CHURCH LANE AND WOODVIEW COTTAGES AS WELL AS RATHFARNHAM MILL

FLOOD RISK

Rathfarnham Village and its Proximity to the River Dodder

This article delves into the history of flooding in Rathfarnham Village, Dublin, specifically examining Church Lane, Woodview Cottages, and Rathfarnham Mill. These residential areas are situated across the River Dodder from Bushy Park and are considered part of Rathfarnham Village.

Flood Risk in Rathfarnham Village

Rathfarnham Village, a historic suburb of Dublin nestled in a valley, is bordered by the Dublin Mountains to the south and the River Dodder to the west. This unique topography creates a potential for flooding from various sources, including overflowing drains and water running downhill. This article delves into the specific flood risks that Rathfarnham Village faces, focusing on these two primary sources and offering insights into how the community can better understand and mitigate these risks.

Risk of Flooding from Overflowing Drains

The area around Church Lane in Rathfarnham Village lies within Flood Zone B, indicating a moderate risk of flooding (1 in 1000 year flood extents) . Overflowing drains can pose a significant flood risk, especially during periods of heavy rainfall. When the drainage system’s capacity is exceeded, excess water can back up and overflow, potentially inundating streets and properties. This can occur due to several factors:

Blocked drains: Debris such as leaves, litter, and sediment can accumulate in drains, obstructing the flow of water and causing blockages.

Inadequate drainage system capacity: Older drainage systems or those not designed to handle increased urbanization and higher runoff volumes may be overwhelmed during heavy rain.

Poor maintenance: Infrequent cleaning and maintenance of drains can exacerbate the risk of blockages and overflows.
A recent study of flood risks in the area associated with the proposed Bus Corridor Scheme indicates a high risk of pluvial flooding (flooding caused by surface water runoff). However, the study suggests that the drainage improvements planned as part of the scheme will help mitigate this risk . This highlights an important point: while Rathfarnham Village faces flood risks, proactive mitigation efforts can effectively reduce these risks.

In 2000, Woodview Cottages in Rathfarnham experienced flooding due to overflowing drains . This incident serves as a reminder of the potential impact of overflowing drains on residential properties in the village. Furthermore, a resident of Woodview Cottages reported difficulty obtaining flood insurance due to the identified flood risks . This underscores the real-world implications of flood risk, potentially affecting property values and insurance availability.

Risk of Flooding from Water Running Downhill

Rathfarnham Village’s location at the base of the Dublin Mountains makes it particularly susceptible to flooding from water running downhill, especially during periods of intense rainfall . The steep slopes of the mountains can channel rainwater rapidly downwards, increasing the risk of flash floods and surface water runoff. Several factors can exacerbate this risk:

Deforestation and urbanisation: Removing vegetation and increasing impermeable surfaces on the slopes reduces the ground’s ability to absorb water, leading to increased runoff.
Soil type: Soil with poor drainage capacity, such as clay soil, can contribute to surface water runoff.

Steepness of slopes: The steeper the slopes, the faster the water flows downhill, increasing the risk of flooding.
To illustrate the potential impact of water running downhill, consider the phenomenon of lahars, which are volcanic mudflows. While Rathfarnham Village is not in a volcanic region, the principle of water carrying debris downhill during heavy rainfall applies . In this case, the steep slopes of the Dublin Mountains could contribute to the rapid accumulation of water and debris, potentially leading to localized flooding.

It’s important to note that the level of flood risk in Rathfarnham can vary significantly depending on the specific location and proximity to the River Dodder . For example, during Hurricane Charlie in 1986 and the October 2011 flooding events, most of the flooding on Dodder Road affected front gardens, with very few houses experiencing significant inundation.

Climate Change and Flood Risk

Climate change is expected to increase the risk of flooding in many areas, including Rathfarnham Village . More frequent and intense rainfall events, as predicted by climate models, can overwhelm drainage systems and increase surface water runoff. Additionally, rising sea levels can exacerbate flooding in coastal areas and those near rivers with tidal influences.

A Strategic Flood Risk Assessment (SFRA) for Dublin City notes that climate change is likely to increase flood risk, particularly along the coast and tidally dominant river reaches . While Rathfarnham Village is not directly on the coast, it is located near the River Dodder, a tributary of the River Liffey, and could be indirectly affected by rising sea levels and increased river flows.

Historical records provide evidence of the impact of extreme weather events on flooding in the Dublin area. In 1965, overflowing rivers, including the Dodder, Dargle, and Tolka, caused significant flooding in Rathfarnham and other parts of Dublin . Similarly, during Hurricane Charlie in 1986, overflowing drains and small rivers caused widespread flooding in Dublin, highlighting the vulnerability of the city to intense rainfall events .

Types of Flooding
Understanding the different types of flooding can help residents and property owners better assess their risk and take appropriate preventative measures. Here are some common types of flooding relevant to Rathfarnham Village:

Fluvial flooding: Flooding from rivers or streams overflowing their banks. The River Dodder, which flows through Rathfarnham, has a history of flooding, as seen in the 1965 event .
Pluvial flooding: Flooding from surface water runoff, often caused by heavy rainfall exceeding the capacity of drainage systems. This is a significant concern in Rathfarnham, as highlighted in the flood risk assessment for the Bus Corridor Scheme .
Groundwater flooding: Flooding that occurs when the water table rises above ground level. This can be a concern in areas with certain soil types or poor drainage.
Coastal flooding: While Rathfarnham is not directly on the coast, rising sea levels due to climate change could indirectly affect water levels in the River Dodder, potentially increasing the risk of flooding in areas close to the river.

Signs that a Property is at Risk of Flooding

Several signs can indicate that a property in Rathfarnham Village is at risk of flooding:

History of flooding: If the property or surrounding area has experienced flooding in the past, it is more likely to flood again. For example, Woodview Cottages have a history of flooding .
Proximity to water bodies: Properties located near the River Dodder or its tributaries are at higher risk of flooding.
Low-lying areas: Properties in low-lying areas or depressions are more susceptible to flooding, especially from surface water runoff.
Poor drainage: Inadequate drainage systems or signs of waterlogging can indicate a higher flood risk.

Property owners in Rathfarnham Village can take several steps to mitigate the risk of flooding:

Maintain drains – Regularly clean gutters, downpipes, and drains to prevent blockages.
Install flood barriers – Flood barriers can help prevent water from entering a property.
Improve drainage – Install or upgrade drainage systems to handle increased runoff.
Elevate electrical appliances – Raise electrical appliances and wiring above potential flood levels.
Relocate valuables – Store valuable items in a safe place above potential flood levels.
Purchase flood insurance – Flood insurance can provide financial protection in the event of flooding.

Conclusion
Rathfarnham Village faces potential flood risks from overflowing drains and water running downhill, particularly during periods of heavy rainfall. Climate change is likely to exacerbate these risks by increasing the frequency and intensity of extreme weather events. The impact of flood risk extends beyond property damage, potentially affecting property values and insurance availability, as seen in the case of Woodview Cottages .

It is crucial for the Rathfarnham Village community to be aware of these risks and take proactive steps to mitigate them. This includes individual actions such as maintaining drains and installing flood barriers, as well as community-level initiatives to improve drainage infrastructure and raise awareness. Collaboration between residents and local authorities is essential to effectively address the flood risk and protect the village from future flooding events.

Further research and investigation could provide a more detailed understanding of the specific flood risks in different areas of Rathfarnham Village. This could involve detailed flood modeling, mapping of vulnerable areas, and community-based risk assessments. By working together, the community can build resilience and ensure the long-term safety and well-being of Rathfarnham Village.