From April 1^st, 2019, London based developments involving a drainage strategy are required to have the relevant Sustainable Drainage Proforma accompanying them when a planning application is submitted.

The London Sustainable Drainage Proforma (LSDP) is essentially a standardised set of queries that need to be answered. There were many London boroughs that already had a Proforma in place, such as Croydon. However, this new Proforma covers each London borough individually and ensures all of London is to the same standard.

In essence, the London Sustainable Drainage Proforma are there to speed up the assessment process and prevent delays in planning approval as all the key information will be seen upfront by the Lead Local Flood Authority (LLFA).

There has been a big shift in policy in recent years with more emphasis being placed on developers to ensure they are managing surface water in a sustainable way. Many planning applications now require surface water drainage information that may not have done 10 years ago. The LLFA’s simply don’t have enough manpower or time to review the increase in number of planning applications with surface water drainage strategies.

Furthermore, some surface water drainage strategy reports can be fairly complex documents often with supporting micro drainage calculations for existing/proposed developments, site investigations, as well as details regarding relevant national and local policy. This has led to LLFA’s needing to streamline the process as much as possible, hence the London Sustainable Drainage Proforma.

It’s only required when a drainage strategy, or SuDS, is being submitted with a planning application within one of the 33 London Boroughs.

There are 4 sections to the Proforma. These are:

1.      Site and project information

This is essentially an introduction to the site and what you plan on doing to it. It details the current site, development proposals, and whatever the existing drainage is.

2.      Proposed discharge arrangement

This section gives a summary of the ground conditions in order to determine whether infiltration is feasible for the proposed development. This includes during construction and post development, as well as the drainage arrangements with reference to the drainage hierarchy as set out within the London Plan.

3.      Drainage Strategy

This section contains the runoff rates for pre and post development and the proposed SuDS measures. As you can expect, it will prioritise SuDS measures that manage runoff as close to the source as possible in order to contribute to the four main pillars of SuDS; amenity, biodiversity, water quality, and water quantity.

4.      Supporting information

This is both a summary of the information as well as a sort of reference section. Here, you’ll cross reference to the full drainage strategy to more detailed information which supports each element of the LSDP.

An example of this could be to the full utility plans, SuDS designs, and maintenance strategies.

The short answer here is: It won’t.

We know it may concern some of our clients, or the planning industry in general, that this means additional work and inevitably additional costs. We’re here to tell you that it shouldn’t. If anything, it’s designed to save you time and therefore any extra cost that comes with delays, it also promotes consistency across the London Boroughs, so the design parameters and requirements are the same, reducing the uncertainty.

For us in particular, it won’t affect our client’s drainage strategies at all. Of course, it’s important that those looking to develop a site are fully aware of their obligations when it comes to the Proforma. However, the additional level of detail necessary to meet these requirements are already included within our drainage strategies so from our perspective, no real change is needed.

Of course, we can’t speak for other drainage consultants so you’ll have to research other companies reports yourself.

If you’d like to talk more about how the new London Sustainable Drainage Proforma will affect your development, or just get some advice about drainage for your site, email our drainage team at [email protected] and one of our drainage experts will get back to you.