United States. Inland Waterways Commission.

Preliminary report of the Inland Waterways Commission. Message from the President transmitting a preliminary report online

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Androscoggin, Penobscot, Merrimac, and Connecticut rivers. On
these streams navigation is largely limited to the tidal estuaries.
The basins are well forested and the natural permeability of the soils
is increased by the good humus wliich rapidly accumulates where
granulation, even of the heavy soils, seems to be a natural condition
when covered by the deep forest humus; the humidity is high and
the evaporation factor low. An extensive system of lakes, wliich
act as natural reservoirs, is instrumental in furnisliing an equable
stream flow from a moderate but evenly distributed precipitation,
which in winter occurs largely as snowfalls, and which passes off as
spring freshets after warm rains. Natural storage is also favored
by the deep glacial drift, the granitic soils, and the spongy moss and
deep humus. Sod naturally sets in ditches, on stream banks, and in
waste places, and forms nearly as perfect a protection against erosion
as the forest cover. Erosion is slight and the silt burden of the
streams is insignificant.

Nine of the principal rivers of the northeastern Atlantic coast
have total navigable water of 329 miles, or an average of 36 miles
for each stream.

The Kennebec may be taken as a type of the streams of tliis group.
It is navigable to Augusta, Me., the head of tide water; the tidal
stream, which is free from all silt bars, is open to boats with 10
feet of draft. Its sources are in the rolling plateau lake region, which
is submountainous in part. The soils, of gneissic and granitic origin,
in many places covered with glacial drift, are permeable loams and
sands on the lower portion of the basin; while equally loose soils
derived from sandstones, shales, slates, and conglomerates prevail
on the headwaters of the river. The headwaters are heavily forested
with spruce, while the lower portion of the river basin is less heavily
wooded with pine and hardwoods. A rainfall of 30 to 40 inches is
evenly distributed through the year, but the winter precipitation is
largely snow, which is released by April and May melting, the snow
remaining beneath the protection of the forest from one day to
several weeks longer than in the open. The forests have fine humus
conditions which afford liigh absorptive capacity and large water
storage. This is also supplemented by an ample lake surface which
has a decided equalizing influence on run-off. Dams at the lake



516 EEPORT OF THE INLAND WATERWAYS COMMISSION

outlets increase natural storage, releasing the water imtil September,
so that the flow of the river is fairly equable except during the spring
thaws. The amount of the summer run-off is further mamtained by
the low surface evaporation, 30 inches from a free water surface,
compared with 39 at Boston, and much higher rates farther south
and in the drier climate of the southwest. The numerous lakes,
the equable rainfall, the heavy forest cover, and the deep humus, all
combine to make this one of the most ideal of eastern streams.

The navigable portions of the streams of eastern New England
are largely the tidal estuaries, and are not subject to the alternation
of violent flood and low water which characterizes streams dependent
on rainfall for their depth of channel. The upper reaches, however,
are important in log transportation, since the time of the spring flood
is the season to which tliis is usuall}' restricted, while many streams
are very valuable for power or as sources of domestic water supply.

The silt burden of these rivers is small, and is largely limited to
material corraded from banks, and to the natural deepening of the
channels in the rapid portions of the streams. In the discussion of
Portland Harbor in the report of the Chief of Engineers the state-
ment is made (Report 1906, part 1, p. 33), that "no silt-bearing
streams empty into Portland Harbor, and the improved depth ob-
tained will be practically permanent." While many streams of New
England carry silt, the burden, considering the extent of the spring
floods, is small compared with that of southern and southwestern
streams.

The Penobscot, Androscoggin, and Merrimac rivers may be classed
with the Kennebec as having heavy-forested watersheds, with excel-
lent humus conditions, in addition to generally permeable soils and
an ample lake area. Surface erosion is slight and the silt burden low.
The stream channels are generally free from rapidly forming or shift-
ing silt bars. High spring freshets are followed by well-maintained
midsummer flow.

