They designed a pilot study using remote sensing technology to monitor changes in the open water area of the county, a rural area with less than half the population of the city of Devils Lake. The first conclusion, he said, was that between 1989 and 2001 — the study period — there was “an explosive and dramatic change in open water conditions throughout the county.” A drought-to-deluge cycle
In 1989, the county, like most of North Dakota, was in the midst of an extreme drought, which was followed by an extended wet period. That study period captured nearly the entire range of naturally occurring hydrologic variation, observed Todhunter and Rundquist. For scientists, such a range of observable natural phenomena delivers an optimal opportunity for analysis. “It was a drought-to-deluge spectrum,” Todhunter said. The wetlands in that area expanded largely as a result of overflow from Stump Lake. “Stump is also a terminal lake, which means it takes in water from the surrounding area. As it grew, so did the wetlands in the surrounding upper (Devils Lake) sub-basin,” Todhunter noted. “We looked at the change in open water area. “So we analyzed remotely sensed imagery and other digital datasets to document the expansion of Stump Lake and the growth of the wetlands and other open water areas in Nelson County,” he continued. “We found that the extent of wetland expansion was much more significant than originally realized.” In the 10-year wet period from 1992 to 2001, Stump Lake expanded in area by 53 percent, while the open areas associated with wetland ponds gained 426 percent. Rundquist’ s analysis of the images and data produced conclusive evidence: “In Nelson County, 92 percent of open water area expansion was due to wetlands, not flooding from the lake.” What to do?
“We clearly identified that wetlands can create a flood hazard as well as a lake or a river can,” Todhunter said. “This is flooding due to wetland expansions.” Todhunter concluded that there’s not much to be done about this flooding other than to plan for it. “Our hydrologic analysis of precipitation records shows that changes in rainfall produced this widespread expansion of wetlands in our study area,” he said. The popular press tracks the “nature-nurture” flood debate: the basic controversy between folks who see rainfall as the problem and those who see drainage as the problem. “Some people state that flooding results from changes in basin hydrology, such as drainage,” Todhunter noted. “But hydrologists say most of the flooding is actually the result of rainfall regime changes.” Precipitation records since 1940, he notes, point to a fundamental shift in precipitation in northeast North Dakota, including the Devils Lake basin. Wetland misconceptions
“We’ve seen a long-term shift from very dry to much wetter conditions, and this is the primary driving force in the rise of Devils Lake and the significant expansion of wetlands in the region,” Todhunter said. Can or should anything “be done”? “I think not,” Todhunter said. “Wetlands are natural parts of the environment, and they serve numerous positive functions, including biodiversity and wildlife habitat.” However, he continued, the other side of the argument is that there are some misconceptions about wetlands. “I think that we’ve begun to overvalue wetlands in terms of their hydrologic significance,” he said. “Yes, they can reduce flood peaks by storing water, but the impact of that benefit for really big floods is largely overstated. The positive impacts of wetlands are minimal in really large floods such as this year.” Todhunter noted that historically “we’ve gone the whole route from the late 1800s when wetlands were viewed as ‘wasted’ land and sources of disease, and we ‘reclaimed’ them well into the end of the last 20th century, when we turned them into something we saw as positive.” The major challenge now is to reckon with the economic impacts of widespread expansion of wetlands and associated flooding on rural communities that are not in a position to benefit from their recreational and tourism benefits. “This can have negative economic consequences that have to be appreciated,” Todhunter said. “This isn’t a call to start filling them in, but we must recognize that when we get these very wet cycles, low-lying areas that don’t normally store water start storing water, and that impacts agriculture and rural communities.” A dramatic impact
In Nelson County, for example, the effect of wetland expansion on farm production has been dramatic. Largely a farm county, a lot of land there normally is given over to crops. Over the last 10 years, however, almost half of that farmland has succumbed to the negative impacts of flooding or been either put into the federal Conservation Reserve Program (CRP, a crop land retirement program) or received flood-related crop insurance claims. “We’ve seen late and prevented planting, a very high rate of plant-diseased crops, and waterlogging,” Todhunter said. “For a county like Nelson, to have 50 percent of farmland out of production or flood damaged is a major economic impact. Whenever farmers don’t plant, or don’t harvest, it has significant impact upon the local service economy.” Ultimately, Todhunter said, his study of wetland-related flooding in Nelson County was about “putting hard numbers to the actual goings-on. Our intent was to put numbers to something we knew about, something that’s a natural part of the environmental ebb and flow.” Beyond the specifics of his study, Todhunter notes, there’s wider evidence that over the past 10,000 years there really hasn’t been a stable climate regime in this region. “The paleontological records show that there are constantly changing hydrologic conditions in this region,” he explained. “These drought-to-deluge shifts and their reversals are not out of the ordinary. They’re actually very typical for this region.” |
Dimensions
Devils Lake, a community of about 7,200 people, gets a great deal of news coverage about rising lake levels and the flooding that’s soaked up a lot of real estate.