Overland Flooding

Keeping Commercial Properties Safe When Water Rises

The widespread damage in New England in 2012 from Hurricane Sandy serves as a good example of the disruptive and destructive power of overland flooding. Hurricanes, snowmelt, torrential rain, and tropical storms are just some of the many causes of overland floods. Such an event can be disastrous to a commercial property that is not prepared to respond quickly and properly. This guide will provide advice for commercial property managers to prepare for and respond to such overland flooding events.

The What, How and Why of Overland Floods

Overland flooding is defined as a situation in which water rises and covers ordinarily dry land. Some causes include

  • A river overflowing its banks
  • A storm surge from a hurricane
  • A substantial amount of runoff from snowmelt
  • Mechanical failure of a dam or levee

It is important to note that overland flooding is considered a separate problem from other causes of water damage, such as burst pipes or drain backups. This difference is especially important when it comes to insurance coverage.

Generally, overland floods will occur more often when the ground is still frozen or already saturated, such as during the springtime. However, as weather patterns continue to change, these floods are becoming more likely throughout the year.

Within the category of overland flooding, there are two important sub-categories: flash floods and areal floods.

Flash Floods

In a flash flood, water rises or accumulates in a matter of minutes or hours. Causes of flash floods include:

  • Strong storms
  • Torrential rains
  • Mechanical failures such as dams or levees bursting

A sudden, large volume of water travels over dry ground, carrying any contaminants or hazards that it may sweep up. There is little or no time to prepare a property for the oncoming water, and the primary focus is on damage mitigation and recovery.

Areal Floods

An areal flood occurs when rivers, lakes or retaining ponds overflow their banks due to a gradual increase in water volume. Unlike flash floods, areal floods happen more slowly and in stages. The water volume may increase with snowmelt during a spring thaw or in a particularly rainy season. As with a flash flood, areal floodwaters can contain harmful bacteria and other contaminants.

Municipalities and weather services usually provide areal flood warnings and updates on flood stages, allowing nearby property owners to take measures to protect their buildings and material goods.

High-Risk Areas

Any location within a floodplain is at a higher risk of overland flooding. While “floodplain” is defined as “an area of flat land beside a river that regularly becomes flooded when there is too much water in the river,” for insurance purposes this term may also refer to any area susceptible to floodwaters from any source, not just rivers.

Whether a property is located within a floodplain or not, property owners explore flood insurance options to ensure coverage in case of a flood loss.

Other areas susceptible to overland flooding include:

  • Coastal regions
  • Land near lakes, retaining ponds, and other bodies of water
  • Areas that experience heavy seasonal rains
  • Areas prone to frequent freeze-thaw cycles
  • Low-lying areas, including those below sea level

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What’s in Flood Water?

To put it simply, overland floodwater is dangerous, falling into the third category of water damage. The categories are based on the source of the water and the potential for harm that it carries.

  1. Category 1: This is water that has come from a source such as the clean water supply in a home. If addressed within 24-48 hours, most Category 1 water poses a low health risk. However, even clean water can begin to cause mold in as little as 48 hours.
  2. Category 2: This category is known as “gray water.” This water comes from sources that could have mild to severe contamination, including chemicals from fire-suppression systems, treated cooling water lines and discharge from equipment. Caution should be exercised around Category 2 water. Materials exposed to Category 2 water may not be salvageable.
  3. Category 3: “Black water” is highly contaminated, dangerous water that carries a significant risk of disease, infection and irreparable damage. Sources of black water include sewers, drain backups, and water that has overflowed from rivers, lakes or the sea. Extreme caution should be exercised around Category 3 water. Most materials exposed to Category 3 damage will likely need to be replaced.

All overland flood water is considered Category 3 water, due to the likelihood that it has picked up chemical contaminants, bacteria, parasites, viruses and other toxic materials.

Floods’ Effect on Businesses

Overland floods can cause significant damage, disruption and expense for any commercial property. Understanding the potential for these risks can help a property owner prepare their building and make for a faster, more affordable recovery.

