Monday, May 28, 2018

Ellicott City - same actions, same outcomes.

When history repeats itself 20/20 hindsight must become foresight.

After the same scenario played out in Ellicott City not even two years after the first, a stalled front pouring copious amounts of water onto the watersheds of the Hudson and the Tiber, the images became frighteningly similar, in spite of several smaller scale corrective repair measures which had fortified existing water channels with the help of a NRCS grant for streamwalls.
2018 AP photo: the new channel walls held but there was not enough
"conveyance" capacity

As for addressing flooding in a bigger way: As of this month the first batch of retention facilities was in early design but not even phase 1 was funded for construction with  FY 2018 money.  It would take about about three years to construct the facilites. Not even the too narrow culverts crossing Main Street ("pinchpoints") had been replaced. An Ellicott City Watershed Master Plan Open House scheduled to take place three days before the latest flood was postponed "to better address community concerns, further craft technical aspects of proposals, and fine tune plans for implementation."

Most efforts focused on getting businesses back up and running and supporting the rebuild with a marketing analysis, pedestrian improvements and urban design. The SUN reported that Local officials recently said that 96 percent of the businesses were back in operation and more than 20 new businesses had again opened in the Main Street area. One of the businesses which had not returned was a jewelry store which had lost everything in the 2016 flood. It had disposed the items retrieved from a floating vault in a fire-sale and turned the historic Main Street its back for good. The store remained boarded.  Not so the rebuilt Caplan Store, even though its business hadn't returned either and the owner had carefully restored the historic storefront and then converted the former department store into a fitness gym for women.
Caplan Storefront: Totally destroyed again (Police video)

Once again a 500 year precipitation didn't wait for its turn. Before 2011, it had been nearly 60 years since runoff from the Tiber stream produced a flash flood. But in the past seven years, destructive flash floods have hit three times: Tropical Storm Lee in 2011 the summer thunderstorm of 2015 and now the spring flood of 2018. The jeweler probably counts his blessings.The Caplan storefront was ripped out again thanks to its location in a curve where the water and debris rush straight into it and even crashed the entire floor. The storefront posts or the glass had not been fortified in the reconstruction, even though steel reinforced posts and bulletproof glass could still have yielded a historically correct appearance.
The orange dost are "pinchpoints" which haven't been removed since 2016
(December 2017 watershed masterplan presentation)

Of approximately 526 acres of neighborhoods that were assessed by field crews of the watershed study of the Patapsco Heritage Greenway group in 2013, sixty percent (310 acres) of area had no apparent stormwater treatment. Twenty percent (~100 acres) of that had an impervious cover, letting stormwater run off in full and uncontrolled.
The tragic events are, in fact so similar, that copying in an article I wrote in 2016 after the big flood that left old Ellicott City destroyed is still news. Even the County Executive is still the same, it doesn't even look as if this time around he will change his "we must rebuild" tune.  
[Residents and merchants] "are faced with the same daunting task again."
"We will be there for them as we were in 2016," 
Kittleman, 2018
  • There is nothing we can do to stop 6" of rain but we can have impacts on other storms (Kittelman 2016)
The "there is nothing we can do" argument by necessity ultimately results in the abandonment of the historic town in favor of the unfettered and entirely unremarkable development upstream.
Certainly, retreat is one of three options in building resiliency. The traditionally preferred option, fortification, doesn't appear to be very practical in the case of the historic town. Whatever dams, floodgates and elevated structures fortification would require, those measures would almost all run headlong into the core of what makes the town valuable in the first place, historic preservation.
Masterplanning: "We are here" in December 2017
(December 2017 watershed masterplan presentation)

The third option, a multi-prong intelligent approach of taking off the peak of water's destructive power was described in another of my 2016 Ellicott City articles and is essentially the path the watershed masterplan is taking:
The incremental differences  may be in the 5% range for each measure individually. Cumulatively, those improvements may take the wrath out of a 5" per hour rain. Yes, there would still be flooding but incremental differences could be the all deciding differentiator between a catastrophic flood or just a flood.

