Friday photo: Cranes at the Wharf, from spring into summer

Cranes at the Wharf, 10 July

10 July 2015.

Cranes at the Wharf

15 March 2015.

I’ve been trying out a faux-time-lapse-photo series of the ongoing construction of the Wharf, the mega-project just a few blocks down the street. The photos are taken from the Case Bridge, under the “L’Enfant Promenade, Keep Right” sign.

Since the lower photo was taken in March, the piers have been substantially completed, thousands of foundation piles have been nailed into the ground, excavation has been completed for the sitewide underground parking garage, and some of the first structural supports. Since the site is just about at sea level, substantial pumping will continue to keep seawater out of the hole until the foundation is complete. Two of seven tower cranes have arrived on this side.

Also, be sure to check out my posts at Greater Greater Washington. I used to crosspost all of them, but haven’t done so as much lately.

The Silk Road’s detour to the Washington Channel

The first post in the watershed series mentioned that Morus alba (white mulberry) is a common invasive understory tree found at the edges of lawns along the Washington Channel, particularly along the unmown verge beside the fences that ring East Potomac Park’s recreation facilities. Given a chance, these shrubs will grow into a smallish tree of up to 15 meters, with a peculiar combination of lobed leaves on young shoots and heart-shaped leaves on older shoots. Its copious blackberry-looking fruits , which can disperse an estimated 20 million seeds per tree, make a convenient food source for birds and maybe humans — or else they leave a sticky purple mess on the walkways below.

But wait, mulberry? Isn’t that what silk is made from? How did that end up here?

White mulberry
What is this weed, and what does it have to do with the Opium Wars, Jefferson family wedding gowns, and deforestation in Ontario?

Silk production, or sericulture, was invented in China at least 4,000 years ago; legend says it was discovered by a princess who was strolling through the woods with a cup of hot tea. Young mulberry leaves are fed to silkworms, which spin silk threads around their cocoon as they metamorphose into moths. The cocoons are collected, boiled, and the threads are spun into fiber. China still accounts for most of the almost one million hectares (2.5 million acres) of mulberry under cultivation worldwide, according to the FAO, largely for silk but also for forage, wood, and even biofuel.

Yet sericulture (silk cultivation) requires that both mulberries and silkworms thrive in tandem. Mulberries obviously have adapted well enough to the local climate; thousands of years of domestication has selected for robust and easily grown varieties. The silkworms are a different story: they’ve been raised indoors for thousands of years, and thus have evolved into a very narrow ecosystem — they don’t even survive in the wild anymore, and require an exacting temperature range of 73-84° F, with high humidities, in order to thrive.

Silk was long one of the world’s most coveted agricultural products, and for centuries the world went to astonishing lengths to procure it from China.* Starting all the way back in Jamestown, Virginians attempted to get a cut of this lucrative trade by manufacturing silk: it seemed an ideal fit for the area’s warm climate and then-remote location, and potentially valuable both for the colonists and for British weavers. Yet while Virginia hews a bit closer to such temperatures than England, it isn’t exactly a room-temperature silkworm paradise. So while the robust mulberry thrived, fragile silkworms brought to Virginia didn’t, and instead Virginians profited off the native tobacco plant.

Mulberry Row

Thomas Jefferson’s family attempted silk cultivation at Monticello, and the results are telling. Above is “Mulberry Row,” the remnant of a lane lined with mulberry trees and, once upon a time, several buildings where slaves and other laborers did much of the work of the plantation. Obviously, the mulberry trees have done okay over the years — outlasting the buildings, for instance. The silkworms, though? Not so much. In 1811, Jefferson jokingly wrote to his granddaughter Cornelia,

your family of silk worms is reduced to a single individual that is now spinning his broach. to encourage Virginia and Mary to take care of it, I tell them that as soon as they can get wedding gowns from this spinner they shall be married. I propose the same to you that, in order to hasten it’s work, you may hasten home; for we all wish much to see you.