Water Damage

The primary concern is damage to building materials, furniture, important documents and electronics. Because overland flood water is considered Category 3 water, anything exposed to it is potentially unsalvageable. Water damage to floors, carpets and drywall can be difficult and costly to repair.

Utility Disruptions

In the aftermath of a flood, utilities may be disrupted locally or for a wide area. Electrical service in the area may be unavailable due to damage to the power grid, or it may be temporarily shut off locally to avoid the risk of electric shock. The water supply may also be disrupted due to contamination or damage to pumping and treatment facilities.


One of the biggest concerns for a business is the potential for extended downtime. Remediation of serious water damage can require closure of some areas or even entire buildings, meaning an inability to conduct business and a loss of revenue. Combined with the potential costs of repairs, this downtime can represent a significant impact to the bottom line of a business.

Preparing for Floods

Floods can be sudden and unpredictable. That’s why it is important for a property owner to be prepared to respond quickly. In fact, insurance claims may be denied if it can be demonstrated that a property owner failed to mitigate the potential damage by taking preventative actions. In the case of flash flooding, there may be no warning ahead of the flood event. For areal flooding events, some steps can help limit potential water damage.

Make a Plan

Every business should have an emergency response plan in place. This plan can help prepare staff to respond to a variety of emergencies. A trusted restoration services partner can help to create such a plan. Essential components of a business emergency response plan include:

  • Primary points of contact for each property
  • Contact information for relevant utilities and vendors
  • Insurance policy information and point of contact
  • Contact information for a trusted restoration services partner such as First Onsite
  • A contact list for all building employees to be alerted in case of dangerous conditions
  • Locations and instructions for utility shutoffs (water shutoff valves and electrical breakers) within the building.
  • Locations and instructions for sump pumps and other important mitigation equipment.
  • Instructions for evacuating the building, if necessary, along with evacuation routes.

Conduct Regular Inspections

Identify and address potential areas of risk before an emergency arises. One of the most important tasks is to remedy deferred maintenance items such as window, roof, HVAC, and plumbing repairs. While these tasks may require some time and investment on the front end, they can potentially save millions compared with the cost of water damage and mold remediation. Among other things, regular building inspections should include:

  • Roof inspection – How old is the roof? Are there missing shingles? Are there flat spots? Are roof drains clear of debris and functioning correctly? Are the gutters clear and in good condition?
  • Building envelope – Are the building’s windows properly glazed and sealed? Are doors sealed and weatherproofed? Are gaps around HVAC units and vents properly sealed?
  • Exterior grading and landscaping – Is the ground around the building graded away from the walls and foundation? Are there low spots in the sidewalk, parking lot or other paved areas that collect water when it rains?
  • Exterior drainage – Are the gutter downspouts properly directing water away from the building? Are storm drains, sewers and catch basins clear of debris?
  • Flood mitigation systems – Are the building’s sump pumps working? If the building has flood gates, are they in good working order?

Create an Emergency Kit

Each building should have an emergency kit. According to Ready.gov, an emergency kit should contain, at minimum:

  • Large containers of clean water
  • Several days’ worth of non-perishable food
  • A first aid kit
  • A battery-powered radio

Find a Trusted Recovery Partner

An experienced recovery partner like First Onsite can help a business prepare its emergency response plan, address areas of risk and concern before a loss occurs and provide end-to-end assistance with handling a loss event. Proactively addressing potential issues can help limit the amount of damage and expense caused by a flood.

Final Preparations

If an overland flood is imminent, additional steps can be taken to help protect the property. Documenting these mitigation steps is also a good idea, as a “failure to mitigate damage” is a potential reason for an insurance company to deny flood damage claims. These mitigation steps may include:

  • Filling and stacking sandbags to hold back flood water
  • Putting flood gates in place
  • Boarding up doors and windows
  • Moving electronics, important documents and other valuable items to higher floors

After the Flood

If an overland flood occurs, it is vital for a business to respond quickly to keep people safe, mitigate water damage and begin the recovery process. Even clean water can begin producing mold in as little as 48 hours, and Category 3 overland flood water presents an even more significant health and safety risk.

