Ponding (Drainage) Flooding

Primary reference(s)

WMO, 2021. Technical Regulations Volume III: Hydrology. WMO-No. 49. Page IX. World Meteorological Organization (WMO). Technical Regulations, Volume III – Hydrology Technical Regulations, Volume III – Hydrology. Accessed 15 May 2025.

Annotations

Key relevant UN convention / multilateral treaty

Sendai Framework for Disaster Risk Reduction 2015-2030.

Drivers

Ponding flooding, also known as waterlogging, is primarily driven by a combination of intense or prolonged rainfall that exceeds both the soil’s infiltration capacity and the limits of urban drainage infrastructure. In cities, the widespread replacement of permeable land with impervious surfaces such as asphalt and concrete significantly increases surface runoff, leading to rapid accumulation of water during storms (Environment Agency, 2011). This effect is particularly severe in topographic depressions—natural or human-made—where water tends to collect, including in areas of land subsidence or reclaimed terrain. Inadequate or ageing drainage systems, often designed using outdated precipitation data, struggle to cope with current rainfall extremes and are prone to failure (UN-Habitat, 2020). Additionally, human-induced changes such as wetland loss, which eliminates natural water retention, and modifications to landforms from agriculture or construction can disrupt historical drainage pathways and increase vulnerability (BGS, 2023). These drivers, taken together, contribute to the rising incidence and severity of ponding flooding, particularly in rapidly urbanising regions. 

Impacts

Floods are one of the most common hazards. Similar to groundwater flooding, and notwithstanding the general impacts of flooding provided in the chapeau, due to their usually slow onset, ponding flood’s main health effects are related to water-borne and vector-borne diseases. 

The effects of flooding on health are extensive and significant, ranging from mortality and injuries resulting from trauma and drowning to infectious diseases and mental health problems (acute and long- term). While some of these outcomes are relatively easy to track, ascertaining the human impact of floods is still weak. For example, it has been reported that two-thirds of deaths associated with flooding are from drowning, with the other third from physical trauma, heart attacks, electrocution, carbon monoxide poisoning and fire. Often, only immediate traumatic deaths from flooding are recorded (WHO, 2013). 

Morbidity associated with floods is usually due to injuries, infections, chemical hazards and mental health effects (acute as well as delayed) (WHO, 2013). Hypothermia may also be a problem, particularly in children, if trapped in floodwaters for lengthy periods (WHO, no date). There may also be an increased risk of respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain). Power cuts related to floods may disrupt water treatment and supply plants, thereby increasing the risk of water-borne diseases as well as affecting the proper functioning of health facilities, including cold chain (WHO, no date). Floods can potentially increase the transmission of the following communicable diseases: water-borne diseases (such as typhoid fever, cholera, leptospirosis and hepatitis A) and vector-borne diseases (such as malaria, dengue and dengue haemorrhagic fever, yellow fever, and West Nile Fever) (WHO, no date). 

The longer-term health effects associated with a flood are less easily identified. They include effects due to displacement, destruction of homes, delayed recovery and water shortages (WHO, 2013).

Multi-hazard context

The figure below summarises common interactions between ponding flooding and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.

Multi-hazard diagram

Risk Management

No Information Available

Monitoring

The section above and the table below offer an overview of monitoring ponding flooding. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management.