20 BULLETIN 1430, U. S. DEPARTMENT OF AGRICULTURE 
24 hours. The discharge of sediment by the Susquehanna had 
become so excessive by 1871 that it was found necessary that year 
to abandon the Brewerton Channel to Baltimore in Chesapeake 
Bay, since this channel was continually obstructed by the sedi- 
ment deposited in the eddy made by the currents of the Patapsco 
and the Susquehanna Rivers. The average turbidity of the Sus- 
quehanna is 21 parts per million, and that of the Potomac and James 
Rivers is higher. 
A most notable power development on the Susquehanna River is 
the projected plant at Conowingo, where it is estimated the initial 
generation will render available 300,000 horsepower, and possible 
additions will produce 500,000 horsepower, thus placing this river 
in the class with the Tennessee as one of the great power streams 
of the Eastern States. 
These streams lack the natural reservoir system of lakes which 
characterize the streams of New England and many of the streams 
of Wisconsin, Michigan, and Minnesota. They also lack the sandy 
or glacial soils of the northern river basins, which possess ample 
water-storage capacity. Moreover, the thinner humus of the oak 
and chestnut forests of the Middle Atlantic coast region offers only 
a meager water storage compared with that of the thick spruce 
duff and the moss of the more northern streams. 
These conditions of soil and climate, which are so unfavorable 
for equable stream flow, attain their maximum on the lower reaches 
of the most southern streams, the Potomac and James. Here the 
rainfall is heaviest and most irregular, the protective humus is 
thinnest, and the heavy clay soils of the Piedmont Plateau, natur- 
ally deficient in granulation and absorptive capacity, replace the 
more permeable though shallow sands and loams of the upper por- 
tions of their basins, where the conditions are more nearly like those 
determining the clearness of New England streams. 
RIVER SYSTEM OF THE SOUTHERN APPALACHIANS 
The southern Appalachian group includes a very large number of 
rivers the flow of which is characterized by high floods at irregular 
intervals, usually highest in the spring, followed by long intervening- 
periods of low water. 
This river system embraces the greatest number of navigable rivers 
in the United States and has the greatest mileage of navigable waters, 
although at the present the rivers are very little used in comparison 
with the actual possibilities. The total power resources, minimum 
flow, are placed by the Geological Survey at 3,340,000 horsepower. 
On the southern Atlantic drainage the Roanoke, the Neuse, the 
Cape Fear, the Peedee, the Santee. the Savannah, and the Altamaha 
Rivers are all important streams. With these can be included the 
White River and other streams of the Ozark region. On the Gulf 
drainage the Apalachicola, the Black Warrior, and the Mobile River 
systems embrace many hundred miles of navigable waters and trav- 
erse the coal fields of Alabama. The Tennessee, the Cumberland, 
and the Kentucky River basins cover the entire State of Tennessee 
and portions of other States. (PI. 14, figs. 1 and 2.) The rivers 
have their sources in the southern Appalachian Mountains or in the 
adjacent plateau regions. In the lower portion of the Mississippi 
