The deluge of ’93: litmus test for floodplain forests – the Great Midwestern Flood of 1993 – includes related articles

The deluge of ’93: litmus test for floodplain forests – the Great Midwestern Flood of 1993 – includes related articles – Cover Story

Michael Hanback

A look at the known, suspected, and political aftershocks of last summer’s millennial maelstrom in the Midwest.

Go ahead and pencil it into the history books. The Great Midwestern Flood of 1993 will be remembered as one of America’s most devastating natural disasters.

Fueled by months of steady rains and intense spring storms, Mississippi and Missouri rivers went mad last summer. The raging rivers and their turbulent tributaries welled from their banks to overtop and breach more than 1,000 levees in nine midwestern states.

Cresting 10 to 30 feet above flood stage in places, the record-high flows scoured the countryside from Minnesota to Missouri. A witches’ brew of muddy water roiled through cities and towns, causing widespread heartbreak and destruction. Millions of acres of once-fertile croplands and biologically diverse marshes and forests were inundated for months.

A year after the deluge, which claimed nearly 50 lives and inflicted in excess of $12 billion in property and agricultural damage, Heartlanders continue to put back together their shattered homes, lives, and dreams. And federal and state officials are focusing on the ecological aftershocks of what many consider to be a once-in-500-years occurrence.

How did the flood affect trees, forests, and forestry operations in the upper Mississippi and lower Missouri river basins? How will the record-setting deluge impact natural-resource management throughout America’s largest inland floodplain ecosystem for years to come? Much of the information flowing out of the Midwest is speculative, but some trends are emerging.

“Flooding is a normal part of the riverine process, a mechanism that’s important to floodplain ecology,” says Barry Drazkowski of the Environmental Management Technical Center, a Wisconsin-based U.S. Fish & Wildlife Service research facility that focuses solely on the Mississippi River. “But it does result in some ecological changes.”

Last summer’s massive flood imparted profound and often permanent change to thousands of acres of woodlands across the Midwest. Swollen rivers and streams scoured bottomlands and ripped new channels through the adjoining countryside, eroding soil and uprooting trees and other vegetation.

Near the confluence of the Mississippi and Missouri rivers just outside St. Louis, forest damage was extensive. In Iowa, many woodlands rimming the Mississippi River were also hard hit.

“Some areas where the currents came in look like moonscapes,” says Frank Hershey, a watershed specialist and forester for the U.S. Forest Service.

The majority of the flood’s direct damage to trees occurred on private lands that sat hard against raging waterways. But many acres of state-owned woodlands also bore the brunt of the flood’s fury.

A spokesman for the Kansas Department of Wildlife and Parks said, “The floods destroyed the habitat on major public areas like Tuttle Creek and Milford reservoirs.” Missouri estimates $300,000 damage to facilities and resources on Eagle Bluffs Conservation area alone. Iowa reports that Ledges State Park, located along the Des Moines River, suffered devastating soil erosion that resulted in a loss of timber. Similar reports stream out of most Midwestern conservation departments.

Though the floodwaters directly impacted soils, trees, and forests in many areas, the most dramatic destruction was largely localized. “The only places where trees were rooted out were in certain areas along riverbanks with high-energy flows,” says Hershey.

After eight months of abnormally heavy rainfall and the subsequent summer deluge, the major cause of widespread trouble for trees was the long-term inundation of bottomland forests during the growing season. Rivers and streams steadily rose, raced from their beds, and spread out over millions of acres of countryside. In many areas, the floodwaters filled historic (but now leveed off) floodplains 10 to 30 miles wide. The excess water lingered for months.

“We’ve never had a reporting of such an extended inundation of trees and roots,” says Jill Pokorny, a Minnesota-based plant pathologist for the U.S. Forest Service. “And the fact that the flood occurred during the growing season was a big factor. Trees and roots can sustain inundation and lack of oxygen much better during their dormant period.”

According to Bruce Palmer, forestry information specialist for the Missouri Department of Conservation, “A lot of our trees were underwater the first of July, and we had more flooding late in the summer. Some trees were underwater for almost three months.”

