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Klingle Valley from Top to Bottom: A Look at the Geology and Urban Hydrology of Cleveland Park’s Main Watershed Saturday, November 15, 2014, 9:30 AM – noon. The map on the last page shows the route and points of interest mentioned herein. The walk begins on 33rd Place in front of John Eaton School. Introduction Cleveland Park lies on the east slope of the Wisconsin Avenue Ridge, a terrace of the ancestral Potomac River and Washington’s highest landmass. A major part of the neighborhood is in large part defined by the watershed of Klingle Creek, whose two branches form prominent valleys that converge at Tregaron. The south branch originates near Woodley and 36th Streets and follows Woodley and Klingle Roads to Tregaron. The North Branch originates from the historical Cleveland Park Spring near Macomb Playground and occupies the ravine between Macomb and Newark Streets on its way to Tregaron and its confluence with the South Branch. The North Branch will be the focus of this walk. During the first century of Washington history, before Cleveland Park became established as a distinct neighborhood, the Klingle Creek watershed consisted mostly of large estates with a natural land cover that helped absorb heavy rains and allowed floods to spill harmlessly onto vacant floodplains. This changed with the advent of the Connecticut Avenue trolley line and, like many streams in the District, much of Klingle Creek was heavily altered by urbanization to make way for the new neighborhood. Sections of both branches were filled in and the stream put in underground pipes to create more real estate. Roads were built in the valleys, and much cutting and filling was done along the valley walls to create building sites. Most of the major changes to the hydrology occurred more than a century ago, and there are few, if any records of the subterranean infrastructure that now carries parts of the creek below the neighborhood; however, much useful information can be discerned by basic visual observation interpreted in the context of local geology. Today, a significant percentage of the watershed has been converted to various kinds of impervious surfaces (pavement, roofs, etc) at the expense of formerly open space. This means that a storm of any given size generates more surface runoff than it did a century ago—far more than the antiquated hydrology infrastructure was ever designed to handle—resulting in a variety of unwanted “surprises” for unsuspecting residents, such as erosion, foundation problems, road washouts, and flooded dwellings. This walk follows the North Branch of Klingle Creek, highlighting the natural history of the watershed as well as some of the challenges associated with this quintessentially urban stream. The route begins in the headwaters and follows the valley down Macomb Street to Tregaron (and, during the afternoon walk through Tregaron to its confluence with the South Branch at Klingle Road). Points of Interest 1. John Eaton School. The retaining wall facing 33rd Place on the east side of the school is a splendid geological exhibit. The wall contains nearly every major rock type found in the District, each quarried at a different location. Among others, you can see several types of metamorphic rocks, such as gneiss and schist, as well as the major igneous rocks that occur in the region. All of these rocks formed in a volcanic island arc known as the ‘Taconic Arc’. The arc originated at a plate boundary thousands of miles east of North America and, driven by plate tectonics, drifted westward until it collided with North America about 450 million years ago, thereby imparting a large piece of terrain that we now call the mid Atlantic. 2. Cleveland Park Congregational Church typifies the use of local building stone. The facing consists of ‘Rock Creek Granite’ and ‘Potomac Bluestone’, the two main types of local stone quarried from 1700-1938. The arches and keystones are made of Indiana limestone. The relatively level ‘bench’ in the hillside evident along the 3400 block of Lowell Street is an old river terrace that was made by the Potomac River or Rock Creek sometime after the Wisconsin Avenue Ridge was formed. It is one of several such terraces that descend, like a series of steps, from the Wisconsin Avenue Ridge to the modern floodplain of Rock Creek, each marking a stable, but short-lived position of the stream through the Ice Age. Patches of old, weathered gravel commonly underlie the benches and produce a hard, stony, infertile soil that challenges gardeners. 