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both sides by prominent flat terraces 140 to 160 feet above the stream and 100 or 150 feet below the less prominent Berea terrace. The stream is not hampered by resistant rock, and its valley across the quadrangle is well graded. There are no falls and rapids in its course, and it has no gorge. The whole valley is evenly and broadly opened down to the level of the Berea terrace, and below that level a narrower inner valley has been cut. The rock walls of the valley descend with moderate gradient to the level of the Berea terrace, then more steeply to the level of the glacial silt terraces, and pass beneath them. The surface of the Berea terrace is much dissected by streams and descends upstream. That of the silt terraces is very level, with a gentle slope toward the center of the valley and a slope down the valley of about 7 feet to the mile. Its altitude is 800 to 820 feet at the south edge of the Cleveland quadrangle and 700 to 730 feet in the southern part of Cleveland. This terrace is divided into separate patches by the trenches which the river and its tributaries have cut into it. The river flows through it in a sinuous trench from 100 to 140 feet deep and from a quarter to half a mile wide. The swinging

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FIGURE 2-Section across the Cuyahoga Valley from Walling Corners to Macedonia. Modern channel is shown at east side of old valley; terraced surface on glacial valley filling at the west

of the river carries the trench from one side of the valley to the other. Where it is against one of the rock walls of the valley, as at Boston, Brecksville, and Southpark, a broad remnant of the terrace lies. between it and the other valley wall. (See fig. 2.) Where it is in a more central position remnants of the terrace may be seen on each side. At Southpark the river hugs the west wall, and the broad terrace on the east is cut squarely through by Tinkers Creek. At Brecksville the river flows against the east wall, and Chippewa Creek, coming in from the west, cuts across the terrace to reach the river. With its flat top and steep fronts this terrace forms a conspicuous feature all along the valley. The altitude of the terrace, 730 feet in the southern part of Cleveland, corresponds with that of Middle Ridge.

The valley of the Rocky River presents a strong contrast to that of the Cuyahoga. The upper part of its East Branch also follows an old valley, whose course across the Cleveland and Berea quadrangles is plainly shown on the geologic maps. In general appearance this part of the valley is like that of the Cuyahoga-broad and with high rock walls, though not so deep as the Cuyahoga Valley.

East of Strongsville the river forsakes this old valley, and thence downstream the valley has an entirely different character. Above Berea it is developed in a weak shale, is about a quarter of a mile wide, and is flat bottomed and bordered in places by nearly vertical walls of shale 10 to 30 feet high, decreasing in height northward. At Berea the stream flows in a narrow trench in sandstone and a fall and short gorge occur just north of the town, where the stream cuts through the sandstone into the shale below. From this point to the mouth of the river the valley is flat bottomed and steep walled, in a few places as much as a quarter of a mile wide, and has vertical walls of shale 100 feet or more in height. The West Branch has a similar fall and gorge at Olmsted Falls. Where the two branches come together at Olmsted, two prominent, isolated rock hills occur in the middle of the valley. They are quadrangular and bounded on all sides by precipitous shale bluffs. These are remnants of the shale promontory between the two branches of the river, which long ago came together below the hills, later cut across between them, forming the north hill, and later still came together as they now do.

At Kamms the stream crosses the old valley, which had been entirely filled with glacial drift, and here its present valley widens to three-quarters of a mile and its walls are of glacial drift and less steep than above. At the big bend at Rockport the valley reaches the east edge of the old filled valley, and the west wall of the present valley consists of drift and is in strong contrast with the shale cliff that forms the east wall.

The larger creeks of the quadrangles all have a fall over the Beres sandstone and a gorge below it. On many of those that flow into the Cuyahoga the falls are high and the gorge steep and long, as on Tinkers, Brandywine, and Chippewa Creeks. On those that flow to the lake-Euclid Creek and Doan Brook, for example-the gorge continues to the escarpment, beyond which the stream crosses the Erie Plain in a shallow valley.