Late last fall, U.S. Forest Service officials in Minnesota released an informative resource packet titled, Flooding and Its Effect on Trees. The report stated: “The longer trees are exposed to flooding, the greater the potential for injury. Most trees can withstand only one to four months with water continuously over the soil surface. If flooding is recurrent, injuries (to trees) will accumulate and serious damage may occur.”

Is this prediction, along with other long-held theories regarding trees and their tolerance to floods, proving true across the Midwest? The ’93 deluge is serving as the ultimate litmus test.

“We’re learning a lot about trees and their adaptability and tolerance to floods,” says Hershey, who is currently evaluating flood-stressed trees in Missouri and Illinois.

Cottonwood, green ash, sycamore, silver maple, pecan: According to Hershey, these species, which have adapted to the floodplain over time, are faring pretty well.

“Take pecan, for example. Some of those trees down in the Mississippi River floodplain were inundated at least six weeks, maybe eight, while in full leaf during the growing season. Today they look fine.”

Hershey is finding that other species, such as pin oak and river birch, have a limited ability to tolerate floods. And he says that many ornamental trees planted in urban and suburban areas suffered mightily during the deluge.

“Take your red and white oaks and hard maples,” Hershey says. “They provide a good fall color show, so they’re planted around residences and in recreation areas.

“They were growing well in places, but they’re made for the uplands and weren’t adapted to flooding. When the floodwaters got onto them, they succumbed pretty quickly, probably within a week. You could see that by the end of last August.”

For trees adapted to the floodplain, water depth played a significant role in their fight for survival. Generally, foresters are finding that in high-water areas, mature, vigorous trees fared better than smaller trees and seedlings.

“In many places, trees four to six inches in diameter were bent over, covered with water and mud, and killed,” says Hershey.

The big losers were seedlings of all species. Says Pokorny, “You just knew that seedlings completely covered with water were not going to survive. Their leaves weren’t photosynthesizing; their mechanics were shut down.”

Throughout the Midwest, few state seedling plantations are located along flood-prone rivers and streams. Still, the abnormal rains of 1993 took their toll on state and private nurseries planted outside the floodplain.

“Heavy rains and extended flooding in seed beds are going to be very damaging potentially,” says Pokorny. “One of the big things we’ll see is Pythium root disease.”

Officials are monitoring the potential onslaught of diseases and insects that may kill not only seedlings but all sizes of flood-stressed trees. Trees may battle for years to ward off attacks from diseases and insects.

“There was a lot of debris floating down the waters, inflicting damage to trunks of trees,” says Pokorny. “Those types of wounds open the door for a myriad of things. I expect that surviving trees with large wounds are going to develop canker diseases. Also, wood-decay organisms enter through wounds. We’re going to get a succession of opportunistic fungi and insects that move in secondarily on trees.”

Yet another flood-related factor will impact surviving trees and reforestation across the Midwest. As rivers and streams breached levees and roared across croplands, they swept away tons of topsoil and deposited record amounts of silt and sand in fields and forests. Today sand depth measures several inches to 10 feet in places. Ironically, most of the sand came from rural levees that were scoured, blown out, or overtopped by floodwaters.

Missouri, Iowa, and Illinois have initiated a cooperative-research program to evaluate, among other things, the effects of siltation on existing trees and the regeneration of forest understory.

“There’s lots of sand in the bottoms,” says Missouri forester Palmer. “What kind of regeneration we’ll see will be interesting.”

According to Hershey, many species of floodplain trees are adapted to the sand. “Cottonwoods in particular can go in and invade the sand by seed,” he says. “But at a given point there is too much sand for some species. Pin oaks, for example, are more adapted to silt and clay. “I think we’ll see that we can plant trees in the sand, but it’ll take some time to build up organic matter.”

While studies are ongoing, some experts see a silver lining in the flood’s massive moving of topsoil and sand. Tons of sediments deposited throughout midwestern ecosystems were nutrient-rich and critical to backwater plant production. In many areas, the flood’s extensive natural fertilization of aquatic and herbaceous plants will help rejuvenate the land and provide lush feed for fish and wildlife for years to come.

