To help you advise your clients on how best to manage their flood exposures, itï¿½s important to understand the different types of flooding.
2013 was one of the more active flood years in recent memory and headlines around the world seemed to reinforce the severity. In Central Europe, extreme flooding began in late May and ran into the summer months, causing approximately US$3.9 billion in insured losses. Similarly, heavy rainfall in June caused waters to quickly rise in Alberta, Canada, forcing evacuations in numerous communities. Total damage estimates exceeded US$1.7 billion, making it the costliest disaster in Canadian history.
In the United States, heavy rain in Colorado resulted in catastrophic flooding in the northern and central parts of the state. While it was an especially active year in terms of flooding, in our experience, flood is the second largest driver of loss. Over the past 30 years the United States has averaged US$7.82 billion in annual flood losses.
To help you advise your clients on how best to manage their flood exposures, it’s important to understand the different types of flooding, flood hazard categories and how to mitigate flood loss.
Types of Flooding
In the simplest terms, flooding occurs when natural water leaves its normal boundaries and flows into areas not normally covered by water. Severe flooding is caused by major weather and geological events. The three common types of flooding are: riverine, storm water and coastal.
Riverine flooding occurs along rivers and tributaries. Heavy rains over an extended period of time or rapid snowmelt can saturate the ground and induce runoff that exceeds the capacity of local rivers, creeks and natural surroundings. These scenarios cause river water to overflow and spill out into adjacent low-lying areas. This type of rainfall influences flooding. For example, steady rain from a tropical storm over an extended period of time can cover a large area which affects many rivers, creeks and lakes—leading to more significant flood damage.
Storm water flooding occurs when heavy rainfall and/or snowmelt collects in a localized area before the runoff reaches a body of water or channel where water normally resides. This typically occurs due to poor drainage, landscaping, overdevelopment or inappropriate building design.
Coastal flooding occurs along coastlines, inland bays, rivers and tributaries. An approaching tropical storm raises the sea level due to its low-pressure center and high winds that can extend for hundreds of miles. When a tropical storm makes landfall, this abnormal rise in sea level comes ashore as large waves. Ocean water brought ashore by the waves will seek the lowest levels along the coastline and drive inland. The storm surge lasts for a relatively short period (four to eight hours) but can add significant amounts of salinity to the flooded estuaries and inland areas—which can result in higher damageability percentages.
Another cause of coastal flooding is a large displacement of ocean water created by an undersea earthquake or volcano eruption, referred to as a tsunami. Because of their potential size, tsunamis can affect an entire ocean basin.
Flood Hazard Categories
At Affiliated FM, our account teams utilize local flood resources to classify flood exposure into three main categories: high, moderate and low. They evaluate flood exposure in the United States using our state-of-the-art geographic information systems (GIS) to overlay flood zone and levee information on top of satellite images of client locations.
In addition, flood data is available in the United States to identify “high hazard flood zones,” which are geographic areas that have been flooded in the past, or are predicted to flood in the future. History shows that approximately 80 percent of all flood loss occurs within the high or moderate hazard zones. These flood zones are categorized as follows:
|High – A or V zones
||Area exposed to a 1-percent annual chance of flooding.
|Moderate – B or X (shaded) zones
||Area exposed to a 0.2-percent annual chance of flooding.
|Low – C or X (unshaded) zones
||Area not exposed to 1-percent or .2-percent annual chance flooding.
Outside the United States, GIS and local engineering resources are used to evaluate flood exposure. In cases where no flood information is available or the proximity to a flood exposure makes determination imprecise, FM Global Field Engineers can visit your client’s site with precision surveying equipment to accurately quantify site details and specify flood exposure.
While flood is one of the most costly natural hazards in the world, at Affiliated FM we believe your clients don’t have to be vulnerable to flood loss and can take proactive steps to prevent or mitigate flood damage.
Some low-cost and effective physical protection schemes include adding additional curbing to redirect water away from key buildings and building openings. You also can advise your clients to relocate high-value items, such as stock, supplies and important records or plans to buildings that are not exposed to flood.
Additionally, implementing a Flood Emergency Response Plan (FERP) can have a tremendous impact on mitigating food loss to your client’s business. A FERP is a documented plan of actions a client will take when flood is imminent.
For a specific analysis of your client’s potential flood exposure, contact your Affiliated FM Account Engineer. Using available flood, rainfall and topological data, in addition to local knowledge, we can provide specific, practical steps your clients can take to help avoid a flood loss.
For more information, visit www.AffiliatedFM.com/nathaz to download helpful flood resources, or contact your Account Engineer.