Sustainable drainage and the planning process in England The National Planning Policy Framework (NP) and its associated technical guidance that replaced Planning Policy Statement 25 (POSS.) in 2012) states that priority should be given to sustainable drainage and discusses the impact of new development on flood risk. The NP maintains strong policy on avoiding and managing flood risk. Based on local planning authorities preparing local plans and deciding planning applications and granting planning permissions.
Design criteria Setting the design cartel at the start of the project and establishing a clear SuDS vision ensures that the SuDS scheme and/or components are not secondary to other requirements for the site. Sustainable drainage should be Integrated into the urban arm, whether using hard engineering or soft landscaping features. Design criteria (as set out in table 1) for the SuDS scheme provide a useful framework for delivering a scheme that meets objectives agreed by the client and design team. These will ideally relate to flood risk management (water quantity), water quality, and the provision of biodiversity and amenity.
It may not be possible to maximize opportunities for all three objectives and the extent that this happens should be discussed with the relevant stakeholders. More specific guidance on the design criteria can be found In COCA the SuDS Manual Table 1: Considerations for design criteria Design cartel Key principles Water quantity (hydraulics, flooding, runoff etc) People and property must be protected from all flooding sources, including local watercourses, the development’s drainage system and overland flows. Development should not exacerbate flood risk within the wider catchments.
The flow rate and volume of runoff should be managed to agreed levels and drainage exceeding should be considered. Water quality (pollution control, management etc) Potential pollution risks should be mitigated by the use of source control, the SuDS management train with the appropriate number of treatment stages. Amenity and biodiversity SuDS can positively influence urban design and landscape value through provision of green space, vegetation integrating water into the built environment, providing opportunities for biodiversity. Sustainable drainage is to be included in public open spaces and contribute to green infrastructure. Healthy and safety concerns should be addressed and designed out. SuDS components should have shallow side slops, and ponds should have shallow shelving edges, and make good use of vegetation to prevent access. Often and amenity and biodiversity is dependent on water quantity and quality being effectively managed.
The design process Good urban design is only possible where the design and management of water in a scheme is integrated as an important part of the whole concept. SuDS can be designed without urban design input, but this leads to the creation of water management features that are disconnected with the character and aesthetic of the place, known as the ‘context’. Having an inter-disciplinary team (if not transcendentalism) will help deliver a robust scheme with multiple benefits. Design selection
Sustainable drainage systems are designed using the same underlying principles of hydrology and hydraulics as traditional drainage systems, but also need to embrace the wider opportunities for managing water quality, environmental enhancement, amenity, community acceptance and urban design. Principles When selecting SuDS it is important to consider water quality, water quantity and amenity design criteria equally. There will not be a single “correct” answer: several options may meet the design criteria, and Judgment will be needed.
It may not be possible to maximize all three design criteria as this is likely to reflect the opportunities and constraints on site. Selection and design of SuDS are multi-disciplinary processes. Unlike traditional drainage systems, factors that influence the final choice will include planning, water quality, water resource, architectural and landscape requirements. The selection process Once an initial assessment of the site has been made and the design strategies for the drainage system have been agreed, drainage components can be selected.
The selection process in based on the principles that: The drainage scheme complements the overall vision for the site and management of surface water Drainage monuments will be used in series (the SuDS management train) to meet the design criteria for water quantity, quality, amenity and biodiversity Drainage components at the top of the management train are generally to be preferred to those further downstream There is no single correct solution; selection may be the result of site opportunities and constraints Minimize the use of impermeable surfaces wherever possible Maximize opportunity for managing water at or near the surface Source control is environment The SuDS scheme should be inspired by the original drainage pattern and characteristics of the local area. The SuDS scheme should be designed to facilitate maintenance and operation. The process is cyclical, and various factors have to be considered in increasing detail as a final solution is approached.
