Flooding is a serious problem for many people in the UK during Autumn. When rivers rise unexpectedly and overflow their banks, they can flood houses—this is known as river flooding, which is distinct from groundwater flooding. Rainwater can also reach the coast via storm drains and cause coastal floods.
- Groundwater flooding can affect any type of building, seeping through foundation cracks and causing damage.
- Early signs of groundwater flooding include overloaded sewers, damp patches, and unexplained water in basements.
- Prevention measures vary based on the type of flooding and may include underground drainage systems.
- The Type C cavity drainage membrane system is a popular choice for managing basement flooding without structural modifications.
- Groundwater flooding risk assessment requires site-specific evaluations for areas with high risk.
What is Groundwater Flooding?
Groundwater flooding is an issue that affects many buildings around the UK. The British Geological Survey (BGS) estimates that around 122,000 to 290,000 properties in England are at risk of groundwater flooding. In some places, the problem may not be noticeable until after heavy rain falls. However, if the water table rises too high, it could cause damage to the foundations and walls.
Perched aquifers are becoming increasingly common. They occur when there is an increase in the groundwater table because of rainfall. Water enters the ground through small holes in the surface, or through a broken pipe or drain. When groundwater levels rise significantly, a spring can form, causing water to emerge at the surface and potentially leading to localized flooding.
In order to prevent flooding, it is important to know what kind of groundwater you have. Some types of groundwater cannot be stopped by conventional means. For example, if your property sits on top of an aquifer (a layer of porous rock), then water can enter your home without any warning.
Impact of Groundwater Flooding
Almost any type of home or structure can be impacted by groundwater flooding. Water usually seeps through foundation cracks and into crawlspaces or basements. Runoff from heavy rainfall, especially when drainage is poor, can also contribute to the overall water entering the property. Once this happens, it could result in structural damage and the growth of mould, harming your home or business. Water damage can happen very slowly; it can take days, weeks, or even months for it to happen. Water can occasionally stand still for a long time before beginning to damage your property.
If flooding is not controlled, it can lead to major issues. Groundwater and surface water both have the potential to flood properties. When tainted groundwater seeps into basements and rises above the floor, it causes groundwater flooding. Cracks in the walls, floors, drains, pipes and foundations allow contaminants to enter the building.
When contaminated groundwater reaches the basement, it flows into the foundation wall and then moves upwards towards the ceiling. Once it reaches the top of the basement, it escapes through the roof and contaminates the air we breathe.
Where is Groundwater Flooding most common?
In parts of England, the ground is prone to floods, and traditional landscapes including valleys and hillsides are generally associated with groundwater. However, cities aren’t immune either, groundwater can rise in places with soil, sand, and gravel as well.
In recent times, the city of London has faced a lot of problems related to the water supply. Homes all across the city are facing issues due to heavy rainfall and rising groundwater levels. Basement flooding is one such major issue that homeowners face. If you’re more susceptible to groundwater flooding, you may not be able to completely prevent flood water from entering. However you can take steps to safeguard your home or business.
Groundwater Levels and Flooding
Groundwater levels are a key factor in determining the risk of groundwater flooding across Great Britain. When the water table rises and reaches the ground surface, the risk of flooding increases dramatically, especially in areas with permeable superficial deposits or chalk bedrock. According to the British Geological Survey, groundwater flooding occurs when the natural underground drainage system cannot drain rainfall quickly enough, causing water to accumulate and sometimes emerge as new springs. This process can result in significant flood hazard, with surface flooding that may persist for weeks or even months.
The risk of groundwater flooding is particularly high in river valleys and rural communities, where the geological infrastructure—such as aquifers and permeable soils—allows water to flow and rise more easily. In England, many rural communities and individual properties have experienced the emergence of groundwater flooding in recent years, with basements, underground rooms, and ground-level areas especially vulnerable. The increased frequency and longer duration of flood events highlights the need for further research and careful assessment of flood risk.
Local authorities, including county councils and local councils, along with the Environment Agency, play a crucial role in managing groundwater flood risk. They provide relevant information, guidance, and support to help residents stay safe during flood events. The process of groundwater flooding is often triggered by prolonged rainfall, which saturates the soil and overwhelms the natural drainage channels. As the water table rises, new springs can appear, and flood waters may affect properties that have never previously flooded.
Assessing the risk of groundwater flooding requires a thorough understanding of the local geology, the range of groundwater levels, and the nature of the drainage system. The British Geological Survey and Environment Agency offer valuable data and resources to help assess and manage this hazard. By staying informed and following the advice of local authorities, property owners can better prepare for and respond to the risk of groundwater flooding, reducing the impact on their homes, land, and communities.
Signs to Watch Out For
Water may enter your home through doors, windows, or drains. Flooding can also come from rivers, streams, lakes, reservoirs, oceans, underground aquifers, and storm sewers. Floods caused by rain, snow melt, and heavy storms can affect buildings, roads, bridges, and utilities. There are a few warning signs that can help you identify if your home is at risk of being affected by flood waters.
