Flood Risk

When the Rain Came

A year ago, parts of Colorado were besieged by a 1,000-year flood event leading to more than $2 billion in economic damages.
By: | September 2, 2014

Colorado is not a state that is normally associated with floods. It’s literally one of the highest states in America, with plains in the east that rise up into the Rocky Mountains in the west. It can be arid. It’s seen droughts. But one year ago that all changed. The floods came.

The rain started falling on the mountains of the Front Range on Sept. 9, 2013. The state had had a summer of drought that year, so some probably welcomed the rain.

But the rain kept falling. And got heavier. And by Sept. 15, the resulting floods had resulted in 18 counties being covered by federal emergency declarations, as emergency services personnel mobilized to deal with the disaster.

Deb Darnofall, risk manager. City of Longmont, Colo.

Deb Darnofall, risk manager. City of Longmont, Colo.

Deb Darnofall, risk manager for the City of Longmont in northeast Colorado, told Risk & Insurance® that the rain was “biblical” in its scope and extent.

“It started raining on Sept. 9 with 15 to 25 inches of water dumping over 200 miles of land north to south in a week. I had seen concentrated areas of rain in the past, but never the breadth and duration of the September storm,” said Darnofall.

“When I received the call to respond to the Emergency Operations Center at 3 a.m. on Sept. 12, my heart sank, but simultaneously my adrenaline kicked in.”

The rain was caused by a confluence of events. “Moist air was drawn up from the Gulf of Mexico and combined with a low-pressure system and a cold front over Utah,” said Joseph Becker, scientist at catastrophe modeling firm AIR Worldwide. “The area’s mountainous topography caused air to cool as it moved upslope, producing heavy precipitation.

“When I received the call to respond to the Emergency Operations Center at 3 a.m. on Sept. 12, my heart sank, but simultaneously my adrenaline kicked in.”– Deb Darnofall, risk manager, City of Longmont

“Many rivers, drainage ditches and irrigation channels filled with water to remove the large quantity of runoff. This increase in river discharge was so intense in some areas that it damaged the river gauging stations used to monitor the amount of water flowing in the river. Some river gauging stations that withstood the flows recorded the largest discharge since measurements began, while others recorded the largest flood in over 30 years.”

Last Major Flood Was 1941

Longmont had experienced flooding in the past, based upon how one defines flood.

“Since 1919, the St. Vrain River — which runs through the City of Longmont — has reached flood stage twice … 9,400 cubic feet per second [cfs] in 1919 and 10,500 cfs in 1941,” said Darnofall.

“These were both the result of severe rain events or ‘cloud bursts’ in addition to snow runoff. Along with these major events, 12 other years produced flow rates in excess of 2,000 cfs.”

Although the 2013 floods battered Longmont badly, procedures for such an event were in place, said Darnofall.

An aerial photo taken Sept. 14, 2013 of a flood-affected area of northern Colorado along the Big Thompson River, which was declared a federal disaster area.

An aerial photo taken Sept. 14, 2013 of a flood-affected area of northern Colorado along the Big Thompson River, which was declared a federal disaster area.

“Knowing that road closures were likely, I relied upon the state’s iPhone application for road conditions and closures. The response was amazing — the dedication and professionalism of the city workers was magnificent; the coordination of care of neighbors; [and] the faith-based, nonprofit and other governmental entities were magnificent. And the citizens of Longmont and the surrounding areas were … patient and resilient. It was my pleasure to serve, having had only a small part in the immediate response and recovery efforts.”

For Colorado as a whole, the damage caused by the floods was significant — and very widespread.

“You can’t control water — it will go where it wants to go and not always following the flood maps and zone designations.” — Duncan Ellis, U.S. Property Practice Leader, Marsh

According to the Colorado Department of Transportation, at one point more than 30 state highways or interstates were closed due to infrastructure damage or water standing on the highways. A total of 102 bridges were damaged or destroyed, along with thousands of houses and other buildings, and 10 people died. The economic cost of the flooding has been estimated at around $2 billion. Sadly for residents, little of the flood risk was insured.

Duncan Ellis, U.S. property practice leader, Marsh

Duncan Ellis, U.S. property practice leader, Marsh

“This was a very localized incident,” said Duncan Ellis, U.S. property practice leader at Marsh. “It didn’t really impact any major cities, but it was so violent that it almost erased some towns in the area. … It could happen again, this time over an area more populated, with more insurance coverage, and thus be even worse.

