Timeline of a Watershed

By Patrick Fitzgerald - City of Gaithersburg Stormwater Project Manager

November 15, 2021

The Chesapeake Bay Watershed

Gaithersburg's streams feed into the largest estuary in the United States. The Chesapeake Bay's drainage basin spans six states and the District of Columbia, and together this community shares a great responsibility to restore our watershed for future generations. Before understanding what we can all do to help in those efforts moving forward, we should first learn from the past.

The "Beginning"

Approximately 35 million years ago, a meteor collision resulted in an enormous crater which would eventually help form the Chesapeake Bay. There are countless geological events from that point on that gradually contributed to the Bay as we know it today, but this impact can arguably be thought of as its birth.

Human Reliance on the Bay

Humans are believed to have first inhabited the Chesapeake Bay Region about 11,500 years ago. At that point, the Delmarva Peninsula was finally formed and served as a barrier to help protect a flourishing ecosystem that provided abundant resources for people to live off of. Fishing methods have changed drastically, but people have continued to rely heavily on the Bay for sustenance throughout the years.

Population Growth

Humans have only been in the area for about 0.03% of the Bay's 35 million-year life so far. In that "brief" moment, humans have managed to leave their footprint by colonizing, industrializing, and expanding exponentially. Over the last 70 years alone, the population in this watershed has more than doubled according to the Chesapeake Bay Program .

The Era of Development

In order to sustain a rapidly growing population, land development had to speed up to match the pace. Technological advancements over the past century made that pace of development possible.

Below is a look at how the landscape of Gaithersburg has evolved in the past 70 years.

Impervious Area

The human "footprint" left behind during this era comes largely in the form of impervious area. Grassy meadows and forests have rapidly been converted to hard surfaces that prevent rainwater from infiltrating into the groundwater table. The first asphalt road in the U.S. was paved in 1870 according to historians. About 150 years later, over 4 million miles of roads cover this Country. The City of Gaithersburg is about 44% impervious as of 2021.

Why it Matters: Stormwater Runoff

Impervious area is so critical to the health of the Bay because it presents two major issues: flooding and water pollution. These surfaces significantly increase the rate in which stormwater runoff is able to travel, meanwhile serving as a conduit for pollutants such as oil and debris dumping straight into the nearest stream if left unchecked. Per the Chesapeake Bay Foundation :

Only 10 to 20 percent of rain that falls in forests, fields, and other natural areas runs off, with the rest absorbed by soil and plants.
Close to 100 percent of the rain that falls on concrete and other hard surface produces runoff.
An inch of rain falling on an acre of hardened surface produces 27,000 gallons of runoff.

The City's Stormwater Program conducts regular inspection of the City's stormwater facilities and infrastructure. Issues are found regularly and can sometimes be remedied quickly, but resolving the root causes of the issues takes much more time, money and collaboration between jurisdictions and the community.

Left Photo - CCTV image of debris-filled pipe. Middle Photo - Failing outfall pipe in stream embankment. Right Photo - Channel erosion downstream from a large pond's emergency spillway.

The local issues across the Chesapeake's watershed add up to more global concerns. As impervious area continues to rise, so do sea levels and the frequency of which heavy storm events are occurring. The harmful effects from untreated impervious area are amplified with the rapid change of climate. The infrastructure that was installed in the past was not designed with the realization of how drastic these changes would be.

Left Photo - The last house remaining on Holland Island in the Chesapeake Bay before it was completely submerged. Right Photo - A property in Gaithersburg located in a FEMA 100-year floodplain zone.

Stormwater Management

Although these issues are daunting, there are several methodologies to tackle them that have been constantly evolving over the last several decades. The Maryland Department of the Environment (MDE) breaks stormwater management best management practices (BMPs) down into four main design eras based on when major regulation changes occurred.

Prior to 1985

Before the implementation of Stormwater Management regulations in Maryland, very few BMPs existed in our surrounding area. Gaithersburg does have a few large ponds that were installed prior to formal regulations.

Between 1985 and 2002

In this timeframe, BMPs were required by Maryland's first Stormwater Management Law. The Law was passed in 1982 and was implemented in 1985. The requirements focused primarily on flood control, which was done most commonly with large ponds. These ponds store heavy storm events with the use of a carefully designed control structure with an orifice which lets water flow out at a safe rate.

Map of Washingtonian Center (Rio) from 1998

Between 2002 and 2010

The Maryland Stormwater Law was updated in 2000 and implemented in 2002. This update continued a focus on quantity control, but also introduced formal requirements to address the growing concerns for water quality. BMPs were required that would not only detain large storms, but would also reduce pollutants in runoff through methods like filtration.

Underground Vault with Filter Cartridges

2010-Present

Another update to the Law came about through the Stormwater Act of 2007, which was implemented in 2010. The goal of this Act was to install green infrastructure, which MDE refers to as Environmental Site Design (ESD). The Act defines ESD as “…using small-scale stormwater management practices, nonstructural techniques, and better site planning to mimic natural hydrologic runoff characteristics and minimize the impact of land development on water resources.”