3. Cleveland Park Spring. A year-round spring emerges just below Macomb Playground. This is one of numerous hillside springs that emerge along the flanks of the Wisconsin Avenue Ridge and which acted as the primary water supply during the early years of the city. Several large springs near Glover Park, for example, served as the principal water supply for Georgetown until the mid 1850’s. Cleveland Park Spring is the source of the north branch of Klingle Creek, whose valley defines Macomb Street. It, along with springs in the vicinity of what is now Hearst Playground, and another spring on 36th Street near Woodley Road, were the water sources for early Cleveland Park residents. 4. Macomb Playground. Cleveland Park Spring currently emerges behind the houses immediately downhill of the playground. The spring has undoubtedly been modified over the last 2 centuries, first to make it more functional for water supply, and more recently to look more like a water garden. While the current location of the spring behind 3400 Newark St is probably close to the original location, it may not be exactly the same place. You may notice that the playground occupies a wide, bowl-shaped embayment in the hillside, the sort of place where one typically finds springs and seeps. It seems possible that the “spring” actually was a collection of several smaller springs and seeps where the playground now lies, before being disturbed when the playground was created (or possibly before that). Can we find any evidence for these features at the playground? 5. Rosedale and the Calvert Formation. This estate occupies an eastward extension of the Wisconsin Avenue Ridge and is characterized by extremely gravelly, infertile soil. The original vegetation here would have consisted of American chestnut, chestnut oak, and mountain laurel. Exposures of the beach deposits of the Calvert Formation can occasionally be seen in the bank along Newark Street, just above 35th Street. Look for sandy soil containing frosted white quartz pebbles, many of which exhibit the classic disc shapes of pebbles that rolled back and forth in the surf. The Calvert Formation contains fossils of single celled siliceous marine organisms, known as diatoms, which indicate that the part of the formation deposited near here dates from the Miocene and is about 16 to 17 million years old. Much of the soil surface along this section of Newark Street is littered with pebbles and cobbles washed down from the summit of the ridge. The gravelly sediment of the Calvert Formation is rather porous and is the likely source of the Cleveland Park Spring. 6. The 3200 block of Macomb Street. For the first 2 blocks below 34th Street, Klingle Creek is a free- flowing stream that occupies the bottom of its natural valley. The sidewalk along the east side of 34th Street affords a view downvalley. As you walk down these blocks of Macomb Street, notice how close many of the homes on the north side of the street are to the bottom of the ravine. This is because the side of the ravine was cut and filled to make way for the homes and street. Many homes originally had driveways that led to garages behind or underneath the house, nearly at stream level. It was not uncommon for these garages (and basements) to be inundated during major floods. Today, some of the former under-house garages have been converted to walk-out basements, which is a risky proposition. In contrast, the homes on the Newark Street side of the ravine stand far above the bottom because they were built on a naturally level stream terrace, whose flat, gravelly character is highly evident in the 3300 blocks of Newark Street and Highland Place. 7. Lost Valley. The creek abruptly disappears behind 3203 Macomb Street, and remains below ground until it reemerges below the entrance to Tregaron. In this section of Macomb Street, the bottom of the ravine was completely filled in and the stream is being carried through an ancient network of storm sewers. A tributary stream that originates near Highland Place also enters the main valley in this section, but the location of the original confluence is unclear because both streams are now carried in storm sewers. Little is known about the size or age of the pipes that convey the stream through this section, but they probably date from a century ago and are insufficient in size to contain the flow during a major flood. Topographic maps show the general outlines of the original valley bending southeast as it approaches the entrance to Tregaron, and the steep slope of the valley wall is visible directly behind west side of the apartment building at 3039 Macomb Street. At least the first 2 or 3 houses in the 3100 block are be built on fill directly over the deepest point in the lost valley. 8. Outfall. The stream reemerges from an outfall not far inside the entrance to Tregaron. The precipitous grade of the stream is readily evident looking downstream from this point—the total fall of the stream is more than 50 feet on its short (~1,100 feet) journey through Tregaron.

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