For what it’s worth, neither Mary nor Cornelia ever married, although I doubt her silkworm colony’s failure to generate enough silk for a wedding gown had much to do with that.

Silk was so valuable that Americans couldn’t be dissuaded by the industry’s failure in Virginia. Silkworms, as mentioned above, are fickle and highly adapted to the methods of Chinese sericulture; they feed almost exclusively on Morus alba, which as mentioned grows quite vigorously on Chinese farms. Eastern North America has a native variety of mulberry, Morus rubra, an understory plant suited to the area’s deep forests, but the silkworms rejected M. rubra feed.

Instead, colonists planted several Chinese mulberry varieties in hopes of keeping their silkworms happy. Colonial-era botanist William Bartram, in his travels through the South, noted dozens of instances of M. rubra but only one of M. alba trees — at a plantation near Beaufort, S.C. that was attempting sericulture (digitized book, pg. 308; location surmised between present-day Jacksonboro, S.C. and Savannah, Ga.). Later, Connecticut implemented various subsidy schemes, even including a cash bounty on planting Chinese mulberry varieties, and eventually succeeded at building a small silk industry in the 19th century.** (The Morus multicaulis mentioned in the Mansfield article is now recognized as a variety of M. alba.)

In the intervening centuries, the invasive M. alba has far outcompeted native M. rubra on its home turf: M. alba has spread much of the contiguous United States except for the desert Southwest, high plains, and taiga forest, and pushed M. rubra to endangerment in Connecticut, Massachusetts, and Ontario. Not only have widespread planting efforts like those in Connecticut spread M. alba far and wide, but it’s a tree that’s been honed by centuries of breeding for vigor, with a “high growth rate and great adaptability to adverse environments,” according to the Global Invasive Species Database: “M. alba and hybrids were evaluated to be consistently more fit than the native M. rubra in a laboratory study.” M. alba hybridizes with, and spreads root diseases, to M. rubra. Widespread deforestation and urbanization in eastern North America opened up countless opportunities for sun-loving, early-successional species like M. alba, while concomitantly destroying the deep shade that M. rubra adapted to.

* As a descendant of Cantonese merchants, perhaps I should be glad that these experiments failed? Oh, the complicated webs that history weaves for us!
** The mild success found in Connecticut indicates that perhaps it was less the climate, but Virginia’s lack of capital for indoor silkworm warms, that doomed the early industry.

This semester, I’m taking a Natural Resources class through Virginia Tech about understanding local watersheds, wherein I’ll be researching and posting knowledge about the Washington Channel. You can explore the other watersheds that my classmates are investigating over at the class blog’s page. Other posts in this series can be found using the tag watershed.

Washington Channel: more a conduit than a stream

While Washington Channel is known for its fishing, it’s not because it’s a particularly inviting habitat for fish species. Instead, its unique flow pattern of imported water make it a “trap” for fish swept upriver by the tides, and as such it sees fish species that aren’t typically found in other local waters — which, oddly, makes it popular among anglers.

Washington Channel & Tidal Basin at high tide

The most productive and diverse habitat in most waterways–the shorelines–are along the Washington Channel entirely armored with concrete. Beyond those concrete walls are monocultures — either more concrete or lawns, rather than on-shore wetlands. Between the walls, the constant scouring effect of the Channel’s twice-daily flush keeps the Channel relatively deep, so there are scant near-shore wetlands: the central channel is kept at least 9-14 feet deep for navigation purposes, but the entire channel ranges from 3-26′ deep. (The Tidal Basin is a bit more inviting to life, since it’s shallow [5-7′ throughout, average depth of 6.5 ft.] and a bit more placid.) The shallow-water ecosystems at the water’s edge, which combine sunlight, warmth, nutrients, and shelter, are largely absent along both. The Channel is, in effect, a concrete canyon.