Even with decades worth of BMPs in the ground, about 48% of the City's 2,932 acres of impervious area do not drain to a creditable water quality treatment facility. The City's target is to reduce its untreated impervious area by 20% by 2025.

On Left: Total Impervious Area. On Right: Treated Drainage Area Overlay Shown in Blue.

Bridging the Gap

Even after 2025, there is still a long way to go. How do we reach a green future with a fully restored watershed?

A fully restored watershed, one that truly mimics natural hydrology while humans are thriving sustainably, will take a very long time to achieve. The City's Stormwater Program is actively working on projects and planning out long-term strategies for the next target beyond 2025. Even if the Program had the funding and bandwidth to immediately install enough green infrastructure to treat every square foot of impervious area in the City, much of that area is privately owned. The City can offer incentives and education programs to help encourage small changes and speed the process along, but the last steps of a full restoration process will involve waiting on these types of properties to be redeveloped to incorporate stormwater management.

Residential Properties

At 507 acres, this is the largest category of untreated impervious area in the City. There are large expanses of residential neighborhoods that were developed prior to water quality requirements and will likely not be redeveloped under current regulations anytime soon. Still, there are programs in place that incentivize residents to voluntarily install things like rain barrels and conservation landscaping, and these are great ways for people to chip in to make a difference in the short-term.

Bird's Eye View of Untreated Residential Area

Closer View of Untreated Residential Impervious Area

The City is also planning to work with Common Ownership Communities to perform BMP retrofits to some existing dry ponds to provide more current water quality treatment. This can still be a somewhat lengthy process with easements, agreements and policy changes, but it is initiating active restoration rather than passively waiting on properties to be redeveloped.

Drainage Areas for Potential HOA Dry Pond Retrofits

Commercial and Mixed Use Properties

There are approximately 291 acres of untreated impervious area in the City located on commercial and mixed use properties. Similar to the residential property owners, there is little to do other than wait on commercial redevelopment to play out. However, these types of properties do tend to turn over slightly quicker than residential properties, and there has been a relatively steady flow of commercial redevelopment since water quality regulations have been in place.

Roadways

Roadways make up 457 acres of the City's untreated impervious area. Despite the fact that roads are owned and maintained by several different types of entities (City, County, State, residential, commercial, etc.), they can easily be lumped into one category for the sake of this topic. Most existing roads are congested with a variety of utilities, sidewalks, narrow shoulders, and other infrastructure to compete with. Future roads are being designed with more emphasis on providing adequate space for stormwater, but retrofitting opportunities are very challenging.

City-Owned Properties

Out of the 1,402 acres of untreated impervious area in our City's boundary, only about 26 acres are located on City-owned properties. With that said, this is where the bulk of the City Stormwater Program's completed and planned projects are located. Having reviewed the complications with parcels the City does not own, it is clear to see why more immediate efforts are focused on the parcels the City can actively control.

Although there isn't a comparatively great deal of untreated impervious area on City land in need of restoring, sites are strategically picked that can intercept runoff from additional parcels to provide additional treatment for off-site impervious area. This can be done by adding a new BMP, or by retrofitting an outdated or failing BMP into a current, creditable facility.

City-Owned Dry Pond Intended to be Retrofitted

City land also comprises an extensive stream network. Many stream reaches are not able to withstand the increasing flow rates from developed areas and the results can be extremely harmful to the health of the Bay. Treating all of the upland impervious area will be a long-term process, and the need for stream restoration projects can often be too urgent to wait for that process to unfold. Looking at the area draining to these projects helps put their magnitude into perspective.

Area Draining to Completed and Planned Stream Restoration Projects

Below is a quick tour of the stream restoration projects completed by the City in the last five years.

01 / 04

West Deer Park

Completed in 2016 - 338 linear feet of stream channel restored.

Lakelands

Completed in 2020 - 980 linear feet of stream channel restored.

Orchard Ridge

Completed in 2020 - 870 linear feet of stream channel restored.

Watkins Mill and Travis Avenue

Completed in 2021 - 2,347 linear feet of stream channel restored.

Epilogue

It's been a bumpy road so far, but there are plenty of reasons to be optimistic about the future of the Bay. It is encouraging to be a part of a community that is so motivated to make a difference. Passing our knowledge down to the next generation and reminding them of the mistakes of our past makes room for endless possibilities. There are already signs that our ecosystem is starting to make a comeback despite the human population continuing to grow, which shows that maybe the two are finding a way to coexist. Hopefully, people will look back and see our actions now as a positive turning point in the Bay's fascinating timeline.

Additional Resources

If you still want to learn more about the Chesapeake Bay, the City of Gaithersburg Stormwater Program, and what you can do to start restoring our watershed today, please check out the links below.