While old Ellicott City rebuilds, preparation for the next mega rain has to occur now.
However, the masterplan process soon began lacking urgency and it is not clear if even its full execution could have avoided Sunday's flood. Back in 2016 my writing landed me at some meetings of the flood working group. A pretty amazing body of knowledge was soon readily in hand (several key findings are repeated here). Then a msterplan was started. In December of 2017 the County conducted a public meeting about the Ellicott City watershed masterplan which was at the time described to be at the half-point.
The master plan process will help define a comprehensive community-driven vision for rebuilding a stronger and more resilient Ellicott City. (website)
Ellicott City flood 2018
The purpose was to have "conversations" on "emerging recommendations", language that suggests a lack of urgency. It was especially obvious when the presenter from the Department of Public Works addressed the urgent questions of the attending residents and business owners about water retention and pinch point repair evasively or not at all.
The master plan team’s emerging strategy (to mitigate flooding and simultaneously enhance downtown’s urban design) seeks to improve flood water conveyance in the downtown core. The strategy is built around the following goals:
1. Get all of the upstream water to reach Lot D without flowing down Main Street2. Understand impacts and conveyance opportunities from Lot D to the Patapsco (website)
The lead consultant for the plan is the Baltimore landscape architecture and planning firm Mahan Rykiel. A lot of nice ideas about place-making and 'day-lighting" of streams were created. Two weeks ago, the Governor announced that the Federal Emergency Management Agency (FEMA) had awarded the state and county more than $1 million to pay for flood prevention projects for Ellicott City. “This is another important step in the rebirth of downtown Ellicott City,” Governor Hogan said in a statement. “We will continue to work with our federal, state and local partners to help Howard County recover and thrive.”  The Governor won his election in part by demeaning stormwater management fees enable by his predecessor as a "rain tax".

The measures proposed in the masterplan would need much, much more  FEMA money than this grant, and even more time. Time that wasn't allowed as it turned out very shortly thereafter.
Downstream Opportunity sites for water retention and design (Mahan Rykiel)

Changes to surface parking lots (the opportunity sites) will be needed to improve water movement from Lots F to D (and to potentially add a daylit stream, associated greenspace, and pedestrian-oriented "riverwalk").

Before parking spaces are removed in surface parking lots, parking spaces should be added elsewhere.
Phase 1 - Former Roger Carter Site
As a first phase, a temporary surface parking lot at the former Roger Carter site would allow for changes in either Lot F or Lot A 
A hydraulic study prepared after the 2016 storm by the engineering firm McCormick Taylor was refined. The original study included these findings:
  • To catch the water volume that makes the difference between a 10 year and a 100 year flood event in the Hudson Branch watershed alone would require water storage akin to 33 football fields 6' deep.
  • To convey all the water it would take a  12' wide and 8' high storm culvert (which the City of Frederick could build but for which Ellicott City has no space.
  • If the entire watershed were wooded the water arriving at Main Street would be cut almost in half. 
  • If all 23 stormwater ponds in the watershed were not there it would make only an 18% difference for the 10 year storm and 10% in a 100 year storm. 
How much is a 100 year storm? In Maryland's Piedmont around 7" of rain in 24 hours. The storm that hit Ellicott City in 2016 brought just under 6" in only two hours. The tropical storm Lee in 2013 dropped 4.89" in two hours. The May storm of 2018  dumped more than 8" of rain in five hours.
Mahan Rykiel urban design concept for Tiber Alley and B&O Plaza near the
Patapsco River

Ellicott City provides a sad but illustrative tableau of the way how most of humanity deals with the threat of changing weather events. 
Changing climate outruns the sluggish pace in which most societies enact change and continue to put a normal business agenda ahead of the actual menace. 

It will be interesting to see what will happen to the masterplanning process now after this second and even more brutal reminder that time is of the essence. If there will be another public meeting, one can be sure the agenda will be dictated by upset residents and business owners who had been lulled into a false sense of safety and progress.

Klaus Philipsen, FAIA

Also on this blog:
Sidewalks scoured out, buildings undermined once again (Police video)

Wednesday, August 3, 2016

What nearly wiped out Ellicott City and what should be done about it

Ellicott City at Patapsco after Tropical Storm Agnes 1972 (SUN Paper)
I always was in awe when I walked along the banks of the Patapsco River and the remnants of the little mill town Daniels came into view that the river wiped out in the wake of tropical storm Agnes (luckily it had already been condemned and was vacated).
Agnes turned River Road into a trail and was never opened to traffic anymore, here and there lurked a rusting auto wreck in the brush.

