Impact of floods, hurricanes and storms

What happens to the water network in the wake of hurricanes and floods?

Just days after Hurricane Harvey dumped over 50 inches of rain on the American state of Texas causing the deaths of 60 people and delivering billions of dollars worth of damage to homes and property, Hurricane Irma has wreaked havoc in the Caribbean with the most powerful Atlantic storm in recorded history.

Hurricanes are the atmosphere’s attempt to move heat from the warm equatorial regions toward the cold polar regions. They are large, swirling storms and can produce winds of 75mph or more. Formed over warm ocean waters, if a hurricane reaches land it can push a wall of seawater ashore and cause a storm surge. It’s not unusual for the heavy rain and storm surge from a hurricane to result in flooding.

But what impact do hurricanes and storms and the consequent flooding they produce have on a country’s infrastructure and its wastewater network? We caught up with Flood Risk Manager, Chris Walker  to find out more.

“The impact on critical infrastructure is described in one of two ways: bad or catastrophic and the actual force of flooding and water rise created will determine the category the impact falls under.

“There are a variety of measures that can be implemented in the event of a hurricane or severe storm to try and lessen its impact. In high flood situations, for example, reservoirs will be drained to make room for any surface water run off from hills and high ground areas. This tactic helps to restrict the amount of water cascading through towns, cities and rural areas where people, homes and properties are most at risk.

“At the same time, the Environment Agency can order water companies to turn off any infrastructure, such as a pumping station or sewage treatment works, that may become damaged due to flood water. This will undoubtedly have been the case with both Hurricanes Harvey and Irma.

“When an area floods, the first impact is that the clean water and treated water can become contaminated. Pumping contaminated water to households could have unimaginable consequences, especially if the house is cut off from the outside world. The temptation to help yourself to drink of water from the tap would be irresistible and potentially life threatening.

“When clean water and waste water are mixed there is a time window of approximately 24 hours before the first level of bacteria turns nasty. 72 hours into a flood situation, there is potential for a huge contamination problem as the water has still not been treated because the infrastructure remains in shut down: clean water is mixing freely with waste and run off water and bacteria is now thriving. During this time, contaminated water can also seep into water pipes making the water already in the pipes non-potable. It is for this very reason that aid requests of bottled water are always made in a flood situation, irrespective of global location.

“Here in the UK, organisations and businesses from National Grid UK and BT to water companies and council have emergency procedures in place to deal with major storm events and consequent flooding. For instance, Skegness and many other coastal areas have fully signposted Evacuation Routes or ‘ERs’. If a tidal surge is imminent and evacuation is required, those living and working in the area are ordered by the authorities to follow the ER routes to safe places. These are usually football stadiums, hospitals and even churches.

“Pre-planning for such events includes the identification of high-grounded areas in which safe refuge can be sought as well as regular crisis scenario training for emergency services personnel, coastguard, water company site crews etc.

“Over recent years the UK has suffered several devastating floods and many important lessons have been learnt. Major changes and improvements have been made in many areas in an attempt to prevent or lessen the consequences of flooding if it occurs.

“For example, when parts of Yorkshire were hit by flooding in 2015, the Yorkshire ambulance service lost communications after hundreds of the green communications cabinets you see on UK streets were flooded, cutting airwaves, signal and all forms of communication. Named the ‘Black Hour’ the ambulance service literally had no means of communication and was unable to effectively co-ordinate its operation.

“As a result, BT, the company that owns and manages those green communications cabinets, installed watertight boxes across the nation in their place. So, when you see a BT operative working on one of those cabinets remember that it is actually watertight and, once shut, the seal cannot be penetrated by floodwater thus ensuring the airwaves remain open in the event of a flood.”