But the wet stuff was coming. We could have called it 'Flooding Floyd.' Lumbering northward up an already soggy eastern seaboard, it dumped a swath of unrelenting downpours from South Carolina to Maine.
Rivers rising and water pouring into homes and businesses became a common news image in areas hardest hit. Few were prepared for flooding exceeding record levels. The table below shows which U.S. states were most affected by the storm.
Of the damage costs to FM Global's customers' properties, flooding alone caused 83%; wind, 13%; and service interruption, 4%.
And, yes, the flood threat may get worse. Yet, its effects in 2000 and beyond will probably depend as much upon people's actions as the events themselves. 'Floyd reminded us of two realities people often overlook when it comes to flood-response planning,' said Bill Kennedy, FM Global's corporate flood coordinator.
- One - flood level predictions are often ignored, underestimated or taken too literally. Potential results? People do not realize the real exposure to their site and normal operations, and are not adequately prepared when the flood does occur. How many times have you heard the following statement in media coverage: 'We just didn't realize a flood would hit us or be this bad'?
- Two - as in other parts of the world, land areas along many U.S. streams are significantly different than they were 20 to 30 years ago when many of the flood maps were developed. As land is developed and the characteristics of watersheds change, streams may rise faster and higher now than they did historically. As land is cleared for buildings, parking lots or other development, rainwater, which was once absorbed by the forested ground, now runs off quickly into the lakes and streams. Flood emergency planning often lags behind subtle, but critical, changes in the level of exposure.'
What is a recurrence level and why should you be concerned?
ver half the damage costs from Floyd resulted from flooding that exceeded levels projected for a 500-year recurrence interval (return period). Many people erroneously assume that the 100-year flood means you'll get a flood of this size every 100 years and, once it occurs, it will not occur again for another 100 years. Not true. Statistically, the 100-year flood has a 1% chance of happening one or more times in a given year. A 50-year flood is twice as likely to occur in any year as a 100-year event. A less frequent but more devastating 500-year or larger flood has a 0.2% chance of happening in a year.
Translation? You can get the 50-, 100-, or 500-year flood several times in a few years. Or, the flood can exceed record levels and statistical projections. No matter what the flood maps show, you never know exactly how high the river will rise - until it does. So building a floodwall or other permanent protection to an exact flood level prediction for your property is shortsighted. If you're smart, you'll add 'freeboard' to levees and floodwalls - a safety allowance of a few feet (one meter) higher than flood predictions or design heights.
And even if your facility isn't in a flood zone, don't count on being safe on dry ground. Flooded roads could keep you too far away from your property to prevent further damage that often worsens by the minute after the flood has gone.
In addition, as a river or its watershed characteristics change, the true probability of a major flood might be even greater than the predicted event. Flood preparedness is much more than having a flood map in hand. Your ground and basement floor elevations must be accurately measured and the flood exposure calculations must account for any watershed or ground changes that may have occurred over the past few years.
Let's learn from Floyd's victims
Companies that suffered losses often made four major mistakes prior to Floyd:
- Using U.S. Federal Emergency Management Agency (FEMA) flood maps to identify exposures. These maps had limitations and relied upon out-of-date factors like old river flow data and inaccurate ground level surveys. You need recent data, not 30-year-old maps.
- Not having a thorough Flood Emergency Response Plan (FERP) with a well-trained Flood Emergency Organization (FEO). The end of this article gives you a roadmap for creating a new FERP or updating an existing one.
- Not using the 500-year recurrence flood level to determine the impact you can expect. (The sidebar article titled Statistical Basis for Zones, page 78, cites several reasons why.)
- The lack of ingress and egress to their plants due to road flooding was not considered.
Ask yourself about
1. Basement elevation - has it been accurately quantified using the latest technology?
2. Rivers and streams near your property line - how close are they to the property line? If they all flooded at once, what could result?
3. Basement pumps - will they be able to pump out seepage, even during severe downpours and all local streams cresting?
4. Potential response of sewer lines during flooding - could any break from pressure created by cresting rivers? Are they adequately designed to remove heavy rainfall from your facility and/or the surrounding area?
5. Method used to determine ground elevations and potential flood levels - has it been developed recently? If possible, can it be verified quantitatively?
6. Location of your property in relation to a given 500-year flood zone - is the flood evaluation based upon the exact location of your buildings rather than an analysis of the general area? Flood elevations may differ significantly even on a small property.
7. Flood duration potential and its impact on utilities and access - could a flood impact power, water, waste treatment or telephone utilities, block access to the property or prevent key people from getting in or out?
8. Reliability of source data like floor elevations, historic flood levels, and existing flood maps - are they current and based on existing hydrologic features of the property and surrounding area?
9. Potential for bridge clogging or debris in a flooding river - how much could major blockages increase the flood elevation at your site?
10. Flood protection - are fixed protection safeguards like levees designed for the 500-year event and well maintained?
11. Drainage systems - have you periodically cleaned catch basins and inspected drainage pipes for clogging? Are drainage swales free of vegetation and debris?
12. Drainage - are roof drains adequate, inspected frequently (especially before and after a storm), and all debris removed in and around drains to prevent clogging?
13. Freeboard - is this included in the flood evaluation? (Freeboard is height added to your floodwall or levee above the expected flooding elevation for your exact property location.)
