SUDS: Sustainable Urban Draining Systems03/12/13 4:01 AMKey Points:1. Water meters have been shown to reduce household water use by 5% to 15%.2. Water meters also help to monitor the effectiveness of water saving devices.3. Composting toilets require virtually no water.4. Separating water uses such as drinking/flushing for potable/recycled water may require separate infrastructure.5. Could water used to keep dust levels down on construction sites be recycled or can prefabrication minimise this wastage?

Design Procedure:Step 1:Establish whether water usage can be reduced by lifestyle or business design changes such as composting toilets, showers instead of baths, and less water intensive facilities (such as reduced wash down areas, passivecooling of data centers).Step 2:Identify appropriate water saving devices such as low flow taps, electronic sensor taps, low flush toilets, time restricted showers (widely used in Australia), and efficient washing machines. These flow rates can be used to calculate the overall water use, more accurately than generic per person guidelines. The Code for Sustainable Homes provides a water calculator.

Step 3:Identify the capacity for rainwater harvesting (see rainwater harvesting) to identify how much can be provided without using mains supply potable water. Offices typically use less than a third of the water per person per day of households and are only operational five days a week. Therefore it may be possible to provide all of the water supply from rainwater harvesting or recycling.

Step 4:Identify the water usage in the building, whether it has to be potable (drinkable) or can it be re-used elsewhere?

Step 5:Identify if it is possible to recycle wastewater. It is possible to treat all wastewater to drinking standard though it is more common to recycle grey water (from showers, washing machines etc) and use for flushing toilets.

WATER CONSERVATION03/12/13 4:01 AM

Rainwater harvesting is a design measure to collect, store and re-use water. This takes the form of collecting surfaces such as roofs or pavements (to harvest rainwater), linked to storage vessels, such as water butts or underground tanks (to store water),sometimes combined with pumps andfiltration systems (to recycle the water). There are two types of system, direct feed or header tank. Direct feed is the most common, with the tank linked directly to the use, such as garden. With a header tank harvested rainwater is pumped into a tank, typically in the loft, and mixed with mains water

Key points:1. Rainwater tanks need to be located away from direct sunlight to avoid algae growth.2. Underground tanks help to moderate temperature, reducing bacteria growth in the summer and frost in the winter.3. Check if the area is susceptible to flooding.( If an area is also at risk of flooding, the risk of contamination of the water supply must also be considered.)4. Tanks larger than 5% of the water demand are sometimes found to be uneconomical.5. Water run off from pavements or drives needs to be filtered, increasing cost.Design procedure:Step 1:Identify if the entire building needs to be provided with drinking water or if rain water or recycled water can be used in areas.Step 2:Determine the quantity of water used overall. It is possible to calculate this using generic water consumption rates. As a rule of thumb new households use around 150 litres per person per day (l/p/d), metered houses use 136 l/p/d and older households use around 167 l/p/d. In a typical office the average use is 50 l/p/d.Step 3:Determine the proportion that is required for drinking, washing and flushing toilets/ low grade industrial uses. Use this to determine the quantity of water that could be provided by rainwater harvesting or recycling. In a new household at least 35% of water could be provided by rainwater.Step 4:The size of a rainwater tank should be based on water demand, annual rainfall and the size of the catchment area (roof and/or paving).

Harvesting rainwater for domestic uses: an information guide, tank size:

effective collection area (roof) x drainage coefficient (based on roof angle, 0.8 for pitched roofs) x filter efficiency (typically 0.9) x annual rainfall (apx 850mm) x 0.05 (5% guide)

Step 5:Determine the best location for the tank depending on the system (direct feed or header tank). Consider the quality the water needs to be treated to.

Rainwater harvesting system.

RAIN WATER CATCHMENT03/12/13 4:01 AM

Key points:1. Consider which areas of the site are most at risk of flooding.2. Flood risk may be different across parts of the site.3. Identify if the use proposed is likely to put peoples lives at risk if a flood occurs (at any time of the day or night).4. Determine whether it is possible to locate the building in a different part of the site or if it would be better located on another site altogether.5. Consider changing the use of the building to make it less susceptible to flooding.Design procedure:Step 1:Identify if the site is at risk of flooding. The Environment Agency website and the Local Authority can provide details.