“It was like pushing an enormous reset button for plant succession all along the Missouri River,” says Terry Robison, a reforestation specialist for the Missouri Department of Conservation.

In the flood’s wake, federal and state forestry professionals, as their tight budgets permit, are initiating forest-recovery studies across the Midwest. But few tree plantings and salvage operations are ongoing. Seems the great flood is still wreaking havoc.

“In February we tried to get out and check some forested areas,” says Hershey. “But many roads and bridges are gone, and the soil was still wet and mucky. Unless you had a helicopter, it was hard to get to many places. Anyone who plans to harvest timber has those same restraints.”

As experts evaluate the aftereffects of the deluge, they are laying groundwork for long-term forest-management plans. At this phase of the game, the most important plan calls for the extensive planting of trees along agricultural levees.

Officials are finding that corridors of trees protect levees by blunting the force of floodwaters and screening out damaging debris. Border trees help lessen soil erosion and sand deposition.

According to Steve Young, wildlife biologist for the Missouri Department of Conservation, “Aerial photos make it clear that trees protected levees. Forested buffer zones as narrow as 100 yards saved many levees from damage and reduced the severity of damage to others.”

Young points out that many flood-ravaged fields will never be returned to agricultural production. The cost of scraping up and hauling off huge deposits of sand would be prohibitive–as much as $20,000 per acre in some areas.

“When you consider how many years of crop production it would take to pay for rehabilitating such areas, you realize it just isn’t going to happen,” he says.

Young and other natural-resource professionals say that sand-covered fields and adjacent wetlands scoured by last summer’s flooding could be converted to forest-buffer zones at extremely reasonable rates. Part of the cost of planting cottonwoods, willows, or other trees adapted to riverine settings could be subsidized through one of several government programs, such as the Forestry Incentive Program administered by the Agricultural Stabilization and Conservation Service.

“We’ve always known that natural solutions to flooding problems were better for wildlife,” adds Missouri biologist Larry Heggemann. “What’s hard for people to realize is that a streamside corridor of trees can also be the most economical way to protect your land.”

In the flood’s aftermath, the future of innovative forestry operations is just one seam in an enormous political football being tossed around by politicians, natural-resource professionals, landowners, and environmentalists across the Midwest and in Washington, DC.

Congress will soon hold hearings on the effects of federal levees on the flood of ’93. According to many scientists, as levees continue to be constructed along the Mississippi and Missouri rivers, water depths and pressures increase, actually flood problems in some areas.

Conservation and environmental groups are urging politicians to rethink levee building. They say that if levees were moved back and river channels allowed to widen, the riverine ecosystems would respond with additional wildlife habitat and flood-storage capacity.

The Clinton Administration is in the ball game. Last August it announced a new wetlands policy, which aims to protect America’s 270 million acres of remaining wetlands and create new habitats as both a conservation and a flood-control measure.

According to Agriculture Secretary Mike Espy, one way to do that is to purchase entire midwestern towns devastated by the floods and convert the areas to absorbent wetlands.

Also, there is legislation on Congress’ plate to revamp the federal flood-insurance program. The program’s bargain premiums, critics say, encourage development in flood-prone areas but cannot begin to cover big-money flood damage.

How much flood-damaged land should be reclaimed in the Midwest? How many acres should be converted to wetlands? To what extent should the federal government subsidize landowners and farmers whose properties were damaged by the flood? Should damaged levees be rebuilt, moved back from the rivers or leveled altogether? The floodwaters may recede and the forests may dry, but the political impacts of the 1993 deluge will be felt for years to come.

In the end, what is the current health of our mid-western woodlands? Two forest components–the water and the wildlife–appear to have successfully weathered the deluge.

Most experts believe that last year’s extraordinary rains flushed out the gut of the Mississippi and Missouri rivers, providing a boon to America’s largest floodplain ecosystem. The floodwaters drove silt and contaminants from the beds of rivers, streams, and pools, cleansing and expanding waterways.

