Blog‎ > ‎

The Ellicott City Watershed

posted Dec 28, 2016, 3:58 PM by Lori Lilly

In Howard County, MD, we have all been hyper-focused on Ellicott City since the 7/30/16 flood that devastated the town, community, residents and businesses. Amazing destruction, terrible and scary videos, businesses destroyed and residents evicted. The town is left on crumbling infrastructure, recovery is under-way, but it will take a long, long time. People are sad and angry and rightly asking why and how this happened. I don’t have any secret answers, but I can offer my own perspective as someone that has been working on this issue from both a professional and volunteer capacity since the 2011 flood. In 2011, I led the development of the Tiber Hudson Subwatershed Action Plan. We looked for both water quality and water storage projects in the watershed with the goal of mitigating for polluted stormwater runoff as well as providing more flood storage capacity. During that same timeframe, I became the first volunteer chair of the Ellicott City Partnership’s Clean, Green and Safe Committee. In fall, 2015, I was asked to join the Ellicott City Flood Workgroup. Out of my own growing personal interest in the issue, I put together documents and led some initiatives over the past 5 years:

  • timeline of activities, as I knew them, from the 2011 flood – Fall 2014, during the time when I was then working at the Center for Watershed Protection, trying to get some projects going in the watershed and offering volunteer support to the now defunct Ellicott City Flood Solutions Group.
  • flood action plan, represents my own views only, and was shared with elected officials, Dept of Public Works, the Ellicott City Flood Workgroup, whoever would listen.
  • flood safety workshop for the public.
  • flood preparedness video, proudly aired at one of the Wine Bin movie nights summer, 2016. It will air there again!
  • Advocated to the County Council and County Executive and then implemented a regular debris maintenance program in the Ellicott City channels with the READY program.  (I can’t prove that the debris maintenance helped in this last flood without doing some Star Trek alternate reality type stuff, but the channels were clear a month before the 7/30 event by my own survey, so I can only hope that it helped things from being worse than they could’ve been.)

Important documentation from the County to note includes:

  • Case Study put together after the 2011 flood.
  • Tiber Hudson and Plumtree Stream Corridor Assessment completed after the 2011 flood that documents wall failures, debris blockages, erosion and constriction points.
  • Hydrologic and Hydraulic Study completed after the 2011 flood that documented conditions during the 2011 flood and assessed whether adding upstream retention and/or increased conveyance would help with the flooding problem – the study determined that those measures would not have appreciably decreased the damage caused by the 2011 flood.

Unfortunately, Historic Ellicott City was founded and built in a floodplain – the floodplain of the large Patapsco River and the floodplain of the Tiber Hudson subwatershed to the Patapsco. Also unfortunately, this watershed, like pretty much all of the watersheds in the region, is broken. Old development, that development built prior to when our current stormwater management standards were put into place, is a large culprit for eroded streambanks, in-stream sedimentation and poor water quality. Most of the development in the watershed occurred prior to 2003 and this can be seen by looking at historic aerial photographs available from Howard County’s Interactive GIS map. Without having these layers available to me in a GIS format, I used some rudimentary drawing to replicate the watershed boundary on historic aerial photography. You can see here that a large portion of the watershed was already developed prior to 1980 and that we then saw more development occur prior to 2002, which still would have been prior to when current stormwater management regulations were put into place. In terms of watershed management, we need to focus on stormwater retrofits of existing large impervious surfaces and stormwater pond retrofits of the older ponds built in the ’90s. We also need to determine if there is a storm that we can actually feasibly manage with those (retrofitted) practices, because managing 1″ won’t help us and managing 100 yr will not help much either, so will something in the middle work, at least partially?  What does it mean for the stormwater management to work, for us, in our situation? Let’s talk about this, community.

I’m also pretty curious about what the current and former big thinkers at the Center for Watershed Protection think about this.  After all, the organization is a leader in watershed management, had some early fundamental years in the historic district, shared many a good idea and bonded friendships at the Judges Bench, and received the “upstairs discount” from Dave at the Wine Bin…the same Dave stranded in a cherry tree in Lot F during the 7/30 flood(!)…Let’s utilize this opportunity to put theory into application!

