The Explicated Floodwall
Reprinted, with permission from the premiere issue of Midtown Magazine courtesy of the author, Bill Beranek, and Midtown’s editor and publisher, the esteemed Tom Healy of Apple Press.
White River Flood Risk Management — Final Stage
Where and how should the flood project along the left bank of the White River at Broad Ripple and downstream be completed? The answer will affect future vitality of Midtown neighborhoods.
How you feel about the project depends in part on where your property is situated. You may want to be freed from the federally mandated flood insurance and building code restrictions of the 100-year flood plain as soon as possible, or you may want reduced risk for flooding events. But all Midtown residents want to avoid any negative impacts that a permanent, intrusive structure could have on neighborhood vitality.
A flood wall now extends from the north side of Broad Ripple Village south to Kessler Boulevard. A new section is under construction along the river to the northern edge of the Riviera Club (see red line on map). If the barrier is not continued to high ground, flood waters could overtop the river banks near 56th Street and flow back into some low areas behind the wall.
The US Army Corps of Engineers (the Corps) describes its position in a June 7, 2013, Final Supplementary Environmental Impact Statement. The public comment period ends September 6, 2013. The City of Indianapolis must then make a choice before the Corps completes its Record of Decision.
While the Federal Emergency Management Agency (FEMA) is focused on 100-year flood protection, the Corps has determined that 300-year flood protection is feasible for this project and has identified two alternatives to accomplish the goal:
1. Westfield Boulevard Flood Wall Alternative ($15.6 million)
A flood wall would continue south along the river bank on the west edge of the Riviera Club, cross the Central Canal public water supply with a flood gate, and continue south from Capitol Avenue with a 3,100-foot wall between Westfield Boulevard and the canal, until ending in the hill behind Holcomb Gardens at Butler University (see yellow line on map).
2. Illinois Street Flood Wall Alternative ($13.8 million)
A flood wall would extend along the northern boundary of the Riviera Club, then south along the west side of Illinois Street, cross Illinois Street with a mechanical gate, extend south between Westfield Boulevard and the canal, cross Westfield Boulevard with a mechanical gate at the north edge of Chase Bank, and extend to the hill behind the bank parking lot (see turquoise line on map).
The Westfield Flood Wall Alternative protects the entire Warfleigh Flood Plain from Broad Ripple to Butler-Tarkington. This is the Corps’ first choice but due to public opposition, the City of Indianapolis last November told the Corps that it would not participate in that option. City participation is required for the Corps to proceed.
The City prefers the Illinois Street Alternative. Although this option provides no flood risk reduction for businesses and residences south of the Riviera Club that the Westfield Alternative would protect, the City administration considers this to be the quickest path to increased property values and tax revenues from development of structures on the properties in a substantial part of the Warfleigh and Broad Ripple neighborhoods.
The Corps has described three variations on these options that it could participate in if the City paid all of the excess costs. The preferred option has been the 56th Street Flood Wall, which places a wall along the Riviera Club river bank, turns north along the tow path, crosses the canal with a flood gate at 56th Street and bisects the 56th and Illinois streets commercial district with walls and gates (see pink line on map).
Two others options are variations of the Westfield Boulevard Flood Wall. One places a canal flood gate at Graceland Avenue instead of Capitol Avenue, using a flood wall to protect the canal along that section (see orange line on map). The other is the original Westfield Boulevard alignment but using removable panels for the top sections of the wall. The base would be built to the height necessary to remove Warfleigh from the 100-year floodplain, and the top panels could be added to capture a 300-year flood, which the Corps needs for its engagement.
Concerns About the Proposals
Opponents have raised the following objections to these alternatives.
A. Flood Gate Across the Canal
All alternatives include a large flood gate across the canal, which is a focus of opposition for three reasons.
1) Recreational Use: Supporters of the canal as a key social and cultural amenity for nearby neighborhoods claim that the canal flood gate will physically split the canal greenway into two distinct pieces: one section north to Broad Ripple and another section south to the Indianapolis Museum of Art. The canal’s function as a unifying agent in Midtown will be lost.
2) Canal Operations: A canal flood gate increases the difficulty of managing weeds, sediment, and water flow in the canal.
3) Reliability: Maintenance of the flood gate would be the responsibility of the Indianapolis Department of Public Works or an outsourced contractor, rather than the canal owner. Any malfunctions during the coming decades of operation could shut down Indianapolis’ largest water source. Passive flood risk management (such as a wall or levee) is more dependable than flood control that requires ongoing funds for special maintenance, trained staff available to take action, and a steady source of electricity.