The selection of individual components and the SuDS scheme will depend on a variety of site attributes and factors including: local hydrology and hydrology ground contamination depth of water table soil permeability ground stability sensitivity of receiving waterbeds (either surface water or groundwater) size of catchments area development type, density and required layout requirements for local flood risk management there opportunities within the overall site affordability of scheme (capital and operational) HTTPS://mail. Google. Com/mail/u/on Table 1: Key considerations for SuDS construction Programming Normally traditional drainage is one of the first elements of infrastructure constructed on site.
For SuDS, although the form of the drainage will be constructed during the earthworks phase, final construction should not take place until the end of the development programmer, unless adequate provision is made to remove any silt that is deposited during construction operations, and refurbish any areas that have en subject to overcorrection, isolation etc. The contract is likely to stipulate establishment of landscaping vegetation, and sediment removal sometime after site works have been completed and prior to commencement of the maintenance period. Pollution and sediment control Surface water runoff from the construction site should not drain into SuDS components unless it has been allowed for in the design and specification.
Construction runoff can be heavily laden with silt, which can clog infiltration systems, build up in storage systems and pollute receiving waters. No traffic should be allowed to run on permeable surface components if it is likely to cause clogging of the pavement surface or result in overcorrection. Access and storage areas constructed) during the initial stages of the development, and then used as access roads and storage areas. If permeable surfaces are proposed, pavement construction should be carried out at the end of the development programmer, unless adequate protection is provided to prevent clogging or blinding once it has been constructed, otherwise rehabilitation to remove clogging (I. E. Action sweeping for permeable pavements) may be required. Skills and understanding The contractor and all relevant operatives should have an understanding of the purpose, operation and function of the SuDS components to ensure appropriate construction practice and protection is used. This relates to the conveyance (gradients), infiltration (quality of soil) and storage of surface water runoff. Infiltration system protection If SuDS components are to be lined, the use of hardcore for structural purposes below the level of the liner can be accepted. However the use of hardcore is not advised if infiltration is intended, due to the high proportion of fines generally resent.
Sensitive ground, such as Chalk, may require the use of total exclusion zones for construction traffic to prevent compaction and other damage to the ground that will affect the infiltration performance. This may include protection from runoff during construction if the component is located at a low point on the site. Risks primarily relate to compaction and isolation of infiltration components. Landscaping The importance of good landscaping should be emphasizes. As SuDS are normally at, or on the surface attention to detail and aesthetics must be given a high priority. The seasonal and physical requirements of planting and establishing vegetation and prevention of soil erosion should be programmed appropriately.
Appropriate operative skills with an understanding of all aspects of vegetation are required. Appropriate attention to detailing and ground levels for components should prevent any overland sediment wash off during high intensity rainfall events, or groundwater seepage during wet periods. It should also allow the appropriate overland flow of water around the SuDS scheme, lee water flows downhill. Erosion control Before runoff is allowed to flow through on the surface vegetated SuDS components (egg swales) they should be stabilized by planting or temporary erosion protection. This will reduce erosion and the clogging of other HTTPS://mail. Google. Mom/mail/u/on Handover inspection Provision should be made in the construction contract to review the performance of the SuDS when it is completed, and to allow for minor adjustments and refinements to be made to optimism the physical arrangements, based on observed performance. Suitable site supervision and inspection is also useful to ensure the SuDS monuments and scheme have been constructed as designed. Specification and bills of quantities Designers should highlight particular matters associated with the above points that are likely to impact the operation and performance of specific SuDS systems. The type of specification and/or bills of quantities will depend upon the form of construction contract being used for the specific project.
Module name: Sustainable Building (Specialist teaching – 10 credits) Sustainable building design aims to create resource-efficient buildings that are comfortable and healthy places to live and work. Materials, water and energy are seed for the construction and the running of buildings and the use of resources can be associated with environmental and social impacts. Sustainable design ensures that the impacts associated with resources are kept to a minimum while also considering issues of light, temperature, indoor air quality and psychological aspects of buildings that affect health. This module focuses on the design to minimize resource use, while considering the need to create healthy environments.