Step 2:Determine if and how this might change in the future due to climate change. Planning policy gives guidance on how climate change should be calculated. The Local Authority can provide maps and information on your area.

Step 3:Establish the area of the site most susceptible to flooding and the likely depth and extents of a flood. Identify if it is possible to locate the buildings away from areas at risk of flooding.

Step 4:Establish whether the uses of the buildings are appropriate for the site and whether it would be necessary to relocate or change the building use, if this is not possible then you would need to introduce other design strategies such as building resistance or resilience.

Step 5:Locate your access on the side least at risk of flooding and seek to locate above the height of the floodwater, in accordance with policy guidance and best practice.

Step 6:Orientate the building in line with the direction of flood flows to reduce the extent of the obstacle to flood flows.BUILDING PLACEMENT(FLOOD RISK)03/12/13 4:01 AM

Resilience is a design measure that can reduce the damage that occurs to buildings from flooding. It does not prevent floodwater from entering a building. It involves constructing a building in such a way that although floodwater may enter the building, its impact is minimised (i.e. no permanent damage is caused, structural integrity is maintained and drying and cleaning are facilitated). Typically this is referred to as flood resilience and it could equally apply to earthquakes or fires.

WHEN TO USE IT?Resilience measures should be used on buildings in areas that are known to be at risk of flooding, may be at risk of flooding in the future or have a history of flooding. Typically resilience would be used when other measures to locate buildings away from flood-risk (placement), above the maximum flood level or that prevent water from entering the property (resistance) are not appropriate. Generally resilience should be considered where flooding is likely to be over 600mm deep or fast flowing and could cause structural damage.

Key points:Consider the depth of flood water within the building (most objects will float in 300mm of water).Can susceptible uses, such as kitchens be located on higher floors?Basements are not permitted in flood prone areas.Floodwater can rise from the floor, not just come in through the doors and windows.Objects inside and outside buildings may float and could collide with the building.Embodied energy of resilient materials such as plastic or concrete.

Design procedure:

Step 1:Identify how deep the floodwater may come against/within the building (it is also important to understand the speed of the water and whether it is likely to carry debris). This is not always as easy to identify as it sounds. Consult your local council for more details

Step 2:Determine if it is possible to prevent water from entering the building. Typically if the depth of water is greater than 600mm then resilience will be the most appropriate design measure. Additionally if there are a lot of openings in the building then it may be preferable to allow water into the property rather than try to waterproof every junction.

Step 3:Identify all of the materials, fittings etc that will be affected when flooded (allow an additional 300mm to the flood depth for tolerance). It is important to consider the construction and composition and not just the surface finish, as water is likely to penetrate through the whole building fabric

Step 4:Determine if it is possible to reorganize the building to put more vulnerable uses higher in the building and/or create level changes subject to disability access constraints to reduce the impact of flooding. Determine whether there are different levels within the building to see whether other water proofing technologies might be appropriate

Step 5:Seek to locate all services, electrical fittings, white goods and sanitary ware above the maximum flood level. Consider that anything located below the flood level will get wet, including wiring, telephones etc. Choose materials that are resilient to water and try to integrate these into the design. This may require using hard surfaces below the maximum flood level, such as tiles or stone. Solid walls may still get saturated during a flood but should also dry out (particularly if breathable lime mortar is used).

FLOOD RESILIENCE03/12/13 4:01 AM

Key points:1. New buildings should be located out of flood-risk where possible.2. Flood resistance typically requires human intervention to implement actions to protect the building, this means that ample warning time needs to be available to set up defences.3. Consider how waterproof the building fabric is (type of frame, type of infill panels, floors, walls).4. Floodwater can rise up from the ground, not just enter through doors, windows or other openings.5. It is necessary to determine the structural integrity of the building, deep water can cause structural damage.6. Use certified waterproof sealants and materials to dry proof the building.7. Consider pipes in and out of the building as potential paths for water.

Design procedure:Step 1:Identify how deep the floodwater may come against/within the building and identify if this will change in the future, as a result of climate change. This is not always as easy to identify as it sounds. Consult your local council for more details.

