By Lois Mittino Gray
Tom Straw pores over topographic maps and computer printouts doing pencil computations and line drawings to help explain why he believes the two highest recorded floods on the Wabash River are anomalies. He feels neither figure should be used by experts to determine the highest elevation necessary for designating a class A floodplain as they do not represent the ‘unaltered flow of the Wabash.’ The issue is a major one affecting the community of New Harmony at the present time as it threatens homeowner’s wallets and the overall economy when the new FEMA floodplain map goes into effect in November.
Straw is a hydrologist/geologist professor and consultant who has worked in this field of study for many decades. However, unlike many of the other professionals, he was alive to see and live through the historic 1937 and 1943 Wabash River floods as a child in Griffin. He was born in 1931 in a home about 100 yards from the river in a place called Shiloh and well remembers time spent on the river as his parents had a business mussel shelling and fishing.
“I remember water everywhere and someone saying that we had to go to the post office to get our tetanus shots. Ouch.” He explained that water-borne typhoid fever was a very real threat back then as there were mostly outhouses and they were flooding and spilling out into the floodwaters.
The highest flood level recorded at the New Harmony gaging station was in 1913 at 27.7 feet. “They should not use that number to predict how the Wabash will function normally as it was a non-hydrologic event. We need to convince the DNR and then the people at FEMA that this does not represent unaltered flow. It is a discrepant event in science terms and not relevant.”
Straw says that the flooding was caused by the breaking of a railroad embankment up near Mount Carmel, Illinois. “Books call it a tsunami, but they did not use that word back then. They would have called it a tidal wave,” he explained. When the water came pouring southward, it split in two directions around the elevated Mumford Hills of Griffin. The water to the east side had only four outlet bridges to get past the upraised railroad bed and it backed up and flooded. Water headed to lower elevations and rushed down to the open New Harmony area.
The 1937 flood level was the second highest recorded at the New Harmony gaging station at 24.40 feet. Straw feels that is also an anomaly because it was not Wabash water causing the flooding, but rather backflow from the Ohio River. This hit home when, as a young man, he heard Allen Cook tell a story at the Main Café of being in a boat during the 1937 flood and the current was pushing it northward up river. “The backflow water pushing up the Wabash from the flooded Ohio River was changing the river flow.”
“I also remember hearing heated conversations after the ‘37 flood around the counter at JP Geisler’s service station in Griffin. Through the haze of blue smoke, men would gather and argue if a flood on the Ohio River could really affect the Wabash. Well, they’re all dead now that I know the answer and I can’t tell them, but it is definitely, yes.”
“If that water was coming from the Wabash and not the Ohio, then upriver cities like Vincennes and Petersburg on the White River would have that flood in their top ten list and they don’t. It is a hydrologic concept called the backwater curve and it hit around New Harmony”
Straw wonders if these two unnatural floods were used in the computations for the floodplain map that sets the new elevation of 381.6 feet as the number for the out of floodplain area designation. Doing the math, he added the bottom elevation datum of 353.07 feet to the ‘37 flood number of 24.40 feet and the sum is 377.47 feet. If you add the 1913 figure of 27.7 feet, the sum is 380.77 feet. Even with these two flood event sums, the elevation is still below the new number set at 381.6 feet. The third highest flood is 1943 at 23.67 feet and that total elevation sum is 376.7 feet. Most of New Harmony is at 380 feet above sea level and that is well above these sums. The new higher number will place homeowners in a Class A floodplain using the new figure of 381.6 feet affecting new construction and flood insurance costs.
In addition, Straw says that dams were put in along the Wabash in the early 60’s to control flooding creating Lake Monroe, Mississinewa and Salamonie Reservoirs and Cagle’s Lake. “We need to know what information the DNR and FEMA included in their 25, 50 and 100 year flood map projections. They do volume of flow graphs with numbers using dams and non-dam figures.”
DNR Representative Gary Bowman spoke at a public meeting in May and said that the maps are based on two things. One is the elevation of the land which Straw explains gently undulates from about 374 feet to 380 feet around here. Did they use contour lines or digital elevations he questions? The other is a curved line that connects the crest of a top 1% flood as it move downriver like a wave. They need to update the curve map and remove the top two flood numbers he feels.
In a few years, the DNR talks like it will have a brand new more correct map using LIDAR technology. “They need to get on it and get it accurate, before they do things that affect the people so much. It bothers me the way the government does our business.”
By Lois Mittino Gray