A large part of the city of Cleveland is built on a nearly flat platform having a gentle northerly slope, on the surface of the Pleistocene deposits that fill the old Cuyahoga Valley. In this part of the city bedrock is far beneath the ground surface.

DRAINAGE

General character. The three quadrangles drain entirely into Lake Erie. The greater part of the drainage passes through northwardtrending valleys of medium size, which are rather uniformly spaced across the region, one for every 10 to 15 miles or about one to each quadrangle. The Cuyahoga River is the stream of this type for the Cleveland quadrangle and the Rocky River for the Berea quadrangle. The Black and Chagrin Rivers are the corresponding streams for

the quadrangles next west and east of the Cleveland district. The subsidiary drainage of the areas between the rivers flows into these rivers, except in that part nearest the lake, in which small streams flow directly into the lake. Euclid Creek and Doan Brook, both east of the Cuyahoga, are the largest of the minor tributaries to the lake. A notable tendency of the subsidiary drainage is to flow for considerable distances parallel to the shore of the lake instead of toward it. The low ridges that roughly parallel the lake shore-the lake ridges and the moraines-impose this course on the streams. The East Branch of Euclid Creek flows southwestward along the south face of the Euclid moraine. Butternut Ridge turns Big Creek out of its northerly course at North Linndale, sharply eastward to the Cuyahoga. A number of small brooks flow behind the lake ridges in the Berea quadrangle.

The streams of the plateau flow in all directions, but those that do not flow north become tributary to some stream that does flow north. Thus in the southern part of the Cleveland quadrangle Furnace Run flows southeast, but it reaches the Cuyahoga south of the limits of the quadrangle. The extreme upper part of the East Branch of the Rocky River flows southeast, in the reverse direction to a lower part of its own flow to the northwest. These various directions are controlled by the local surface slopes, which in turn are largely due to modification of the normal slopes by glacial deposits. Cuyahoga River and other streams.-The Cuyahoga River is about 100 miles long. It rises in the highlands of Geauga County within 15 miles of the lake shore and flows 60 miles southward and southwestward away from the lake. It reaches the old preglacial valley, in which it flows northward to the lake, at a place 30 miles southeast of Cleveland. Its course is separable into three parts-the long upper, southwesterly course, which is in a shallow and uneven channel through glacial topography, with no well-marked valley, and in which the fall is 600 feet, or about 9 feet to the mile; a short middle course, where it falls 220 feet in a gorge 11⁄2 miles long, cut back into the east wall of the old valley; and the lower, northward course in the old valley, the only portion within these quadrangles.

The Cuyahoga carries to the lake the entire drainage of the Cleveland quandrangle, except the extreme northeast and southwest corners, and also the Big Creek drainage of the eastern part of the Berea quadrangle. The stream is thoroughly graded, except for a few small rapids. It is very tortuous, its name, of Indian origin, meaning "crooked." Its actual length across the Cleveland quadrangle, following the channel, is more than 40 miles, or more than twice as great as the air-line distance along the valley. In this distance it drops 80 feet, so that the fall is less than 2 feet to the mile, which is much gentler than that of any other stream of the region.

The average discharge of the river at Independence is about 700 secondfeet, from a drainage basin containing about 900 square miles, which is about 0.8 second-foot to the square mile. The flow is much the largest in March and least in midwinter and midsummer.

The chief tributaries to the Cuyahoga are Tinkers, Brandywine,. and Mill Creeks from the east and Chippewa and Big Creeks and Furnace Run from the west. Tinkers Creek is the largest of these. It enters the quadrangle at the place where a moraine diverts it sharply westward from the old valley occupied by its upper part. In strong contrast to its broad upper valley, it occupies within the Cleveland quadrangle a narrow, steep-walled gorge, 100 feet deep, with a 30-foot fall over the Berea sandstone at the head of the gorge at Bedford. This part of its course is less than 7 miles long, and the drop is 310 feet, or 45 feet to the mile. Its upper course is longer and has a much gentler gradient of about 7 feet to the mile. Big Creek is about 14 miles long and drops 630 feet, an average grade of 45 feet to the mile. It is a shorter and smaller stream than Tinkers Creek and should normally have a steeper slope. Chippewa Creek is about 7 miles in length and has a drop of more than 500 feet within that distance, or more than 70 feet to the mile, with its falls over the Berea sandstone just below Brecksville. The fall of Brandywine Creek over the Berea sandstone at Brandywine, a straight plunge of 75 feet, is the highest fall within the quadrangles. Mill Creek has a similar profile.

