Stormwater Issues

Damage Caused by Routing Construction Runoff through a Permanent Swale
Courtesy DCC ©

First settlements in Ireland originally conveyed runoff to the nearest stream of river. Later it was understood that stormwater runoff polluted rivers and had a significant effect on biodiversity and water quality. These types of pollutants can include oil, antifreeze, litter, decomposing organic materials and animal wastes. This problem is exacerbated by poor drainage systems in Ireland. Only retention ponds and stormwater wetlands have sufficient retention time to allow for breakdown of many pollutants.

Stormwater overflow is caused by numerous issues including:

•  Barriers to the adoption of solution based policies are present (i.e. SuDs) due to lacking leadership and regulations governing the management of stormwater discharges.

• A lack of sustainable drainage in Ireland persists with the majority of urban areas being drained by combined sewer systems. This means that wastewater and stormwater are conveyed to a single pipe. Heavy rainfall events often result in the exceedance of the capacity of such pipes. This can result in untreated discharges reaching rivers and other natural water sources via storm water overflows (SWOs). SWOs are a source of microbial pathogens and can affect human health (EPA, 2018).

• Changing weather patterns due to climate change will pose significant stress on drainage systems in Ireland as it is projected that the country's number of heavy rainfall days per year may increase. Such weather events can lead to an increase in both fluvial and pluvial urban stormwater flood risk (OPW, 2015).