DC Fire Rescue Boat and Army War College

This canyon isn’t very resilient, either; it can easily flood, as there’s nowhere for water to go when the river rises — or even for the wake from powerboats to do anything other than echo off the walls.

Washington Channel & Tidal Basin at high tide

The shore edge’s armor has started to degrade, though: a combination of higher water levels, subsidence by the marshy soil, inevitable concrete failure, and erosion means that some areas behind the seawall are now almost permanently wet. Some wetland species might start to colonize these damp pockets, although lawnmowers will probably thwart their progress.

Some of the shallower parts of the Washington Channel have demonstrated potential as rich habitat, though. A stretch of older seawall along Fort McNair, beginning in a small lee behind the Titanic Memorial, is a comparative haven for aquatic vegetation and fish. At one point, there was a 10-20′ wide band of submerged aquatic vegetation (SAV) off the fort’s shore — which, according to the NOAA navigation charts, is the shallowest part of the Channel at just 2-5′ deep. These underwater meadows provide valuable fish habitat, particularly for anadromous (half-ocean, half-estuary) species that spawn there before returning to the saltwater estuary downstream.

Even as Potomac River water quality has improved, habitat quality in Washington Channel remains poor. The quantity of SAV (much of it invasive hydrilla, which was still better than nothing) grew substantially in the 1990s, alongside large fish populations.

ecosystem health Wash Channel

Sadly, major rains throughout 2003 — when the Potomac carried more than 3X as much water as in the drier years 1999-2002, and twice its annual average (MWCOG/VT PDF, pg. 32-33*) — led to severe sediment and nutrient overload throughout the Potomac ecosystem, and thus to large algae blooms in 2004. These two years’ trials devastated established SAV in the upper Potomac estuary, including in Washington Channel, and so far neither plant nor animal life seems to have recovered.

Second chances: improving habitat in channelized waterways

While the Washington Channel may be the local champion for having the least natural stream banks, it’s sadly far from the only such watershed nationally. Perhaps the worst example of an “imprisoned river” is the Los Angeles River, almost all of whose banks were paved back in 1938.

Yet nature does abhor a vacuum, and so if you provide adequate habitat (as the Channel did for those few lovely years around 2000), an ecosystem will soon blossom. In Chicago, the Friends of the Chicago River built a “floating fish hotel” to provide a smidgen of near-shore-wetland habitat within downtown’s urban canyon, and plans to significantly expand upon this experiment in the near future.

* Incidentally, to update something I wrote earlier about Western and Eastern water systems, the Colorado River’s pre-diversion annual flow was 50% larger than the Potomac’s average flow (at Little Falls) today. It would rank among the largest Eastern rivers, like the Hudson or Susquehanna. This great map from the Pacific Institute clearly shows my earlier point: the East is well-watered indeed.

** 2018 update: a SAV planting program has succeeded in dramatically increasing SAV in the upper Potomac estuary since 2013, and in increasing juvenile bass populations. Floating “fish hotels” have been added next to the 7th St. “recreation” pier at the Wharf.

This semester, I’m taking a Natural Resources class through Virginia Tech about understanding local watersheds, wherein I’ll be researching and posting knowledge about the Washington Channel. You can explore the other watersheds that my classmates are investigating over at the class blog’s page. Other posts in this series can be found using the tag watershed.

Fresh policies will freshen the flow into the Washington Channel

Yesterday, I wrote about the numerous storm drains that currently dump polluted water directly into Washington Channel. The District of Columbia recently adopted some of the nation’s most stringent and innovative rainwater policies, and the Washington Channel watershed stands to significantly benefit as plans and projects adapt to these new policies and incorporate state-of-the-art practices in green infrastructure (GI). The Natural Resources Defense Council’s “Rooftops to Rivers” report give DC’s new policies a high rank (just behind Philadelphia) among their “Emerald City Criteria” for river-friendly municipal policies.