The Rocky River is a much smaller stream than the Cuyahoga, though no measurements are known of its volume. The source of the East Branch is not more than 30 miles south of the lake, and, except the headward part, it flows directly toward the lake. With the East Branch it is about 35 miles long and has a gradient of about 18 feet to the mile. Across the Berea quadrangle the West Branch falls about 10 feet to the mile. This is two and one-half times the Cuyahoga gradient, and the discrepancy is due chiefly to the differences in the two valleys, which have already been described.

The Euclid quadrangle is drained by streams that flow directly into the lake, chiefly Euclid Creek, Doan Brook, Dugway Brook, and Ninemile Creek. These all rise well back from the escarpment, on the gentle shale slopes of the Appalachian Plateaus in Warrensville Township, and flow northward in very shallow, narrow valleys to the places where they fall over the Berea sandstone into narrow, rock-walled valleys about 100 feet deep that have been cut backward from the edge of the Appalachian Plateaus. From the escarpment at the edge of the plateau they flow northward in shallow trenches in the Erie Plain to the lake.

The Erie Plain is so narrow across most of the district that it has no drainage distinct from the plateau; a number of small streams

head on the escarpment and flow directly across it to the lake. West of the Rocky River, where the plain broadens, the entire drainage of the plain consists of such streams, of which Cahoon and Porter Creeks are the largest. In this district the headwater parts of such creeks are much deflected by the lake ridges that cross their courses, as shown on the topographic map. Their valleys are shallow except near the lake, where they notch the shore cliffs, some to depths of 30 to 50 feet. The larger streams all flow across the plain in sharply cut, generally narrow valleys from 50 to 100 feet deep.

Springs. The two great porous sandstones of the region, the Berea and Sharon, give rise to a host of copious springs along their lines of outcrop. Many streams head in the springs from the Sharon. Although there are springs of other origin also, these are so constant and abundant that they form a characteristic feature of the drainage.

BEDROCK SURFACE

In the Appalachian Plateaus the altitude, relief, and larger topographic features are due chiefly to the form of the bedrock surface, and only the minor drainage lines are completely filled by the drift. In the Erie Plain, however, the preglacial valleys are all filled about to the level of the interstream tracts, and it is only by boring that their positions and courses are determined. On the part of the plain within the Cleveland district the coating of drift on the preglacial interstream areas probably averages not more than 15 feet in thickness, but in northwestern Ohio these tracts as well as the preglacial valleys are covered with thick deposits of drift.

The most prominent parts of the Appalachian Plateaus within the Cleveland area have the resistant Sharon conglomerate as the cap rock. The Berea sandstone forms the immediate border of the Appalachian Plateaus east of the Cuyahoga River but runs into the Erie Plain near the west side of the Cleveland quadrangle. It stands somewhat above the area to the north of the plateau as far west as Berea but is buried under drift in the western half of the Berea quadrangle. This sandstone causes cascades on most of the streams that cross it.

The rock floor of the preglacial valleys is much lower than the beds of the present streams and in places much lower than the bed of Lake Erie. The present streams are controlled by the surface of the lake, but the preglacial drainage lines were connected with a trunk stream in the Erie Basin whose valley was cut to a level far below the bed of the present lake.

Borings in Cleveland and along the Cuyahoga Valley have shown the presence of a remarkably deep channel, with a rock floor in places near sea level. The preglacial valley is practically followed by the present river from Akron down as far as Willow, but from Willow to

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