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Surface Water Management Plans (SWMP)

A Surface Water Management Plan (SWMP) is a plan which outlines the preferred surface water management strategy in a given location. In this context surface water flooding describes flooding from sewers, drains, groundwater, and runoff from land, small water courses and ditches that occurs as a result of heavy rainfall.

A SWMP should establish a long-term action plan to manage surface water in an area and should influence future capital investment, drainage maintenance, public engagement and understanding, land-use planning, emergency planning and future developments.

surface water flooding

A surface Water Management plan should be assembled based on the following four phases.

1 - Preparation

2 - Risk Assessment

3 - Options

4 - Implementation & Review

These four phases are elaborated on further below, or if you are starting to realise what a time consuming process this is, then why not give a us a ring and we'll do you surface water management plan for you!

5 - CIRIA C697 or BRE 365


Preparation of a Surface Water Management Plan

The first phase of a SWMP study focuses on preparing and scoping the requirements of the study. Initially, partner s and stakeholders should identify the need to undertake a SWMP study. Once the need for a SWMP study has been identified a partnership should be established, (if one does not already exist), and partners should identify how they will work together to deliver the SWMP study. The aims and objectives of the study should be established, and in parallel the partnership will also decide how they will engage with stakeholders throughout the SWMP study. An assessment should subsequently be undertaken to identify the availability of information. Based on the defined objectives, current knowledge of surface water flooding, and the availability of information, partners should agree the level of assessment at which the SWMP study should start. Recently the new CIRIA Mitigation Indices have started to be enforced.

Risk Assessment for Surface Water Management Plan

The outputs from the preparation phase will identify which level of risk assessment will form the first stage of the SWMP study. The first stage is likely to be the strategic assessment where little is known about the local flood risks. The strategic assessment focuses on identifying areas more vulnerable to surface water flooding for further study. The intermediate assessment, w here required, will identify flood hotspots in the chosen study area, and identify quick win mitigation measures, and scope out any requirements for a detailed assessment. A detailed assessment of surface water flood risk may be required to enhance the understanding of the probability and consequences of surface water flooding and to test potential mitigation measures in high risk locations. Guidance is provided on undertaking modeling to support a detailed assessment of surface water flood risk and mitigation measures. The outputs from the strategic, intermediate and/or detailed assessment should be mapped and communicated to all stakeholders including spatial planners, local resilience forums, and the public.

Options for Surface Water Management

In this phase a range of options is identified, through stakeholder engagement, which seek to alleviate the risk from surface e water flooding in the study area. The options identified should go through a short-listing process to eliminate those that are unfeasible. The remaining options should be developed and tested using a consideration of their relative effectiveness, benefits and costs. The purpose of this assessment is to identify the most appropriate mitigation measures which can be agreed and taken forward to the implementation phase.

Implementation and Review of Surface Water Management Plans

Phase 4 is about preparing an implementation strategy (i.e. an action plan), delivering the agreed actions and monitoring implementation of these actions. The first step is to develop a coordinated delivery program. Once the options have been implemented they should be monitored to assess the outcomes and benefits, and the SWMP should be periodically reviewed and updated, where required.

Exceedance Route Modelling

Water if add to a slope will flow. But how deep and how fast? This is what we aim to establish when we car out exceedance route modeling. In events up to (say) 1:100 year the SUDs system will contain surface water on site, whilst releasing it at a given rate.

However when the SUDs system is past its maximum capacity water will pond . . .or flow across the the sites surface. Where will this water go? What will it do?

Flow Control

In order to make best use of the attenuation features on site, it may well be necessary to limit flow from the attenuation feature, to the outlet. Whether this be a river or a sewer. These are also sometimes referred to as a hydraulic brake.

Capacity Enquiry to Thames Water or Anglian Water

If need be as part of the Surface Water Management Plan or Strategy we can carry out an application to your local water company / or sewerage undertaker (sometime the same company) and check if it is OK to put surface water in to their surface water sewer system.

Surface Water Management Case Studies

Below are a selection of surface water management reports that have been listed on our project blog:

Please feel free to contact the office for an informal discussion regarding your requirements.