- Local sewers are overloading and overflowing
- Damp patches appearing in lower levels of the property
- Water in your cellar/basement with no source
These warning signs may indicate local flooding due to site-specific conditions that are not always captured by general flood maps.
The code of practice concerning flood protection in underground structures states that risk should not be neglected for any basement or cellar, no matter how small. Although there are currently no indications, problems may occur in the future. Recent bad weather conditions have shown many unprotected cellars, meaning if your cellar is presently unprotected then now would be an ideal time to think about waterproofing.
How to Manage Groundwater Flooding
Flood prevention depends on the type of flooding you want to avoid. Sandbags can only protect against surface water and won’t stop groundwater from entering your home. Installing an underground drainage system to channel excess water away from your property is a better option. Incorporating a drainage channel as part of this system can help direct excess groundwater away from your property, reducing the risk of groundwater flooding.
There are many flood control and drainage systems available. The best one for your home depends on several factors. Consulting an expert can save you money and stress to find the right solution.
Type A Barrier System (Tanking)
The most commonly seen waterproofing method is the Type A or “Tanking” system. It involves the application of a waterproof render or tanking slurry on the surface. But using only on this approach might be dangerous. A solid bond between the render coat and the wall is necessary for a successful rendering process. Hard brick walls might make this difficult because they don’t naturally stick to the render coat. Render coats may fail and allow moisture and even flooding in the case of inadequate binding. Cracks in the render coats may also result from structural movement.
Type C Cavity Drainage Membrane
The Type C drainage system is a popular and reliable solution. It involves installing a polymer studded floor with drainage channels leading into a sump and drain. Water enters the cellar through these channels and drains into an outlet near the ground. This method requires no structural modifications to the foundation, making it popular among homeowners who want to improve their basements without extensive construction. Before installing this system, research and consider getting professional help if you’re unfamiliar with plumbing.
Groundwater Flooding: A Risk to be Aware of
Groundwater flooding occurs when groundwater levels rise above the natural ground level, potentially flooding your house even without rain. Changes in the land’s surface due to erosion, construction, or underground mining can cause water table rises. These changes allow water to move into areas where it wouldn’t normally go. To prevent flooding, ensure new construction doesn’t disturb the soil beneath your property. Installing sump pumps can also help drain excess water from your basement.
Groundwater Flooding Assessment
Although it isn’t always possible to completely avoid groundwater flooding, you can take precautions to prepare for any future considerations. For the majority of low-risk locations, a preliminary screening evaluation is adequate. Regions at increased risk of groundwater flooding, however, will require a more thorough, site-specific evaluation.
A site’s potential vulnerability to groundwater flooding can be determined with the help of the Groundwater Flood Risk Map. This map shows whether groundwater flooding is a possible risk and offers advice based on the modelled risk level. It is available at several scales and risk resolutions. Although useful, the map shouldn’t take the place of an extensive site-specific evaluation. In addition, the county council and local council can provide guidance and support for flood risk assessments and for reporting flooding incidents. A thorough risk assessment is necessary in locations where substantial damage from groundwater flooding is possible.
Conclusion
Groundwater flooding poses a serious threat to homes and businesses, especially during heavy rainfall. It is imperative to be educated about the risks and about the appropriate measures needed to manage the risks. Properties must be protected by routine inspections and preventative measures like installing drainage systems. Stay proactive and consult experts to ensure the best protection against groundwater flooding.
What is groundwater flooding?
Groundwater flooding occurs when water from below ground seeps into buildings through foundation cracks or other openings due to a rising water table.
How does groundwater flooding differ from surface water flooding?
Groundwater flooding originates from the water table rising beneath the ground, while surface water flooding comes from heavy rainfall or overflow from bodies of water on the surface.
Can groundwater flooding occur even without heavy rain?
Yes, groundwater flooding can happen without heavy rain if the water table rises due to factors like erosion, construction, or underground mining.
What immediate actions should I take if I notice signs of groundwater flooding?
If you notice signs such as damp patches or water in your basement, contact a professional immediately to assess the situation and implement temporary measures like sump pumps to control water levels.
What are the health risks associated with groundwater flooding?
Groundwater flooding can lead to mould growth and structural damage, posing health risks such as respiratory issues, allergies, and infections from contaminated water.
What long-term solutions are available to prevent groundwater flooding?
Long-term solutions include installing underground drainage systems, using waterproofing methods like Type C cavity drainage membranes, and ensuring new construction doesn’t disturb the soil beneath your property.
How often should I inspect my property for potential groundwater flooding issues?
Regular inspections, especially after heavy rainfall or significant construction activity nearby, are recommended to identify and address potential groundwater flooding issues early.