Canal Park's fountain & rain garden
The new Washington Canal Park, just a few blocks east of the Washington Channel watershed, recycles stormwater not just for its site but also for three neighboring developments.

The impetus for these changes came from the 2011 renewal of DC’s “MS4 permit,” the EPA permit for the storm drains that drain the urbanized part of the Washington Channel watershed (and 2/3 of the District), and is managed by the District Department of Environment (DDOE). As part of this process, DC has adopted a completely new set of stormwater regulations with three key innovations:

  • a DDOE impervious surface charge to generate revenue for municipal green infrastructure, encourage existing buildings to reduce impervious cover, and reward “RiverSmart” properties (this is separate from DC Water’s impervious surface charge)
  • a retention standard that requires new buildings to retain 1.2″ of rainfall on site (~90% of all rain events), and renovations to retain 0.8″ on site
  • a credit trading scheme, the first in the country, giving the retention standard flexibility for dense downtown developments, rewarding efforts that go beyond, and generating funds for comparatively inexpensive GI improvements in the neighborhoods like Canal Park. By taxing bad things, like water pollution, you create an economic incentive to create good things, like neighborhood parks. (In DC, this creates a tidy way to “tax” federal offices through utility fees, and then build neighborhood parks.)

Although DDOE expects only 1% of the city to annually be affected by the retention mandate, that’s still 10X the area currently affected each year by voluntary green infrastructure efforts.

While this change in stormwater regulations is currently only tied to the separated storm drain permit managed by DDOE, DC Water hopes that these efforts will be able to have an appreciable impact on its troublesome combined sewer system. If so, DC Water may be able to renegotiate an existing EPA mandate requiring billions of dollars in new “deep tunnel” pipes (see pg. 7 of this Brookings report).

These just-implemented policy changes are already shaping up to have a positive impact on the Washington Channel watershed, where much of the urban fabric will change in coming years.

  • The Southwest EcoDistrict, a plan currently under development (primarily by the federal National Capital Planning Commission, with ZGF Architects) for the redevelopment of several blocks of mostly federal offices centered around 10th & D Streets SW, plans a truly cutting-edge water management scheme. The overarching goal is to reduce water use by 70% even while increasing the number of people on the site. Pages 11-29 of the May 2013 PowerPoint featured on their website goes into great detail about the strategies that the EcoDistrict can employ towards that goal: treating both greywater and air conditioning condensate water for potable use, storing a 1.7″ rain event in a truly vast cistern hidden underneath an existing bridge, and (by going beyond the 1.2″ mandate) receiving stormwater credits from other developments.
  • Over half of the Washington Channel’s urban frontage (over six blocks) is included within plans for the Wharf, a proposal to completely transform the Channel’s shoreline. The development embraces the Channel with a new riverwalk and several public piers that will bring the public down to the Channel’s water — very different than today’s gated-marina frontage. Complying with DC’s 1.2″ retention standard earns the Wharf the maximum number of LEED-ND points possible under the stormwater management credit, helping it achieve its LEED-ND Gold rating. Among the innovative strategies planned: using stormwater as process water within an on-site combined heat & power (cogeneration) facility that improves both energy efficiency and reliability.
  • Recent construction underneath the National Mall, part of which is within the Tidal Basin watershed, not only rebuilt the severely compacted turf but also included 500,000 gallons of rainwater storage in two cisterns — probably the city’s largest such installation. The Park Service plans another two cisterns as part of further Mall turf renovation, to store water running off the Mall (no, compacted turf doesn’t really do a great job of absorbing rain) and its drives for future irrigation uses. These cisterns could be just the start: in 2011, NCPC studied a two-block-long cistern, the entire width of the Mall, to store 20,000,000 gallons — enough to handle a 100-year rain event, and hopefully prevent the Federal Triangle from flooding again.
  • Stormwater fees are also having an impact on a smaller scale. My own apartment building near the Washington Channel, built during the concrete-happy 1960s, has just embarked upon an aggressive program to replace paved surfaces — open roof, impermeable walkways and driveways — with green or permeable surfaces. This long-overdue plan was put into motion due to the new impervious surface charge.

