How to minimise the risk of flooding and lessen flood damage

By on October 9, 2012 in Building Management

How to minimise a facility’s risk of flooding and the ensuing damage to a facility that flooding can cause is shared by TERRANCE BEHAN and PETER WILLSE from XL GAPS.

Water is a powerful force – a force that, if not considered wisely, can become very destructive, as seen in numerous flooding events worldwide. In recent history, floods have not only put buildings and infrastructure underwater; they have virtually stopped business, even thousands of miles away. What can be done to minimise a facility’s risk and the ensuing damage to a facility that flooding can cause?

DETERMINING POTENTIAL DAMAGE
Good planning would suggest that new industrial properties not be built in areas susceptible to a 500-year or more frequent flood recurrence. But that may be easier said than done, especially in some parts of the world.
In the US, flood information is shown on the Flood Insurance Rate Map (FIRM) published by the Federal Emergency Management Agency (FEMA). It is relatively simple to determine site location in relation to the one in 500-flood level, whether it is in a flood-protected zone and relative location of upstream dams, for instance. For most parts of the world, however, including the Asia Pacific, flood-mapping showing the 500-year flood reoccurrence areas is not yet available. Availability of such data is slowly improving, but it is still difficult to determine flood exposure for existing and proposed building sites in many parts of the world.
Fortunately though, skilled engineers can effectively estimate 500-year flood reoccurrence and flood exposure for the site where this information is not available from flood maps. Assuming a log-normal distribution for flood data, this can be done with as little as two flood heights and their recurrence intervals. While a log-normal distribution for flood data is not necessarily accurate, the method is nevertheless a guide in the cases where there is limited data. With a variety of information, it is possible to:

  • determine whether the property or part of the property is subject to a one in 500-year flood or some flood reoccurrence interval less than that
  • determine the potential depth of flooding through buildings for selected scenarios
  • estimate potential flood damage – we would normally use the one in 10-year flood for the normal loss expectancy (NLE) scenario, the one in 100-year flood level for the probable maximum loss (PML) scenario and the 1 in 500 year flood for the maximum foreseeable loss (MFL) scenario
  • provide advice on possible flood mitigation measures, and
  • provide advice on flood pre-emergency plans.

Flood loss estimates will be dependent upon values at risk, the type of building, equipment and stock exposed, and the expected height and speed of water through each building.

MINIMISING POSSIBLE DESTRUCTION
The reality is that buildings have been built in flood prone areas. For these sites there are a variety of preventative measures that a business can take to minimise property damage and financial losses. For one, facilities in flood prone areas should not be without a flood pre-emergency plan, which addresses flood mitigation and salvage. Such a plan includes:

  • protocols to monitor levels of nearby water resources, such as lakes, streams and rivers, and protocols to monitor the level of ice for those areas where the flooding is caused by ice damming
  • inspection of all protection features, such as floodgates, levees and berms
  • ensuring the availability of sand and sandbagging material
  • setting up a working relationship with the fire department to coordinate a response if there is a fire
  • planning who is going to coordinate the relocation of equipment, papers and stock, who is going to survey the protection features during the flood and who has the authority to initiate the plan
  • ensuring the availability of equipment for clean-up operations, including mops, brooms, chainsaws and other tools, and
  • a call-back plan to have employees return to help with the plan prior to the flood and to help clean up after the flood.

In addition to this pre-flood planning, other steps to consider include:

  • providing permanent flood protection barriers, such as, levees, berms, channels or flood walls
  • moving or raising all equipment to above the 500-year flood elevation, especially high-value equipment and electrical panels
  • storing important papers and spare parts above the 500-year flood elevation
  • installing manual shut-off valves on the sewer outlets and floor drains
  • analysing yard storage tanks, silos and large vessels to see if they can become buoyant during a flood, and
  • incorporating flood-related scenarios into the site’s business continuity plans, including loss of or restricted access to the site by employees, and loss of part supplies from flood exposed critical suppliers.

WHAT TO DO WHEN A FLOOD OCCURS
If floodwaters appear inevitable, there are a variety of other steps that can be taken to minimise potential property losses and business interruptions, including:

  • shutting down processes safely and draining open tanks of flammable or combustible liquids
  • bracing unsupported structural members at construction sites
  • updating important back-up records and moving them to a location not vulnerable to flooding
  • anchoring yard items that can be moved by floodwaters, such as trailers, lumber and loose yard storage
  • moving stored materials inside if practical
  • barricading critical outdoor equipment with sandbags to provide protection against floating debris
  • assembling necessary supplies and equipment at a central, secure location, including portable pumps and hose, mops and squeegees, emergency lighting, tarpaulins, lumber and nails, power and manual tools, shovels, axes and sandbags
  • ensuring the on-site emergency crew has non-perishable food, two-way radios, first aid equipment, stored drinking water, lighting, an emergency generator and fire pump fuel tanks, as well as inspected fire protection equipment
  • checking travel brakes on movable cranes and bridges, and anchoring them in accordance with the manufacturer’s out-of-service instructions
  • placing sandbags at vulnerable building openings and around critical outdoor equipment, and trying to divert water from critical areas such as holes in foundations, doorways and sills
  • moving important machinery, stock and reports to higher elevations – by knowing the past flooding history of the area reasonably safe areas can be selected – and, if major equipment cannot be moved, coating vulnerable metal surfaces with grease
  • shutting off all flammable and combustible liquids and gases lines at their source to prevent the discharge of such liquids and gases from piping broken by floating debris, and supporting exposed piping properly
  • making sure above and belowground tanks are properly anchored to prevent flotation, filling empty tanks with water or product, and extending vent lines on active tanks above the anticipated maximum water level
  • lashing down portable containers of flammable or combustible liquids, and
  • shutting off electrical power at the main building disconnection if the building is in imminent danger of flooding.

BE WARY OF WATER LEVEL RISKS
By conducting a flood analysis, loss prevention specialists can prove to be valuable resources to determine where a business’ flood risks lie. More importantly, they can help establish the right protocols and implement preventative measures to minimise potential losses from flooding.
Given the unprecedented flooding, property damage and business interruption that occurred last year, facility managers will be wise to be wary of their facility’s potential water level risks and raise their level of risk management protection.

Terrence Behan heads up the Asia Pacific region and Peter Willse is the director of research for XL GAPS. XL GAPS, part of XL Group, provides property loss prevention consulting and delivers individually tailored solutions to protect and enhance property, production and profit. 

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