Owing to enhanced habitat, many populations of fish, such as bass, bluegills, and catfish, are exploding. Some species of wildlife, especially ground-nesting birds like pheasants and wild turkeys, suffered short-term hits from the floods. But persistent rains filled potholes and marshes across the upper Midwest. After 10 years of drought, waterfowl production thrived.

Floodwaters displaced many white-tail deer, gray squirrels, and other wildlife, but only temporarily. The animals filtered back into their traditional riverbottom habitats as crests receded.

The condition of soils across the region is perhaps the biggest question mark. Extensive erosion occurred in many areas, and enormous sand and silt depositions remain. Soils are still saturated in many areas. It will take months for officials to get a firm grip on the flood’s effects on soils.

And what about the forests and the trees?

“Some trees, such as upland oaks and hard maples, were prone to die,” says Hershey, who has spent many hours afield evaluating flooded forests in the Mississippi River floodplain. “As for the adapted trees, we don’t really know yet. I wouldn’t expect to see a lot of outright mortality, but I don’t think we’ll know much for sure until spring leaf-out.”

For sure, given a normal spring and summer, nature’s amazing process of reforestation will begin to occur in the upper Mississippi and lower Missouri river basins. Which species of trees and plants will dominate the flood-changed woodlands?

“Whichever seeds fly first onto bare ground, we’ll see clumps of that type of vegetation,” sums up Hershey. “That’s the pattern of riverbottom vegetation.”

PLANTING A FLOODED ISLAND

While last summer’s Flood of the Century was receiving international attention, a small matter was playing out that could have had an impact on our Global ReLeaf Forests program of restoring native trees on damaged ecosystems. As the floodwaters receded, AMERICAN FORESTS staffers wondered whether the Mississippi River island we were planning to plant was still there. As it turned out, the island did survive, and reforestation plans are moving ahead. So now we can tell the “rest of the story.”

About two years ago, Shannon Ramsay of Iowa’s Trees Forever alerted AMERICAN FORESTS about a cost-sharing opportunity to establish another Global ReLeaf Forest (the program was formerly known as Heritage Forests). This restoration project was unusual because it involved 500-acre Long Island in the Mississippi, in Adams County, Illinois.

Managed by the U.S. Army Corps of Engineers, the island is also within the boundaries of the Mark Twain National Wildlife Refuge. Funding for wildlife-improvement projects on such lands is authorized by federal law–provided that 25 percent of the money comes from non-federal sources. That’s where Global ReLeaf Forests and Trees Forever became part of the equation.

Prior to its acquisition by the federal government, Long Island was subjected to agricultural clearing and to periodic flooding. Federal protection allowed the land to revert back to trees, but “invasive” species of elm and silver maple took over, rather than the historic mast-producing species that provide valuable food for wildlife.

The five-year project calls for restoring mast-producing hardwoods on some 480 acres of abandoned agricultural leases and old fields. There have been several delays (the flood itself being one) in the approval process, but now the project is back on track, and we’re hoping the plantings will begin late this year or next spring.

The Global ReLeaf Forests program gives private-sector donors the opportunity to help heal damaged forest ecosystems on public lands. If you wish to contribute or need further information, please contact AMERICAN FORESTS, Attn: Bill Tikkala, P.O. Box 2000, Washington, DC 20013 (800/368-5748).

AN IOWA PERSPECTIVE

On a sunny day last March, maple-syrup maker Joe Parrott delivered 250 gallons of sap to the sugar house at Cedar Rapids, Iowa’s Indian Creek Nature Center, which I oversee. While unloading, he clicked on the radio. A flood alert had just been issued, and the radio warned residents of low-lying areas to brace for rapidly rising river levels the next couple of days.

Joe was concerned. Most of his 150 sap buckets hung from large maples hugging the banks of Indian Creek, a tributary of the Cedar River.

Ironically, the same conditions triggering the predicted flood were producing record sap flows. We’d enjoyed several days of warm, sunny weather that was rapidly melting a heavy pack of snow and ice and stimulating maples to gush sap.

