Arkansas River development could worsen flooding

[RecycleMichael]

http://www.tulsaworld.com/news/local/planned-development-along-arkansas-river-would-worsen-inevitable-flooding-says/article_ac8a853a-d062-5bbd-84ca-19b67d690d74.html#.Unb1bV-wyL0.email

Planned development along Arkansas River would worsen inevitable flooding, says ex-official

Charles Hardt is worried. The city's former Public Works director is afraid those responsible for planning development along — and inside — the Arkansas River haven't taken into account the inevitability of a major storm upstream from the Keystone Dam and the flooding it would produce. "It's not a matter of if, it's when," Hardt said. The city in the 1970s and 1980s created a world-class flood-mitigation system that has been extremely effective along creeks and Arkansas River tributaries. But applying that same standard to the Arkansas River itself won't do, Hardt said.

"They were basically analyzing for the 100-year (flood) event," he said. "I am saying the 100-year event is not the measure you need to focus on the river." The 100-year-event standard means there is a 1 percent chance of flooding in any given year, or a 67 percent chance of flooding every 100 years. It is used to formulate building standards along the river, and that is where things get more complicated — and potentially more dangerous, Hardt said.

"We are talking about adding more things to the river banks — and potentially in the river — that could make the flooding worse and create the potential for a lot more loss of life and more property damages," he said. Hardt said development in and along the river can act as a "plug" that impedes the natural flow of the river — a flow that in times of heavy rainfall scours the river's bottom and banks to increase the river's capacity.
"You're encouraging development that is not compatible with the river's function, and that is to carry the water from upstream to downstream," he said.


Two major projects are to begin construction soon along the Arkansas River — A Gathering Place for Tulsa park and the River Spirit Casino expansion. Both are betting on the construction of low-water dams in the river to provide a steady stream of water. City leaders, meanwhile, have recently expressed a renewed commitment to constructing a dam in the river after getting a firsthand look at riverfront development in Pittsburgh, Pa., during a Tulsa Regional Chamber tour of the city.


Hardt's advice to them: "Visit with the people who most understand river dynamics, river hydrology and river behavior. And I would argue, to my knowledge, that is the U.S. Army Corps of Engineers." Kirby Crowe, with Program Management Group — which has done extensive work on the proposed Arkansas River dams — says that's already happened. The Arkansas River Master Plan, which envisions a series of dams in the river, has the Corps logo on it, Crowe said.

"They did this," he said of the plan. "Their primary mission is flood-risk reduction. They would not participate if it was adding additional risk." He noted that the dams are being designed to ensure that they do not cause a rise in water levels, either upstream or downstream. "The river doesn't know they're there," Crowe said.

Hardt's not just worried about the dams that might be built in the river. He's concerned about one that already exists — Keystone Dam, and he would like to see a major push to study and repair Corps infrastructure projects. "Its effectiveness and the maintenance of it and what its capabilities are needs to be well understood before we put other things downstream from it — other things meaning low-water dams, development along the river," Hardt said.

Harold Tohlen, the city's floodplain administrator, said the city's policy for developing along the river is fairly simple: Structures constructed along the river cannot increase the runoff on the property. When a new structure does create more runoff, detention ponds must be constructed to hold that runoff. At the same time, any structure built into the river must be done without creating a rise in water levels, either upstream or downstream.


Tohlen acknowledged that even controlled releases from Keystone Dam could create flooding downstream — as it did in Tulsa in 1986 — but said he feels comfortable with the city's 100-year standard. The city's approach is based on the "reasonableness of the frequency of (flooding) occurring," Tohlen said. "The city assumes for risk allowing development above the 100-year standard, that that is a reasonable risk to allow people."

Hardt, for his part, would like to see more open-space development — like the Gathering Place — because that type of development doesn't impede the flow of water. Hardt served as the city's Public Works director from 1990 to 2011. So he knows some people will question why he didn't address the flooding issue when he was on the job. And he can't blame them.

"I could be criticized — and I should be criticized — for not having done that," he said. "But we saw no political will at that point."

[Conan71]

"No political will"

What a predictable comment from a classic government bureaucrat.

Just glad he's finally moved on.

[SXSW]

I don't get those that argue the Arkansas is a prairie river and should be left alone.  It was a prairie river before it was dammed up and its banks stabilized.  Having water in the river creates an asset, which the Arkansas can be in Tulsa.

[cannon_fodder]

Development anywhere makes flooding worse.  Pavement increases runoff.  Structures prevent flow.  Bridges limit flow.  Concrete stream beds create faster, more dangerous currents.

With the Arkansas, unless Keystone fails the flooding is mitigated.  And if Keystone failed a few shops, restaurants, or docks on the river isn't going to be the concern.

[Vision 2025]

The thing I find concerning is that Charles advice is to "Visit with the people who most understand river dynamics, river hydrology and river behavior. And I would argue, to my knowledge that is the U.S. Army Corps of Engineers."  Well, THEY (The USACE) WROTE THE MASTER PLAN and Charles Hardt was there as the City's representatives throughout the process...  

The Arkansas River Corridor Master Plan includes recommendations for development standards that are above the 100 year event to the flood of record (1986) plus one foot that to date only Jenks has adopted.  This criteria was presented to Tulsa, I know because I attended the meeting of the City's Storm Water Advisory Committee when it was and it evidentially went nowhere.  As for the LWD's, the design criteria includes "zero rise" at the 100 year flow, and "zero rise" at the levee design flow which is significantly higher (also higher than the flood of record in 86) and Zink which is the prototype passed these as reviewed by the CORPS... FYI - the final draft of the Zink 404 permit has been issued.

Lastly, no one wants flooding but the River is changing and will never again be a Prairie River. 

Kirby Crowe

[AquaMan]

I totally understand Hardt's concerns. In this case, small details really matter a lot.

Go over to look at the construction on the 75 244 bridge and note what has happened. In order to remove the old bridge and construct the new one they had to build up the area under the bridge with dozers and crushed rock. A low tech, low water wing dam is what they have created. Immediately that created a nice little lake upstream towards the natural rock formation that creates a jetty across the river. This is where Confederate troops lost track of Union sympathizing Native Americans they were trying to round up.

The next thing you will notice is that within a month or less, low flows drained the little lake and what was left was sand bars that now nearly cover the jetty. When the little lake was created, it changed the flow dynamics of that area and the lake will gradually fill with sand if the river is not allowed to naturally scour it. This plains river is loaded with suspended sand from its tributaries and from the Keystone impoundment which is suffering the same fate as our little temporary lake.That means a shallow reservoir that will flood easily when high flows happen.

The key to me is the changing climatology that seems to indicate heavier storms and more intense runoff from developing areas that drain into the river and the fact that we have based our estimates on the last hundred years rather than the next. Maybe I just haven't seen those details and Kirby has. I don't remember seeing any features, on any of the commonly accepted designs, that will naturally scour the river. I don't see any plans for regular dredging either. So, unless other designs are seriously considered that keep the water moving you can expect that any lakes created are likely to fill with sand and increase the probability of flooding downstream.

BTW, its still a prairie river in nature. I can put a rev limiter on a chevy Corvette, but its still a Corvette!