The Tiber Hudson watershed is also largely built out – the remaining land available for development would be on steep slopes and headwater areas. Nevertheless, new development is planned in the watershed. My personal opinion is that even if this new development goes in with updated stormwater management, that stormwater management will never be able to do as good of a job as the existing forest cover. Engineers may argue otherwise but I’m pretty sure that at the very least, we won’t see a forested system fail the way the Burgess Mill redevelopment stormwater management systems failed during the 7/30/16 flood.

In Howard County, MD, we have all been hyper-focused on Ellicott City since the 7/30/16 flood that devastated the town, community, residents and businesses. Amazing destruction, terrible and scary videos, businesses destroyed and residents evicted. The town is left on crumbling infrastructure, recovery is under-way, but it will take a long, long time. People are sad and angry and rightly asking why and how this happened. I don’t have any secret answers, but I can offer my own perspective as someone that has been working on this issue from both a professional and volunteer capacity since the 2011 flood. In 2011, I led the development of the Tiber Hudson Subwatershed Action Plan. We looked for both water quality and water storage projects in the watershed with the goal of mitigating for polluted stormwater runoff as well as providing more flood storage capacity. During that same timeframe, I became the first volunteer chair of the Ellicott City Partnership’s Clean, Green and Safe Committee. In fall, 2015, I was asked to join the Ellicott City Flood Workgroup. Out of my own growing personal interest in the issue, I put together documents and led some initiatives over the past 5 years:

  • timeline of activities, as I knew them, from the 2011 flood – Fall 2014, during the time when I was then working at the Center for Watershed Protection, trying to get some projects going in the watershed and offering volunteer support to the now defunct Ellicott City Flood Solutions Group.
  • flood action plan, represents my own views only, and was shared with elected officials, Dept of Public Works, the Ellicott City Flood Workgroup, whoever would listen.
  • flood safety workshop for the public.
  • flood preparedness video, proudly aired at one of the Wine Bin movie nights summer, 2016. It will air there again!
  • Advocated to the County Council and County Executive and then implemented a regular debris maintenance program in the Ellicott City channels with the READY program.  (I can’t prove that the debris maintenance helped in this last flood without doing some Star Trek alternate reality type stuff, but the channels were clear a month before the 7/30 event by my own survey, so I can only hope that it helped things from being worse than they could’ve been.)

Important documentation from the County to note includes:

  • Case Study put together after the 2011 flood.
  • Tiber Hudson and Plumtree Stream Corridor Assessment completed after the 2011 flood that documents wall failures, debris blockages, erosion and constriction points.
  • Hydrologic and Hydraulic Study completed after the 2011 flood that documented conditions during the 2011 flood and assessed whether adding upstream retention and/or increased conveyance would help with the flooding problem – the study determined that those measures would not have appreciably decreased the damage caused by the 2011 flood.

Unfortunately, Historic Ellicott City was founded and built in a floodplain – the floodplain of the large Patapsco River and the floodplain of the Tiber Hudson subwatershed to the Patapsco. Also unfortunately, this watershed, like pretty much all of the watersheds in the region, is broken. Old development, that development built prior to when our current stormwater management standards were put into place, is a large culprit for eroded streambanks, in-stream sedimentation and poor water quality. Most of the development in the watershed occurred prior to 2003 and this can be seen by looking at historic aerial photographs available from Howard County’s Interactive GIS map. Without having these layers available to me in a GIS format, I used some rudimentary drawing to replicate the watershed boundary on historic aerial photography. You can see here that a large portion of the watershed was already developed prior to 1980 and that we then saw more development occur prior to 2002, which still would have been prior to when current stormwater management regulations were put into place. In terms of watershed management, we need to focus on stormwater retrofits of existing large impervious surfaces and stormwater pond retrofits of the older ponds built in the ’90s. We also need to determine if there is a storm that we can actually feasibly manage with those (retrofitted) practices, because managing 1″ won’t help us and managing 100 yr will not help much either, so will something in the middle work, at least partially?  What does it mean for the stormwater management to work, for us, in our situation? Let’s talk about this, community.

I’m also pretty curious about what the current and former big thinkers at the Center for Watershed Protection think about this.  After all, the organization is a leader in watershed management, had some early fundamental years in the historic district, shared many a good idea and bonded friendships at the Judges Bench, and received the “upstairs discount” from Dave at the Wine Bin…the same Dave stranded in a cherry tree in Lot F during the 7/30 flood(!)…Let’s utilize this opportunity to put theory into application!