Joe was reluctant to pull in the buckets during one of the best sap flows in years, and we agreed to wait until the next day to see if the river would really rise. That was a mistake.

Overnight, a huge mass of cold water overwhelmed the creek and river. By morning floodwater was rising toward the buckets. Joe retrieved as many as he could . . . by boat. Others were swept away by the swift current, and a few reappeared, full of thick mud, when the flood finally ended five months later.

The Midwest’s 1993 weather was amazing. Once the snow melted, a pattern of drenching rains settled in. East-central Iowa received over 60 inches of precipitation during the year, almost double normal. Much of that fell during the summer on saturated soil and already swollen rivers.

The flood season climaxed on the evening of July 4. Bulbous-looking clouds appeared to hang suspended over the land while dumping incredible amounts of water. Seven inches fell overnight, the heaviest rainfall ever recorded in Cedar Rapids. On the morning of July 5, a wall of water roared down area creeks, sweeping away bridges, trees, houses, barns, and millions of tons of soil. A day later the flash flood was over, but rivers again rose to record levels, flooding valleys with silt-laden water.

By early August most of the water had nearly drained away; then another seven-inch downpour repeated the process. It wasn’t until after Labor Day that the weather pattern finally switched back toward normal and the land began drying out.

The 1993 floods impacted crops, businesses, livestock, wildlife, and trees. Some of the effects on trees were glaringly obvious. Others will take years to gauge.

Most obvious were thousands of trees felled by raging waters. Huge old cottonwoods and silver maples, the soil washed from their roots, tumbled into the flood and floated around whole, gouging chunks of bark and sap-wood from survivors, Other trees were killed, stressed, or stimulated by inundation and sedimentation.

The intense weather brought water to trees not usually considered flood-tolerant. Large bur and white oaks on dry upland soil, for example, were flooded for the first time in their long lives. No one is certain of the long-term impact of flooding on these species. Death could be delayed for several years.

Box elders, silver maples, sycamores, and green ashes seemed to love the extra water. Some silver maples that Joe Parrott had tapped in February grew so much, despite inundation, that the tapholes were completely healed over by midsummer.

According to the Iowa Department of Natural Resources, fewer trees will die in areas where the soil was merely saturated than in areas covered with water. Once an area is inundated, water depth doesn’t matter until a tree’s foliage becomes submerged. Even flood-adapted trees that had their crowns totally covered will likely die. Whether a tree survives depends on its species, the percent of its crown that was submerged, and the duration of flooding.

1993’s fluky weather impacted even plenty of trees that were out of reach of the flooding.

“During most of the summer we had an abnormally low amount of storm damage to city trees, simply because all of the rainstorms came without much wind,” said Cedar Rapids Urban Forester Eric Faaborg.

That changed on the night of August 14, when a raging storm brought both heavy rain and driving wind. “We lost hundreds of large, healthy trees that night,” Faaborg said. “Many simply tipped out of the saturated soil.” Massive veterans were uprooted along city streets, in parks and yards, and in the woods.

There was one silver lining to the dark clouds that dropped so much rain: Only a small percentage of the region’s trees were flooded or blew over. Many of the survivors grew at record rates. And all the moisture helped newly planted trees survive.

“We had some trouble keeping weeds away from new street trees, but all in all they did very well last year,” said Faaborg.

NUGGETS FROM OUR 100 YEARS

American Forestry October 1915

Cutting Walnut Trees

A newspaper dispatch from Leavenworth, Kans. says: “There will be no walnut trees left in this part of Kansas and across the river, in Missouri, if the European war keeps up much longer. At present three bands of men are cutting walnut trees down and sawing the lumber into 12-foot lengths, shipping them to the East by fast freight.

The walnut lumber is wanted for gun-stocks for rifles for the European armies. All trees more than 6 inches in diameter are purchased, and a good price is paid for the lumber. Those selling the trees have not been informed what country the wood is destined for.

Michael Hanback of Warrenton, Virginia, a field editor for Outdoor Life magazine, has written extensively about the Midwest flood.

COPYRIGHT 1994 American Forests

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