B. Vulnerability of Flood Damage to the Canal
Neither of the Corps’ two alternative recommendations protects the physical integrity of the canal at the 56th Street river bend. The rushing current of the flooded river could weaken the canal berm by overtopping with a level as low as a 50-year flood. A prolonged overtop condition could cause erosion of the inside of the berm and collapse of a section of the canal. Depending on the damage, flow of water to the main downtown treatment plant could be halted, followed by a period of reduced flow to the system while the damaged portion of the canal is rebuilt.
C. Westfield Boulevard Flood Wall
Opponents of the Westfield Flood Wall say the height and length of that wall would physically and visually isolate the Town of Rocky Ripple and the canal itself from the Butler-Tarkington neighborhood. They worry that the long wall could attract graffiti and create an unsafe environment for walkers and joggers. In this alternative, the road crossings at 52nd and 53rd streets will not use mechanical gates but instead rely on construction of a three-foot-high sand bag wall, blocking the roads well in advance of any predicted flood event. Emergency response officials are concerned about the danger to both the residents and the rescue workers in a situation where people are fighting to save their properties while vehicle entrances and exits are being sealed behind them.
Opponents note that the Westfield Flood Wall would divert 56th Street river bend flood waters in the direction of the canal. That water could spill over the dip in the towpath near 52nd Street, flooding Rocky Ripple from the east. Such a result would prevent Butler University and Rocky Ripple from realizing containment for the same 100-year flooding events coming directly from the lower elevations of the river.
D. Illinois Street Flood Wall
Opponents note that the high Illinois Street flood walls create a significant visual barrier from Illinois Street north of the bridge, across the canal, and south along the canal on Westfield Boulevard opposite homes north of Chase Bank. This also visually separates the 56th and Illinois commercial center and the Riviera Club from areas northward. While Corps hydraulic studies show that flooding of the unprotected areas south of the wall will not increase because of the wall, opponents note that this configuration contains no components that could help future flood risk reduction for the Butler University/Rocky Ripple Flood Plain or for Butler-Tarkington.
A Different Alternative for Consideration
The Corps initially considered an alternative without a canal flood gate to protect the entire Warfleigh flood plain but thought it more problematic to construct than the Westfield Flood Wall. The City owned the canal at the time of this decision, and so agreed to a canal flood gate that it would own and operate. (Citizens Energy Group now owns the water company and the canal.) Therefore, an alternative without a flood gate never received the rigorous geotechnical and engineering study that might have shown it to be economically competitive with the alternatives that include a canal flood gate.
This 1996 alternative had a flood wall along the river bank at the Riviera Club and between the river and the canal to Canal Boulevard to close the river bend gap. From this point south it used a reinforced right bank of the canal as the flood barrier. (See purple line on map.)
The towpath berm would likely need to be strengthened and widened in places. The top may need to be raised two feet at its dip around 52nd Street. An important question asked by those opposing the flood gate alternatives is what it would cost to transform the berm into a flood barrier suitable for both a 300-year flood plain and FEMA approval to eliminate Warfleigh from 100-year flood plain map. Could a plan be crafted to meet the needs of all the affected neighborhoods and institutions while harming none?
I. Riviera Club
The Riviera Club is in the middle of all options. A flood barrier for the rest of the community works equally well with a wall along the club’s river bank property or a wall completely around its perimeter. Club members should indicate their preference, as there are consequences for either path and ways to reduce the impact of each one.
II. Butler University/Rocky Ripple Flood Plain
The initial 1990s proposal by the Corps for flood risk management included a barrier protecting much of the Butler University/Rocky Ripple Flood Plain. The Rocky Ripple Town Council voted against the proposal because of the impact on some properties. Since that vote, Rocky Ripple residents have elected a new town council that has repeatedly requested inclusion in the flood project.
The Corps process, meanwhile, has proceeded with protection of the Warfleigh 300-year flood plain alone as its focus. Expansion of that focus with a wall and levee around the low, sandy Rocky Ripple flood plain to contain a flood at 2.1 feet higher than the 300-year flood makes little sense hydraulically and financially. However, many Rocky Ripple residents believe that it does make sense to improve flood protection for the Butler University/Rocky Ripple flood plain with less intrusive means for floods of 100-year magnitude and smaller. Reasonable flood risk management plans for both flood plains should be coordinated by the City and committed to simultaneously.
III. The Decision
The Corps and the City must agree on the design of the project. FEMA will make the decision whether to change the 100-year flood plain map. The Corps must be confident the structures meet its standards and that the City will be able to maintain them in perpetuity. FEMA must agree that the structures are appropriate (and maintained) and the Warfleigh trees removed in order to withdraw the area from the 100-year flood plain.
The City must be confident of a flood risk management strategy that will safeguard the vitality of and do no harm to each affected Midtown neighborhood.
William Beranek Jr., Ph.D., of Beranek Analysis LLC, has served in Indianapolis as an environmental mediator since 1975.