Does Drainage Remove Flood Risk?


 Whilst well designed and robust drainage systems can reduce the risk of flooding, it is important to remember that they cannot remove the risk of flooding. Drainage systems are all designed with a ‘return period’ in mind, i.e they will work effectively up to a point where there is a storm event which exceeds their design capacity and overwhelms the drainage system, resulting in potential surcharge and flash flooding. This is why drainage is seen as part of the jigsaw of flood risk management, with residual risk still managed via Property Flood Resilience and Flood Insurance. The limiting factors with drainage are usually related to site limitations (sizing and topography), along with budget.

In many instances, it is possible to minimise and reduce the risk of flooding through effective and efficient drainage design. To ensure the drainage design is suitable and cost effective, we would highly recommend that it is modelled in drainage modelling software prior to finalising any designs or installation. Modelling software can include the likes of Microdrainage or Infordrainage. Our team are well versed with this software and would be able and willing to assist with your project.

By directing and channelling water away from building, roads, or other infrastructure, properly designed drainage can reduce the risk of flooding. This can be through reducing the amount of water that collects in a particular location, for example by collecting and diverting water away from a property’s foundations, a well designed drainage system can lower the risk of basement flooding. An effective channel drain could also reduce the risk of water entering any low level airbricks around a property, helping reduce sub-floor flooding.

By controlling the water flow and lowering the probability of flash flooding, sustainable drainage systems can vastly  aid in lowering the risk of flooding, not just at the development site, but also for surrounding areas. This can be accomplished by utilising stormwater control strategies such as green infrastructure, detention basins, and balancing ponds.

It’s important to remember that drainage systems may become overloaded during severe weather, Other precautions like flood barriers and evacuation plans should also be taken into account in these situations.

What Makes Drainage Effective?

Effective drainage depends on several key factors:

  1. Proper design: The drainage system must be properly designed to handle the topography and site conditions, taking into consideration aspects such as the area that needs to be drained, the catchment, the slope of the land, the surface covering and types of soil. This is best achieved through drainage modelling, and our team are experts in this field to assist you.
  2. Adequate capacity: Drainage systems should be sized to cope with the volume of water that is expected to flow through them in regular rainfall events.. In order to manage the water without overflowing or clogging, the size and quantity of drainage channels, pipes, and other components must be adequate. This sizing can also be determined through drainage modelling.
  3. Suitable Installation: The drainage system needs to be set up properly, using the right tools and components. In addition to making sure that the drainage pipes and channels are graded and connected correctly, this also entails putting in any required backflow valves or other control mechanisms.
  4. Regular maintenance: To make sure the sewage system keeps working efficiently, regular upkeep is essential. This entails clearing out any sediment or debris that may have gathered in the drainage pipelines or channels and checking that all control devices are operating correctly. As part of a life cycle risk assessment when designing the system, maintenance should be considered.
  5. Proper vegetation: By absorbing water, slowing down runoff, protecting the earth, and decreasing erosion, vegetation helps with drainage.
  6. Regulations: Drainage systems must adhere to all applicable building and land drainage rules.

In summary, an effective drainage system should be designed and built to handle the volume of water that will be flowing through it, installed correctly, maintained regularly, and be part of an overall water management strategy that includes proper regulations compliance.

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