Modified Plan for Main Street – A Flood Wall – Partial Demolition – Preserves Tea on Tiber and Phoenix

This proposal presents a major alternative concept plan for Main Street which was seemingly not considered by Howard County in preparing the Five-Year Flood Mitigation Plan: a flood wall along lower Main Street.  This proposal also preserves two of the ten buildings and the facades of up to six others, while increasing the channel capacity and lowering the water levels and velocities on Main Street.

In discussing facades, the Flood Mitigation Plan proposal dismisses the option to preserving facades; it states in one paragraph without any detail: “Another option was explored to remove the backs of buildings that spanned over the channel and were often built years after the original building. By removing the additions, the channel would not have constraints of a building blocking the flow of water to a specific height. Although this option would preserve the facades, the result showed that the water depth on lower Main Street did not decrease significantly.” There is no explanation of the details of these conclusions. What did they really envision in preserving the facades? What variables were included in reaching the conclusion that water depth did not decrease? Some have said that the County did not take into account any upstream mitigation. From the one map, this is hard to discern. However, what is clear is that the County’s proposal does, perhaps disingenuously,  omit one important variable in maintaining facades–the Maryland Avenue diversion tunnel.  How much water remains on Main Street when both options are combined?

The Fire Department has also expressed concerns that facades are unstable and dangerous. Yes, poorly supported facades are dangerous. But did the County consider constructing a new load-bearing wall to support the facade on the land between the channel and Main Street–perhaps only a “mini-building” with not much more than the front windows depending upon the location of the channel? The windows could be used for seasonal displays and could become a tourist attraction.  Alternatively to a “mini-building” the facades could be directly affixed to a flood wall. This would be the case with the “Easton Sons” stone facade at the Bean Hollow.

Another flaw in County Executive Kittleman’s plan to remove the ten buildings is a concern, also expressed by several other people at the Historic Preservation Commission, is that the lack of structures and bridges over the Tiber leaves Maryland Avenue exposed. What will prevent the rushing water from blowing out the culvert, eroding the road, and sending water, cars, trees, and other debris cascading into the historic B&O station? The buildings and bridges over the channel are actually serving to send water onto Main Street and away from the historic railroad station.

Flood Wall with Water Levels
Howard County’s Facade Plan with Flood Wall and Diversion Tunnel Overlayed

Therefore, this proposal removes all of the additions and bridges over the Tiber channel from Caplan’s up to and including Discoveries. Great Panes/Joan Eve, Discoveries, and all but the Easton Sons facade of the Bean Hollow are demolished.  It does not include the removal of the Phoenix Emporium or the historic stone part of Tea on the Tiber. The historic basements of these buildings are thus preserved. The basement would likely be lost if the Tea on the Tiber building were to be relocated.

The Phoenix has also been renovated and is open for business. It is the one building of the ten that is not substantially gutted and/or structurally comprised.  From an economic view alone, demolition of the building is not warranted. It also serves as a focal point for those entering the city from the Patapsco bridge, and frames the streetscape of Maryland Avenue.

Flood Wall with Street Addresses
Flood Wall (teale), Breakwater, and Diversion Tunnel (pink)

This proposal would construct a concrete and steel flood wall either behind the reconstructed buildings or serve as the rear wall itself after the portions over the Tiber channel are removed.  If the wall was constructed at the channel beginning at Caplan’s, it would keep the water from flowing out onto Main Street.  If the wall terminated at say the Tiber Alley bridge the water will flow out onto Main Street. From Caplan’s to this point Main Street would have lower water levels. Yet, the velocity and levels of water would probably be unacceptable where the wall terminates, so the proposal envisions the flood wall continuing to the Phoenix and then wrapping around along Tiber Alley.

The wall will be at least as high as the Phoenix to fully protect the building. A breakwater will probably be required to dissipate the forces of the rushing water and help direct the trees, cars, and other debris away from the Maryland Avenue culvert and diversion tunnel. This would form essentially a Tiber Alley detention area–perhaps 30 feet deep to the bottom of the channel. The breakwater could perhaps be used, like the County’s park plan, for passive use during low water level conditions.

Croatia Breakwater
Example of a breakwater

A section of the wall along Main Street, in perhaps the area of the Tiber footbridge to the Phoenix, would be lower allowing an emergency escape for the water. Like the overflow hole in a bathroom sink, it would keep the detention area from overflowing. The wall and area of Main Street would be engineered to accept this minor flooding. The water levels on Main Street should be relatively low as well as the velocities.

 

Examples of wall waterfalls

Because this Tiber Alley basin would be filing with much of the water that formerly has escaped down Main Street, the County’s proposed Maryland Avenue diversion tunnel will also be necessary.

This proposal meets the County’s goals of reducing the depth and velocity of water on Main Street while increasing the capacity in the channel.  The storage capacity on lower Main Street is dramatically increased over any other proposal. Yet in contrast to the Kittlleman Plan, it preserves two historic buildings. It also preserves the facades of six other buildings and helps to maintain an historic streetscape. In addition, it protects Maryland Avenue and the B&O Museum from flood damage. The unique flood wall might also in and of itself become a tourist attraction.

 

 

 

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