In the future, big storms like tonight’s (but not quite so big) might actually improve the Washington Channel’s water quality, instead of harm it. Later: a look at the Washington Channel’s water chemistry, plus what that means for future evaluation of the channel. But tomorrow, I’ll look at how the physical form of the Channel shapes habitats along, and within it.

This semester, I’m taking a Natural Resources class through Virginia Tech about understanding local watersheds, wherein I’ll be researching and posting knowledge about the Washington Channel. You can explore the other watersheds that my classmates are investigating over at the class blog’s page. Other posts in this series can be found using the tag watershed.

The rain falls upon this plain, but then what?

Washington Monument in a different reflecting pool

As I mentioned in previous posts, the Washington Channel is quite unique in that the water contained within it has little to do with its drainage basin: instead, its water is essentially imported from downstream via the tidal cycle. As such, its water quality (unlike almost all other waterways) largely does not reflect the land and water context adjacent to it. In addition, the Channel benefits from being entirely within the District of Columbia: the federal government has long held title over the waters (Morris vs. United States), and used parkland to create and frame the Basin and Channel. As a result of that unique context, not only does parkland surround all of the Tidal Basin and most of the Washington Channel, but the surface waters are also under federal protection.

Tidal Basin & Washington Channel hydrological maps

The Tidal Basin and Washington Channel do receive surface and groundwater runoff from their immediate areas, which together add up to 1.412 square miles of the District. The Tidal Basin drains 0.423 sq. mi., of which 0.169 sq. mi. (almost 40%) is surface water. 43% of the watershed is parklands and grass areas, including parts of the National Mall, the monuments ringing the Basin, and even the small hill underneath the Washington Monument.

Tidal Basin & Washington Channel hydrological maps

The Washington Channel drains 0.989 sq. mi., of which 0.3 sq. mi. (25%) is surface water. As its north bank is heavily developed, 53% of its watershed includes urban development, and the remaining 22% is parkland.

DC’s largest water pollution problem is its combined sewer/stormwater system, or “CSO.” (I’ll write more on these systems in later posts; they’re super-important for understanding urban water quality but not entirely relevant to this post.) This system, which is responsible for dumping a toxic brew of sewage and rainwater directly into many local waterways, drains one-third of the city, including most areas built before World War 2. However, since the immediate environs of the Tidal Basin and Washington Channel were redeveloped in a somewhat recent era, they have separate sewer and stormwater systems. This map shows the large parts of the city which have combined sewers — many of which, incidentally, are named after the creeks that they replaced:

Instead, smaller, separated storm drain systems — nine along the Channel and three along the Basin, delineated by the faint lines running roughly perpendicular to the water on the map below — intercept rainwater that falls on Southwest Washington’s roofs and streets, and dumps that untreated water into either the Tidal Basin (light blue on this map) or the Washington Channel (tan on this map):

Tidal Basin & Washington Channel hydrological maps

As you can see by comparing the first and last maps, the inland boundaries of the two watersheds are defined by these artificial drainages rather than the natural contour lines seen in the first map. If you look in the vicinity of N and O Streets SW, for instance, you’ll see that there’s a valley roughly between Third Street and Half Street. Historic maps show this as what was James Creek, which drained pretty much due south to the Anacostia River, but instead these blocks now drain “uphill” to the Potomac to the west.

The storm drains dump unfiltered water, often contaminated with urban pollutants, directly into the Basin and Channel. This contributes substantially to the substantial water quality problems within these two water bodies, but plans are underway to substantially reduce the quantity of these flows in the near future.

Sources for this post, notably the maps and geographic analysis of watersheds, include the DC Department of Environment’s water quality standards documents, which I’ll report on in greater detail in an upcoming post.