14. Equipment exposure - might critical equipment be vulnerable to flooding levels exceeding any on record?
15. Disaster recovery plan - has it been updated to reflect a recent flood evaluation?
A smart FERP
A good plan is well-conceived, thorough and
- developed with participation from all portions of the operation
- includes input from outside agencies
- is documented and distributed to key participants
- is exercised and updated regularly
Months ahead of flooding season
A step-by-step FERP specifies responses for all potential flood scenarios and cites educational goals of the training program for the FEO. The formal plan sets up procedures for
moving critical equipment and susceptible commodities to safe areas, i.e., higher ground
prelubricating and covering susceptible equipment
- deciding work hours and number of personnel needed to do the work
- obtaining supplies for pre-flood preparation and post-flood recovery: pumps, generators, emergency lighting sandbags, tarpaulins, cleaning supplies - and making sure all equipment is in good condition and proper working order
- assigning security and surveillance responsibilities
- monitoring weather forecasts
- monitoring web sites such as the U.S. National Weather Service's River Forecasting Center
- prioritizing salvage and cleanup activities
- accessing names, addresses, phone and fax numbers and e-mail addresses of vendors that supply salvage services
- providing temporary water, power, heat or refrigeration, and other services
- working with cities and/or local government to ensure that nearby streams are kept free of debris, brush and trees cut back, and bridges kept clean to ensure a free flow of water through culverts and under bridges
Training includes instruction about all exposures and makes employees responsible for being completely familiar with the flood plan. Employees should be trained (and practice) to respond to all emergency scenarios identified in your plan. Training will enable them to
- recognize early signs that a potential flood event is developing
- recognize changes on the property that could impact flooding
- know how to install flood doors, flood windows and essential barriers
- provide proper means to elevate property or move it to higher ground
- respond more effectively to unforeseen events during a flood
Be aware of long-term weather predictions. Will snowpack be heavier than usual this year? Have local land elevations changed? Have you made any construction changes to the property that might have increased susceptibility to flood?
Check flood protection equipment and make sure it operates properly. Stockpile supplies for building temporary dikes, levees or flood walls. Identify the need for protective coverings such as tarps.
Identify equipment that is buoyant, movable and will need anchoring. Check key items that cannot be elevated or moved to higher ground. Provide spot flood protection procedures for individual pieces of equipment.
When flooding threatens your site
Provide employees with step-by-step response procedures to flood warnings. Monitor early flood advisories and prepare equipment, supplies and personnel. As applicable, check river stages periodically with the government agency that has this information. If you're located in a coastal area, pay close attention to the path of tropical storms and other very severe weather.
Temporary protection and precautions:
- Install flood barricades, doors, and windows and other temporary, flood-related protection equipment.
- Check all access roads. Which are most likely to flood? Are there alternate routes for employees? Can any roads on your property be built up to ensure access?
- Build temporary levees
Prioritize your response whe every minute might count!
You may have 500 things to do when preparing for a predicted flood event. Which come first?
Bill Kennedy advised, 'Although you might not be able to eliminate all damage at some facilities, your goal should be to minimize the impact to critical buildings, equipment and functions. You want to return the facility to normal operations as quickly as possible. Typically, a flood warning permits only time enough for a few of them.
'I suggest that you list 40 or 50 action items to complete first - the ones that could best minimize the extent of damage and downtime. Decide who will take these actions and how they will be done. After mandating the most critical, make sure the plan addresses other needs on a priority basis and as time permits. It is inevitable that unanticipated challenges will be encountered during and after a flood. A FERP that establishes the most critical issues and prioritizes loss mitigation steps puts management in a much better position to deal with the surprises and reduce the adverse consequences,' added Mr. Kennedy.
During the flood
Activate emergency response and coordinate with agencies offering outside assistance, repairs, salvage and business resumption plans.
The emergency response team begins:
- monitoring potential flood damage (no access to property, interrupted fire protection, utility outage, shutdown, etc.)
- securing outside equipment
- checking utility backup and fire protection equipment
- organizing cleanup supplies
- setting up emergency communication equipment in event of total utility loss
- relocating critical equipment to temporary storage areas
After the flood
The more thoroughly you carry out a well-conceived plan, the less the flood impact will be. The faster you perform salvage, the sooner you'll be back in business. The sooner you restore fire protection and alarm services, the less chance you have for a catastrophic fire during cleanup and repair work.
Check all fire protection control valves to make sure they are open and, if not, check for broken or disconnected piping before reopening the valves. A salvage crew should act quickly after flooding subsides to
- remove water and silt
- weather proof damaged buildings
- thoroughly clean and dry vital equipment
- dehumidify damp areas
- lubricate and cover susceptible equipment to reduce rust and corrosion
- preserve equipment and materials that might otherwise be lost
Debrief personnel after the flood. What worked? What didn't? Revise the plan or retrain if needed. Restock emergency supplies. Prioritize improvements.
The following side bar article, Statistical Basis for Zones, is an example of Scheffler's latest research on flooding.
Statistical Basis for Zones
The flood discharges derived under the Flood Emergency Management Agency (FEMA) are averages. The discharge will be equaled or exceeded 50% of the time for the given flood events. Since flood stage increases with flood discharge, the flood stage also will mean 'average' value that is equaled or exceeded 50% of the time for this event.
Implication? A higher flood stage than shown on a Flood Insurance Rate Map (FIRM) could occur for a given return period 50% of the time (Upper Confidence Limit on Fig. 1).
This confidence band or uncertainty around the discharge flow rates translates into uncertainty around the extent of flooding as shown below on the cross section A-A' (Fig. 2) and plan view of the flood plain (Fig. 3).
Key points
- Typical flood studies provide 50th percentile flood elevations and, as a result, the elevations could actually be higher for a given return period.
- A difference of 1 or 2 ft (0.3 or 0.61m) may not necessarily mean you are out of a flood zone.
- If a flood map tells you roughly that you're in a 100- or 500-year zone, you can be pretty sure you are. If it says you're out, don't be so sure.
Figure 2
Figure 2
'2000 Factory Mutual Insurance Company. Edited and reprinted with permission. From RECORD, Volume 77, No. 1.