The Tiber Hudson watershed is also largely built out – the remaining land available for development would be on steep slopes and headwater areas. Nevertheless, new development is planned in the watershed. My personal opinion is that even if this new development goes in with updated stormwater management, that stormwater management will never be able to do as good of a job as the existing forest cover. Engineers may argue otherwise but I’m pretty sure that at the very least, we won’t see a forested system fail the way the Burgess Mill redevelopment stormwater management systems failed during the 7/30/16 flood.

The remaining green spaces should be conserved and protected. No, we can’t take away the right of a private property owner to develop his/her property if they are planning to follow all the rules. But we’re talking about a relatively small area of the county – 3 square miles of the County’s total 253 sq miles, and even less if we were just talking about the Hudson Branch subwatershed that includes residential homes in the floodplain. How can we incentivize protection of the remaining green areas? Can the County buy the land? How about an impervious cover ordinance? Howard County’s 2013 Flood Mitigation Plan talks about some of these exact measures – Goal 5, “The intensity of development in the County and the fact that it is landlocked makes it more prone to flashfloods since water does not have a place to flow to;” Action 5, “Consider developing an Impervious Surface Ordinance for the County that encourages the reduction of newly installed impervious surfaces or offsets the impacts of these surfaces in the County.” Something for our elected officials to consider. They might also consider following a model similar to Montgomery County’s Special Protected Areas, whereby “the developer must follow strict requirements throughout the project in order to reduce the threat to these resources and features.”

But much needs to be done in the historic district. The stream channel walls, many partially or fully supporting actual structures, are failing at a rapid pace. I conducted a stream survey on 8/4/16 after the 7/30/16 flood and documented eight new failing or failed walls from what I could safely access – this is in addition to the many walls that had already failed. The County has been working on addressing the walls, most recently though an inventory of their current status (i.e., extent of degradation), and found many in poor condition. Of course that inventory was before the flood and much has since changed… Repairing, restoring and re-building the channel walls is of utmost importance, and will be extremely difficult esp. in the business part of town due to very challenging access for heavy machinery.

One thing on our side with this whole problem is the relatively small size of the Tiber Hudson watershed. This really limits and focuses our actionable footprint. That being said, our work and rebuilding efforts are made that much more difficult due to something more out of our hands – climate change, and predictions of increased flooding and storm intensities. We simply need to be prepared for flood events – as individuals and as a community. This might mean that when re-building downtown, we think about ways that we can safely overflow floodwaters. Perhaps some businesses only operate from the second floor to allow for conveyance on the first floor. Bentztown Spring Park in Frederick is an example, though on a larger scale, of how the City reclaimed the floodplain.

Frederick
The park serves as a recreation area for the majority of the time but, during storms, it is able to serve as a floodway to carry floodwaters. Can Ellicott City do something like that? We are constricted in a granite ravine so that makes the job pretty hard, but let’s get some creative firms thinking on it, yeah?  We have an additional challenge of getting the Tiber Hudson floodwater out of town while the Patapsco is coming in – it doesn’t seem like underground conveyance will work.  See this article from the National Weather Service that says water from Ellicott City’s watershed met the Patapsco at the 8100 block of Main St.  What turbulent meeting that must’ve been…

We need a lot of things to fix this problem. We need to be honest with ourselves about storms we can feasibly manage in the watershed. We need to repair and re-build the failing channel walls. We need to address the eroding streambanks – stabilize them and manage invasive plants like Japanese knotweed that is rapidly spreading. We need dedicated staff that will lead the charge in writing grants and facilitating conversation.  We need to be prepared for the inevitable, and educate those that come to town about what to do if there is a flood while they are dining and shopping. We need to figure out how to convey floodwaters through town in a way that minimizes damage to property and of course loss of life. We will certainly need to look into the existing warning system and see how that can be improved. And more, lots and lots to do.

Finishing up this past week with the READY crews cleaning debris and trash out the channels, we came out of the stream after working all day in the 100+ degree heat, wallowing in our sweaty waders, dirty, smelly, thirsty and having touched all manner of nasty things, only to be greeted by two little kids and their Free Lemonade stand.  We could not have been more heartened and uplifted by so small a thing.  I love this little town with all the rest and believe we can re-build in a way to make it that much stronger.

DSCN2631

#ECSTRONG

Comments