This semester, I’m taking a Natural Resources class through Virginia Tech about understanding local watersheds, wherein I’ll be researching and posting knowledge about the Washington Channel. You can explore the other watersheds that my classmates are investigating over at the class blog’s page. Other posts in this series can be found using the tag watershed.

Going with the flow: how Washington Channel’s mechanics impact its relative water quality

This semester, I’m taking a Natural Resources class through Virginia Tech about understanding local watersheds, wherein I’ll be researching and posting knowledge about the Washington Channel. You can explore the other watersheds that my classmates are investigating over at the class blog’s page.

In this installment, I’ll take a closer look at how the channel functions today, and what that means for its water quality. Other posts can be found using the tag watershed.

Last week, I examined how the silty Potomac started to clog the harbors around Washington, and mentioned how that resulted in the 1896 construction of the Tidal Basin and the Washington Channel. Today, we’ll investigate in some more detail just how the basin and channel work.

The satellite photo currently shown on Bing Maps appears to have been taken at low tide, when the Potomac River flows more or less as it always has, carrying fresh water east to the Chesapeake Bay and Atlantic Ocean:

Washington Channel: low tide

Note the high sediment levels in the Potomac, as indicated by its brownish color — it appears to carry more sediment than the Anacostia. I’ve highlighted the rivers’ silty water flows with greenish arrows.

At high tide, the picture looks very different, as the silty rivers collide with waves of clearer, darker ocean water racing upriver:

Washington Channel: high tide

The Tidal Basin-Washington Channel system uses the tidal surge to activate a pair of one-way gates. Imagine the Tidal Basin as being bound by two sets of doors that both only open inwards. The first set, the Potomac inlet gate, is at the Basin’s southern end: facing the flow of tidal water but perpendicular to the river’s flow. When the tide rises, the pressure of water flowing upstream pushes open the inlet gate, filling the relatively low basin with 250 million gallons of water:

Washington Channel & Tidal Basin at high tide

When low tide occurs, water recedes away from the Tidal Basin at the Potomac gate. The now-higher water in the basin tries to escape back out to the Potomac, but because those gates only open inwards, the water instead pushes the gates shut. (Water only pushes, not pulls.)

Meanwhile, at the Tidal Basin’s eastern end, an outlet gate leads to the Washington Channel. There, the gates open from the Basin to the Channel: they’re pushed open when the tide falls away from the Basin, spilling those 250 million gallons into the Channel, and they’re pushed shut when the tide rises.

Since the Channel is scoured during both the high and low tides, and is fed by the clearer tides and not by the muddy Potomac, sedimentation is no longer a problem and the channel retains navigable depth without the need for dredging. And since the Tidal Basin is fed by the tides — it’s always “high tide” in the Channel — the water within Washington Channel more closely resembles that of the Chesapeake Bay than the Potomac River next door. Thus its water is relatively clean, which is curious for a water body within the District of Columbia.

As a habitat, the Channel more closely resembles the brackish downstream Potomac than any of the neighboring freshwater rivers and streams. Fishermen know this, and set up along its banks to catch fish that have been swept upstream by the tide:

Washington Channel & Tidal Basin at high tide

In further installments, I’ll take a closer look at the shorelines, adjacent land use context, drainage, and water quality measures within the Channel.

Mud becomes concrete: Washington Channel’s history, told through maps

This semester, I’m taking a Natural Resources class through Virginia Tech about understanding local watersheds, wherein I’ll be researching and posting knowledge about the Washington Channel. You can explore the other watersheds that my classmates are investigating over at the class blog’s page.

In this installment, I’ll take a closer look at how the channel came to be a (sort of) discrete watercourse, to provide some context for later posts about today’s land and water quality. Other posts can be found using the tag watershed.