Safety First

After a flood, first ensure the safety of all employees, tenants and other individuals who may be in and around the building.

Employees should be contacted and told to avoid the area until it can be made safe. Electrical breakers should be turned off before entering any flooded area to avoid electrical shock. If the breakers are inaccessible due to floodwater, it is best to call the electric company or another professional.

Wet areas may also be slippery, especially in winter when there is potential for flood water to freeze. Category 3 flood waters are likely to contain a variety of harmful contaminants, so all individuals should wear proper PPE to protect from infection and disease.

Call a Recovery Partner

For businesses that have not partnered with a recovery provider like First Onsite in advance, time is of the essence in finding an experienced, trustworthy company to aid with navigating the mitigation, recovery and insurance claims processes. In the event of an area-wide event or loss, these service providers will be in high demand, and finding a partner that can provide reliable, trustworthy end-to-end recovery solutions may be difficult.

Contact the Insurance Company

Contacting the insurance company as soon as possible after a loss is key. Insurance policy holders are obligated to notify their insurance company of a loss, and often are required to provide notification within a specific time frame. Notifying the insurance company does not necessarily mean filing a claim and facing increased deductibles, despite the common misconception that it does. Notifying the insurance company simply allows it to do its due diligence in responding to the loss, and does not necessarily mean filing a claim.

Document Everything

As part of the insurance process, it is important to document as much as possible with photos and video. This documentation will help to establish the details of the loss and provide the insurance company with as much information as possible for processing any claims made. A good rule to follow for this process is to always err on the side of too much documentation.

Remove “Free Water”

The first step in mitigating damage after a flood is removing “free” or standing water. For a small volume, direct standing water toward drains with a mop or squeegee may be sufficient. For moderate volumes, a wet/dry shop vacuum can be useful. Larger volumes may necessitate the use of a pump system. For removing large amounts of standing water, it is advisable to contact a professional.

Dry the Site

The most important thing after a flood is to thoroughly dry all affected materials. Mold can begin to form after as little as 48 hours. The most important elements of drying an affected site are continuous movement of air and maintaining a low moisture level. Provided they are safe to operate, air conditioning systems can provide dehumidification and keep air moving through the space to facilitate drying.

Rugs, carpets, and carpet pads should be lifted to allow airflow under and around the dampened materials. Large pieces of furniture may also be moved or lifted to allow for better airflow. Drying walls and ceilings may require the opening of “weep holes” to drain water trapped within enclosed spaces. Moldings and non-permeable wall coverings will need to be removed to allow wet drywall and other building materials to dry.

Begin Cleanup & Repair

Because overland flood water is Category 3 water, many of the materials exposed will need to be removed and replaced. These materials could include flooring, carpeting, furniture, documents, and building materials. Damaged drywall may require what is known as a “flood cut,” or the removal of the lowest 2-4 feet of material to allow for the removal of wet insulation, drying of the wall cavity and replacement of contaminated materials.


Don’t Do It Alone

Overland floods can cause significant damage and contribute to potential long-term health and safety risks. Rather than attempt to navigate the recovery process alone, property owners should find a trusted recovery services provider such as First Onsite, which can provide end-to-end solutions, simplify the recovery and speed up the process of getting back to “business as usual.”

Ready.gov – Floods: https://www.ready.gov/floods
Ready.gov – Build a Kit: https://www.ready.gov/kit
FEMA.gov – National Flood Insurance Program Terminology Index: https://www.fema.gov/flood-insurance/terminology-index
Oxford English Dictionary – “flood plain”: https://www.oxfordlearnersdictionaries.com/us/definition/american_english/flood-plain

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