Before the Grist Mill trail was constructed a few years back, one could also spot an axle from a rail-car that had once toppled off the rails high above the river; the raging river had washed out the track-bed. The Patapsco rose high enough to reach Caplan's department store in Ellicott City and destroy the bridge into town. Such was the power of the river.

The streams feeding into the Patapsco (historic map)
This time was different: the danger for Ellicott City came not from the river below but from the hills above. The AME church on Main Street located west and above the old fire house is way above and far away from any water that ever came from the Patapsco. Still, the church lost its entire embankment on Saturday night.

Each of the tributaries that feed into the little Tiber stream that runs parallel to Main Street had already become a raging torrent before reaching the Tiber. That totally overwhelmed its riverbed which is partly covered up by buildings. So the Tiber began running down Main Street instead, turning the picturesque historic street into a mountain river which carried mud, logs and cars into storefronts and finally inevitably into the raging Patapsco.

What caused this and what should be done to avoid it in the future?
AME Church on upper Main Street
(Google Streetview)

From what is known to date, the causes were
  • a stalling weather-front that carried copious amounts of moisture and let out more water in one hour than any previous rain event in the area. That may or may not have to do with climate change; at any rate, it is suspicious that two storms that, according to past statistics, would be 100-year storms happened within a few years. 
  • The other contributing factor is development. Denuding, shelving and paving over the steep slopes around Ellicott City is an ongoing development pattern fueled by the incredible growth that the fastest growing jurisdiction in Maryland is experiencing. 
  • Even the most progressive stormwater management techniques don't deal with 5" of rain in one hour and will overflow, doing nothing to protect the valleys below. Although a forested slope would release some of an extreme downpour as well, it wouldn't be nearly as much.
  • Stormwater pond at Burgess Station: Blown out (Photo: Philipsen)
  • Lastly, there is circumstantial evidence that at least one totally failing stormwater retention pond released all its content in a sudden burst into the creek about 30' below. That may have contributed to the wash-out of the AME church and/or created some type of flood wave with a surge of energy all the way down Main Street
Marsha McLaughlin, the former Howard County Planning Director suggested that Ellicott City shouldn't be rebuilt as it was. 

Rebuilding was precisely, what the County Exec Kittelmann had vowed in the first hours after the destruction. 

Not rebuilding right into the danger zone is normally wise. However, in this case, this would mean abandoning all of historic Ellicott City. This flood endangered almost the entire town.
The matter had been on the radar for some time. Early 2015 County Exec Kittelman convened a Historic Ellicott City Flood Work Group which published a report in November of last year. Its final words show that while accurate, the efforts need to be ramped up far beyond what was included as short and mid-term action.
Climate change could make future flooding more frequent and larger in scope. Development in the watershed has contributed to the flooding danger and this needs to be considered if proposals for new development occur. We hope this report will help prevent loss of life and damage to property in the place where we live, work and recreate, Historic Ellicott City. (Work Group Report)
location of the pond at Burgess Station (Graphic Elliot Plack)
Likely the best solution for protecting old Ellicott City from future floods resides above the town, near the top of the valleys leading into the town center, in many decentralized places that either prevent or catch run-off long before it gets destructive. A sustainable effective solution is less likely to be one or two heroic structures in the low areas such as under the town's parking lots D or F as suggested in the report. 

Contours and pond location at Burgess Station (Graphic Elliot Plack)
Facilities need to be constructed that are large enough to hold those massive rain bursts long enough to avoid destruction and overflows. Since so much of the area is developed, those structures would probably have to be underground. These measures are not rocket science and have been used and refined around the world, either as surface measures such as dams, retention ponds or water parks (Rotterdam) or as underground measures in cavernous underground storage tanks or large diameter pipes.
There appears to be little that can be done along Main Street itself except for protection against water backing up from the Patapsco. 

Klaus Philipsen, FAIA

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