From Montreal to Providence to Trenton to Richmond, many of the East Coast’s great cities arose astride the “fall line,” an imaginary line along which its many rivers tumble from shallow rapids in the hills to slow, wide, sometimes brackish coastal estuaries. In an ocean-going era, such a location ensured easy access for oceangoing commercial boats, fresh river water, produce from farms upriver and fisheries downriver, and later to water power from the rapids or waterfalls alongside — all without the considerable downside of a coastal location’s vulnerability to frequent Atlantic storms.

[Minneapolis, built astride the falls of the Mississippi, could be considered the most interior of the East Coast’s fall line cities.]

Washington, D.C. is among these fall line cities, and its constant attempts to reshape the Potomac River’s banks also show the vulnerabilities that fall line geology also brings. Above Washington, the Potomac speeds through a narrow gorge, tumbling over its majestic Great Falls and past the high bluffs of wealthy towns like McLean, Potomac, and Georgetown. At Washington, three flows of water conjoin: the slower and broader Potomac, Atlantic seawater that tides pull all the way up the Chesapeake Bay and the Potomac estuary (with tides rising to 3.5′), and several surface flows. The comparatively flat topography of the L’Enfant City results from it resting upon a “shelf” of sediment brought there by the Potomac over time. This 1861 bird’s-eye view map by John Bachmann (from the Boston Public Library collection) plays up the topography, dramatically showing how the character of the Potomac valley changes at Washington:

Bird's eye view of part of Maryland, Distr of Columbia and part of Virginia

Several surface flows join the Potomac at Washington, notably the Anacostia River, Rock Creek, and Four Mile Run, but also several streams that have since been buried like Tiber Creek and James Creek. (David Ramos has compiled an impressive map of these buried streams.) From the very beginning of the city in 1790, plans were made to tame these streams for human uses like shipping. A map from the 1790s, drawn by John Russell, shows how city fathers, Pierre L’Enfant among them, conceived a system of drainage improvements. These canals were straightened channels based upon the east-west Tiber Creek and the north-south James Creek, both arising roughly where Garfield Park is today at the foot of the Capitol. The map also shows the outlines of the deeper, more easily navigable channels within the mostly shallow Potomac:

Plan of the city of Washington[...]

This idealized 1852 view, published by E. Sachse, illustrates the canals in an improbable shade of blue:

Shortly after Washington was founded, the Potomac’s plentiful sediment became a problem for the growing city. Land clearance for forestry and farming upriver combined with increasing levels of urban pollution dumped into local surface waters, making the water noxiously polluted — particularly during low tide, when pollution festered in exposed tidal marshes. The insalubrious tidal marshes at the mouth of Tiber Creek, beginning at the foot of the White House, appear to have given rise to the widespread myth that “Washington was built on a swamp.” The marshes are visible in these digital reconstructions of the 1791 shoreline:

Then and now: Washington Channel

Original and present shorelines of Potomac Park

The sediment buildup also threatened the city’s access to maritime trade. Given the marshes along the Tiber, the new city’s only shoreline adjacent to a deepwater channel within the Potomac was along its southwest waterfront. Wharves sprang up along Maine Ave. SW, landing fish and ferries that went to Alexandria and points beyond. In this process, this shore gradually urbanized and gained a “coat of armor” as buildings crept up to the water’s edge, as shown in this 1883 drawing by A. Sachse:

Private property owners’ interventions to shape the shoreline would soon be dwarfed by Congressional plans, particularly as the sediment threatened the relatively deep channel fronting Southwest’s wharves. Engineers (notably Peter Conover Hains) from what would become the Army Corps saw an opportunity to tame the city’s shoreline, preventing severe floods like that of 1881 from reaching the city’s core. Meanwhile, planners saw the potential for new parks — simultaneously adding land to the capital of a fast-industrializing country, meeting a post-Civil War national zeal for commemorative monuments, and providing Washington with a vast expanse of parks at its doorstep (as the fin-de-siecle era’s vogue the City Beautiful demanded).