The headwaters of the Connecticut River lie in a much more moun-
tainous region, demanding therefore more extensive protection. Its
flow is not so steady as that of the Maine streams. Flood waters
gather more quickly and the dry season flow is lower. Erosion, on
account of the steep topography and the large farming area, is more
active, silt bars having formed in the tidal channel.

Large areas in the White Mountains, where this river has its source,
have been stripped of their forests, and subsequently burned. The
deep humus and duff, which in many places beneath the spruce
formed practically the only soil, has been destroyed. In the absence
of the natural absorbent cover, storm waters pass quickly and un-
checked into the river.

The Hudson River is similar in general characteristics to the New
England streams, but its chief tributary, the Mohawk, drains a thor-
ouglily cleared agricultural valley, and during freshets bears a heavy
silt burden. That portion of the river above Troy which comes from
the Adirondacks nearly duplicates in general character the streams of
Maine. The headwaters are in a region of low mountains with numer-
ous lakes, while the heavy spruce and hardwood forests serve to form
a deep, retentive humus which largely prevents erosion, as well as
promotes absorption and lessens soil evaporation. While the Hudson
is navigable only to the limit of the tidal estuary, the maintenance of



SPECIAL KELATIONS OF FORESTS TO RIVERS 517

the midsummer flow is of value in enabling larger boats to ascend at
low tide. It is subject to spring freshets from the melting of the
accumulated winter snow, followed by low water during the dry sum-
mers. The spring precipitation is usually low ; and wmle that of the
summer months is the highest for the year, the liigh evaporation
factor reduces the stream flow during the autumn. Rafter has
pointed out the influence of deforestation in increasing the irregu-
larity of the flow of streams in New York. During sixty years of
observation the minimum flow of the Schuylkill has diminished. In
1815 this flow was estunated at 500,000,000 gallons a dav; in 1825 at
440,000,000; m 1867 at 400,000,000; m 1874 at 245,000,000; since
then no measurements have been made. The commission of engi-
neers claimed in their report in 1875 that this was due to deforesta-
tion, there having been no change in the rainfall.

The silt burden of the Hudson, which has increased with the exten-
sion of the cleared area, amounts to 240,000 tons a year, a larger
amount than is borne by the rivers of New England, mth their better
forested watersheds, but smaller than that carried by the large
rivers of the southern Appalachians.

The streams of the Great Lake region, wliich include the head-
waters of the Mississippi River, with the St. Croix, Wisconsin, Chip-
pewa, and most other rivers of Wisconsin, Mnnesota, and northern
Micliigan, are similar to those of New England in lake feeding, the
topograpliic and forested concUtions of their basins, and the extent
of forest influences on their flow. These streams, however, have no
tidal estuary as have those of the northeast coast.

The soils of their basins are prevaihngly loose and possess a high
storage capacity. They are locally, however, deficient in cohesion,
and where this is the case, the banks of even small streams corrade
during the spring freshets. This produces sand bars, especially in
some of the streams of jMichigan, such as the Grand and Muskegon
rivers. Erosion, however, on the whole is so slight that the Missis-
sippi River above MinneapoHs, with a basin of 19,585 square miles,
has a yearh^ silt discharge of only 117,000 tons, compared with
10,000,000 tons from the Tennessee River, with only twice the area
of tliis portion of the Mississippi. The farming area will undoubtedly
be much extended in the region of these streams and as tliis takes
place it will be accompanied, unless the banks are carefully guarded,
by additional corrasion from the banks of smaller streams.

So far as known, sHght change has taken place in the flow of most
of these streams, but with the further decrease of the forest area the
spring floods will increase in size and the dry-season flow \W11 diminish.
This irregularity, however, will never be so marked as it would be
in the absence of the lakes and if the country were mountainous, the
soils close-textured, and the summer rains more concentrated. Addi-
tional lake storage for the equalization of stream flow is already being
utilized on the Mississippi, and on account of the favorable natural
conditions and the slight possibility of silting this admits of a great
extension. In addition to protecting banks of small streams, the
areas of lower agricultural value, haA^ng soils wliich erode, should be
maintained in forest. In the Northeast, the demarcation between
the absolute forest lands and those most suitable for farming is usu-
ally sharply drawn. For this reason further encrof^chment upon the
forest lands for farms will not be extensive, and if the forest condi-



518 • REPORT OF THE INLAND WATERWAYS COMMISSION

tions are not destroyed by injudicious lumbering, the present condi-
tions of stream flow can probably be maintained.

