Open Watercourse) / 1m* from outside edge (Culverted Watercourse)
• Demountable Fencing = 7m* from brink (Open Watercourse) / 1m* from outside edge (Culverted Watercourse)
• Demountable Structures = 7m* from brink (Open Watercourse) / 3m* from outside edge (Culverted Watercourse)
• Hedging = 7m* from brink (Open Watercourse) / 3m* from outside edge (Culverted Watercourse)

*7 metres within the Waveney, Lower Yare and Lothingland IDD

** Byelaws 10 and 17 for Waveney, Lower Yare and Lothingland IDB

Policy: Works within 9* metres of Arterial Drainage Infrastructure

The Board will only approve applications for consent for works (including replacement works) within 9* metres of arterial drainage infrastructure (as required by Byelaw 10**) if the Board’s officers consider that the proposed works will not increase flood risk, negatively impact on the ability of the Board to carry out its operations (including but not limited to the Board’s usual way of working, current access arrangements, available resources and the risks posed to Board employees, now or in the future) or increase the liabilities of the Board. Permanent Structures (any building which is not demountable, including any extension to a previous structure) are unlikely to be approved within 9* metres of the brink of any arterial drainage infrastructure.