Everybody living or working in the Calder Valley can make small changes to slow the flow of stormwater.

Many small interventions, to slow run-off, could result in a significant amount of water being temporarily stored during storm events in our urban areas.


This will help to reduce peak flows (see the detailed Storm Hydrograph) which, together with catchment management and traditional flood defences, would contribute to reducing the scale and damaging effects of flood events.


Principles of SuDS

Sustainable Drainage Systems (SuDS) mimic the natural cycle of water management, by retaining water where it lands (instead of shedding it quickly to drains and watercourses, which can lead to floods).

roadside swales collect and filter rainwater

Roadside verge transformed into a Rain Garden

SuDS reduce rainwater runoff from a given site, filter it to improve water quality, and slow its journey downstream.

Sustainable drainage allows us to Slow The Flow in Calderdale’s urban environment. This complements rural Natural Flood Management (NFM) measures. SuDS and NFM are in fact describing the same thing, but SuDS is more often the term associated with the urban environment.

We can also consider altering our behaviour during flood events to discharge less water into drains (much as we might behave to conserve water during drought).


During and after the devastating Boxing Day Flood 2015, thousands of us gave our time and money to help friends, family and neighbours recover.

If we all work together to take action and invest in our own properties (whether they flood or not) we can help reduce the threat of similar levels of flooding in the future, and the need to help clean up on such a large scale.

retrofit rain garden next to concrete driveway

Rain Garden in a small space

If every person in Calderdale (200,000 approx) stored an average of 0.1m³ (about a half-full bathtub) of water in a flood event, we could store around 20,000m³ (about 5 m³ for every property that flooded on Boxing Day 2015).

This could make a real difference, especially to water quality in areas which suffer from sewer flooding.

Retrofitting urban SuDS is also a chance to contribute to local Green Infrastructure, improving:

  • wildlife value
  • air quality
  • the appearance of your property.


Urban SuDS might include:

Roadside verge Rain Gardens, Scunthorpe

Roadside verge Rain Gardens, Scunthorpe

Quick Wins

Sign up to receive Environment Agency Flood Warnings (even if you’re not in a flood zone)

Make water butts into ‘mini leaky dams’ in winter! Leave the tap open slightly before a storm so they can drain down, then act as mini dams, slowing the rainwater from your roof.


Be a Water Hoarder!

Help to prevent combined sewer overflows by altering your actions during flood events to discharge less water into drains (as you might in drought - e.g. shower rather than bath, wait to use the washing machine...)

Yorkshire Water provide tips and free water saving packs.

Green Roofs on domestic sheds, North Cave

Green Roofs on domestic sheds, North Cave



Locations such as:
  • Back Gardens
  • Front Drives
  • Sheds
  • Bin stores
  • Roadside verges
  • Public spaces
  • Central reservations
  • School grounds
  • Car parks
Permeable path and bin store green roof, RHS show

Permeable path and bin store green roof at RHS Hampton Court Show ‘Greening Grey Britain’ Demonstration garden

Swale at the Olympic Park: fills up only in heavy rainfall

Swale at the Olympic Park: fills up only in heavy rainfall


General Principles

Visit the page or download our printable 2-page PDF to get started

Hints, tips and links to SuDS information that are useful to everybody

Slow the Flow: in your life and work

How to make it happen in the places that matter to you!


Visit our 'SuDS Links' page for further information

Watch the videos of our public meeting on this topic:

Amanda McDermott presents on why and how urban SuDS can be used to Slow The Flow - at Work, at Home, at School, and in Public Spaces.

Chris Griffiths demonstrates the principles of slowing the flow with urban SuDS using a specially built model, and a watering can.

Let us know how you Slow The Flow!

Share your stories and photos:




You Can Slow The Flow has been kindly sponsored by our friends in the Calderdale Flood Partnership, through the SOURCE partnership, and created by 2B Landscape Consultancy Ltd