This 1888 map by E. Kurtz Johnson depicts an early “cloverleaf” plan by Hains for filling in much of the Tidal Basin area, leaving a series of small pools that would be used to flush a new Washington Channel downstream:

In 1901, the City Beautiful reached its apogee here in Washington with the McMillan Plan. Shortly thereafter, the canonical birds-eye view of Washington had shifted 270 degrees; instead of placing the Capitol dome front and center with the filthy Potomac River in the distance, now bird’s-eye views proudly showed off the carefully sculpted shoreline, with its large and scenic Tidal Basin, an urban shoreline for the Washington Channel, and probably many more trees in Potomac Park than existed at the time (1916, drawn by H. H. Green):

Many of these maps courtesy of the Historic Print & Map Company, via DC Vote’s archive of Washington, DC, Historical Maps; high-res PDF versions can be downloaded there. Others were drawn from a Washington Post Magazine feature by Scott W. Berg, featuring mapping work done by architect Don Hawkins and Dan Bailey/UMBC Imaging Research Center.

Updated 17 May 2015 to fix broken links. The USGS recently made turn-of-the-century maps of DC available (the 1:62,000 scale is best); most show the Channel’s “final” boundaries, but are useful for observing urban growth and other topographical features.

Washington Channel’s trees and shrubs: a tale of two monocultures

This semester, I’m taking a Natural Resources class through Virginia Tech about understanding local watersheds, wherein I’ll be researching and posting knowledge about the Washington Channel. You can explore the other watersheds that my classmates are investigating over at the class blog’s page.

In this installment, I’ll take a closer look at the woody plants found along the channel. Other posts can be found using the tag watershed.

By and large, the plant life along Washington Channel is a tale of two monocultures. Its filled-in banks long ago had their native species removed; instead, people have planted two species in abundance: ornamental cherries in East Potomac Park on its west bank, and willow oaks on the circa-1970 Waterfront Park on the east bank. The effect of having so many identical trees might be unnatural but can be enchanting, certainly in the early spring when the world-famous cherries bloom:

Cherry Blossom Trees

And also in the autumn when the willow oaks turn gold:

Waterfront Park

The large shade trees planted here often were chosen to tolerate the damp, mucky landfill soil; some were chosen for ornamental fall color, as well.

  • Willow oak [Quercus phellos], as mentioned above, was planted along walkways and streets throughout Southwest Waterfront. Some have grown to ~80′ tall.
  • Scarlet oak [Quercus coccinea] is also found along streets.
  • Sugar maple [Acer saccharum] was planted along streets and in landscapes, perhaps for fall color.
  • River birch [Betula nigra] grows in a few clusters in East Potomac Park [photo].
  • Baldcypress [Taxodium distichum], a deciduous conifer common in bayous, has recently been planted near the golf course [photo].
  • Black willow [Salix nigra] is one of the taller trees along the channel [photo].
  • Swamp cottonwood [Populus heterophylla] also thrives along the west bank [photo].
  • Honeylocust [Gleditsia triacanthos] is a common urban street tree, since it permits dappled sunlight below.
  • American sycamore is another sturdy tree common to streets and parks.
  • Zelkova [Zelkova serrata] is another common street tree.
  • Eastern white pine [Pinus strobus] appears to be one of a few evergreens planted in East Potomac Park [photo].

As an intentional urban landscape lined with grassy or paved open spaces, smaller ornamental trees are more plentiful along the Channel.

Several urban weeds are also common along the Channel, notably white mulberry [Morus alba] and tree of heaven [Ailanthus altissima] [photo].

Plans for redevelopment of the Channel’s east bank, roughly between 6th and 12th St., call for a greater variety of mostly North American shade trees to replace the willow oaks. These include Kentucky coffeetree [Gymnocladus dioicus], honeylocust, tulip tree [Liriodendron tulipifera], blackgum [Nyssa sylvatica], swamp white oak [Quercus bicolor], and Chinese elm [Ulmus parvifolia].