Step 2:Identify if it is possible to elevate a proposed building above the flood level or to elevate it sufficiently to reduce the depth of floodwater likely to occur to below 300mm.

Step 3:Typically if the depth of water is greater than 600mm then resilience will be a more appropriate design measure. Additionally if there are a lot of openings in the building then it may be preferable to allow water into the property rather than try to waterproof every junction.

Step 4:Identify all of the openings around the exterior of the building, and determine how wide are they? Proprietary door guard products are typically designed for single domestic doors. Consider if it is possible or appropriate to reduce the number of potential openings / water pathways into the building.

Step 5:Identify any additional pathways that water could enter through such as drains, undercrofts, air bricks etc. During a flood a differential in water pressure can be created in WCs resulting in water spewing out of WCs. Determine which corresponding product is suitable for which area of the building

FLOOD RESISTANCE03/12/13 4:01 AMStep 6:Make sure every possible entrance is protected, if you miss something, the floodwater will find it! Good workmanship is essential to avoid holes in construction, which could form flood pathways

1. Sustainable Urban Draining Systems (SUDS) such as rain gardens and green roofs are an engineered means to manage rainwater run off such that it emulates natural drainage systems. 2. SUDS employ various techniques to effectively manage drainage which includes green and brown roofs, dry ditches (swales), detention/attenuation ponds, permeable paving, underground storage tanks and many other measures, all of which aim to detain run-off and release it slowly into watercourses or to ground.

WHEN TO USE IT?SUDS should always be used in preference to conventional drainage when possible. If SUDS were to be incorporated into existing developments peak run off rates could be reduced and therefore flood-risk overall could be reduced. Different measures may be more or less appropriate depending on location and conditions, such as use, existing pollution, geology, area available and whether a site is at risk of flooding. SUDS are particularly beneficial during extreme weather where conventional drains would be overwhelmed. SUDS are becoming more widespread in the UK, benefiting water quality and flood management.

Key Points:1. In most cases it is beneficial to use a combination of techniques.2. Gravity systems require natural falls across the site.3. Brownfield sites may contain contaminants.4. Presence of pollutants either prior or potential (this includes run off from roads and parking areas).5. The disposal of roofwater. For example, it may be possible to discharge roofwater onto a garden area, where it can soak into the ground.6. Maintenance and upkeep, particularly of surface level measures such as swales.

Design procedure:Step 1:For Greenfield sites SUDS are designed to mimic Greenfield run off rates (ie such that the site acts as though it were a natural green site). For Brownfield sites SUDS must be designed to mimic the existing run of rates, including allowing for climate change, as a minimum but ideally to mimic green field rates.Step 2:Existing run-off rates or green-field run-off rates must be calculated based on the site area, area of impermeable surfaces and geology. Calculation of SUDS can be complex as different storm durations and scale (up to a 1% probability rain storm) must be considered as well as the permeability of the ground conditions the height of the water table and the impact of climate change.Step 3:Where possible SUDS should allow water to filter into the ground (infiltration), mimicking natural processes. However, if the site has been used for industry it may contain pollutants therefore making infiltration inappropriate. Equally if the ground is predominantly clay or there is a high water table the run off rate may be so low that permeable solutions may be ineffective.

Green roofs and walls.

Permeable paving.

Step 4:Hard surfaces such as roofs and roads result in increased run-off rates over green surfaces. Green roofs and permeable pavements will help to reduce the run-off rates closer to green-field rates. Systems that slow the rainfall before it gets to the ground, such as green or brown roofs and green walls, are also universally beneficial and will continue to reduce run-off rates even in flood-prone areas.Step 5:If it is not possible to use infiltration devices, and/or permeable surfaces are insufficient to reduce run-off rates sufficiently then flood storage devices may need to be considered, these can include dry ponds swales, basins but also underground storage (typically pumped). Communal rainwater harvesting tanks may be considered, however they are often far smaller than required for large rainstorms.Step 6:Ground level SUDS such as swales or rain gardens can achieve water quality and environmental improvements, through habitat creation or amenity provision. When interspersed between parking areas and buildings they can also create visual interest. However, maintenance and protection of use must be considered.

Swales integrated with public realm and allotments.

Rain gardens and swales.

Filter strip divides parking bays.