“The probability of getting such rain in one spot again followed by another bout of it is highly unlikely, but not improbable,” he said.

Exacerbating the problem, Ellis said, was that Colorado was suffering from drought conditions at the time. Drought causes the ground to become less absorbent, dramatically increasing the amount of runoff as well as causing significant erosion.

Locating Flood Areas

“The flooding in Colorado could encourage insurers to pay attention to the catastrophe sublimits in a policy, as well as locations — what’s near water or rivers,” said Ellis. “They could be looking at modern technology to map locations’ proximity to water.

“You can’t control water — it will go where it wants to go and not always following the flood maps and zone designations.”

A year after the floods and there is one question that needs to be asked: Could it happen again?

Darnofall has a very clear answer: “Absolutely. The mountain passes and year-round running rivers and streams have been created through erosion caused by melting snow, hail and rain over thousands of years.

“Mathematically, there is a 1 in 100 chance of having a flood event of approximately 10,000 cfs in any year. There is a 1 in 500 chance of having a flood event of approximately 20,000 cfs in any year.”

Darnofall said that the long-term attitude towards flooding in the area has changed.

“The reality shifted from ‘It could happen,’ to ‘It did happen,’ and we intend to be prepared,” she said. “We recognize the need to maintain and adhere to land-use regulations, strictly enforce flood plain management, recruit and train staff for experience in emergency operations, develop and rehearse emergency plans, and maintain healthy fund balances and reserves.

R9-1-14p40-41_05Colorado.indd“Real-world data from the September floods has been compared to the 100-year channel study. Primary changes have been made based upon an overlay comparison of actual flood outcomes compared to engineered estimates of what the waterways coming through the city would have done under similar circumstances.

Having to repair and replace the infrastructure damaged in September has accelerated the completion of the 100-year channel improvement timeline that was already in place.”

In the meantime, it would be fair to say that the insurance industry has been looking at the lessons that can be drawn from the Colorado floods.

Clare Salustro, manager of the model product management team at Risk Management Solutions, said that flooding has long been an area of concern for U.S. insurers, especially in the wake of flooding events from hurricanes such as Ike, Katrina, Irene and Sandy.

“Severe flood events happen every year, and can happen in any state in the country,” Salustro said. “These events have highlighted some gaps that modeling can help to fill.” She said that the main tools for understanding flood risk today are the FEMA Flood Insurance Rate Maps (FIRMs).

These maps provide limited information (i.e., 100-year flood extent and severity, 500-year flood extent) on flood risk for most communities in the United States.

However, as was seen during Sandy, some maps are severely out of date — FEMA last updated their maps in the 1990s for some of the areas affected by the 2013 flooding — and flood risk is mapped in piecemeal, with no unified set of input data or risk assessment technology.

“The insurance community has long been interested in having another view, apart from FEMA, which is where the catastrophe modeling community can contribute, said Salustro.

“Catastrophe models can provide consistent flood risk information, using the latest input data and modeling technologies, in a far more flexible format than FEMA FIRMs. For example, instead of estimating that the Colorado 2013 event was a 1,000-year event, this can be quantified, for different areas, using catastrophe model results. Even more severe events can be analyzed as well.”

Salustro added that the Colorado floods reinforced the issue of low insurance penetration in many parts of the country.

“Most residential flood insurance in the U.S. is provided through the National Flood Insurance Program [NFIP],” she said. “Participation in the program varies significantly — take-up of NFIP policies is highest along the Gulf and Atlantic coasts, where hurricane awareness is higher. Areas in the Midwest along major rivers such as the Mississippi River are also relatively flood-aware. But participation in the NFIP in the West is much lower, even though these areas are at risk to flash flooding, as seen in 2013.”

In the meantime, Colorado will mark the anniversary of the flood with, no doubt, mixed feelings. For those who bore the brunt, such as the people of Longmont, the fact that the dangers are now more apparent is cold comfort for those who lost property — or even friends or family. But the sad fact is that by studying what happened before, we can plan ahead for future events.

Marc Jones is a freelance writer based in London. He can be reached at [email protected].

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