The most important problem connected with the control of New
England streams is the protection of the headwaters of the Con-
necticut. The extensive forest areas on the headwaters of tliis river
which have been burned should be reforested, and lumbered lands
should be protected from fire to allow early reestablishment of nor-
mal humus conditions. Future lumbering should be regulated so
that it will in no way jeopardize the humus and soil. On the Hud-
son River the preservation of the forests of the Adirondacks is
necessary to compensate for the extensively cleared valley of the
Mohawk, and to protect the lakes from silting up.

The removal of the forests has undoubtedly increased the ratio be-
tween maximum and minimum flow especially on the Hudson, Merri-
mac, and Connecticut rivers. This widened ratio can now be equal-
ized only by increased lake storage, but the existing condition can be
prevented from becoming worse by maintaining the present forest
cover.

RIVER SYSTEM OF THE MIDDLE ATLANTIC COAST

The most important streams of the Middle Atlantic Coast region
are the Potomac, Susquehanna, Delaware, Rappahannock, and James
rivers. Eight rivers of this group have total navigable water of
546.8 miles, or an average of 68 miles for each stream.

No one of these rivers is navigable above the fall line, which is at
or just above the tidal limit. The maintenance of a mid-summer and
autumn flow, regardless of freshets and silting, does not for this rea-
son assume the importance it does on streams which are extensively
navigated on other than tidal water. On several streams the supply
of water for canals is an important consideration. Their nearness to
large cities and their numerous falls and rapids make them valuable
as sources of power, while many of them, especially their mountain
tributaries, are used for obtaining municipal water supply. The two
unfavorable conditions which may be regulated by forest cover are
spring and winter freshets, and the silt burden which is deposited
largely through these freshets in the slack water of the tidal channel.

These streams rise in the Allegheny Mountains, where their head-
waters drain narrow agricultural valleys inclosed by forested but
thin-soiled shale and sandstone ridges. The lower portions of their
basins are largely cleared, and have rather heavy soils and frequently

f)oor humus conditions, both in the forests and in the agricultural
ands. The forest humus, derived chiefly from oak, chestnut, and
pine, is naturally scant except at lugh altitudes and has been further
reduced over large areas. Burning, exposing the soil to insolation,
and the compacting efi'ects of heav;^ rains have resulted in erosion.
Stream flow is maintained by a rainfall of from 40 to 50 inches, a
feature of which is a heavy, irregular midsummer precipitation, com-
pared with 30 to 40 inches of precipitation on the basins farther
north. The considerable winter snowfall is usually removed by warm
spring rains, causing floods, which corrade the banks of streams, and
also erode the agricultural lands. In addition there are frequent
summer and autumn floods, all accompanied by a large silt burden.
The floods produce damage to the canals and to riparian property,
while the silt is deposited in the estuary channels, where constant



SPECIAL RELATIONS OF FOEESTS TO RIVERS 519

dredging is required to maintain depth. The silt which is annually
discharged by the Susquehanna River at Danville, where the river
has a basin of 9,530 square miles, amounts to 240,150 tons. The dis-
charge of sediment by the Susquehanna had become so excessive by
1871 that it was found necessary that year to abandon the Brewerton
chamiel to Baltimore in Chesapeake Bay, since this channel was con-
tinually obstructed by the sediment deposited in the eddy made by
the currents of the Patapsco and Susquehanna rivers. The turbidity
of the Potomac and James rivers is liigher than that of the Susque-
hanna. On the James River it has been estimated* that in a flood
with a 10-foot crest from 275,000 to 300,000 cubic yards of solid
matter are moved during twenty-four hours.

These streams lack the natural reservoir system of lakes which
characterizes the streams of New England and many of the streams
of Wisconsin, Mchigan, and IVIinnesota. They also lack the sandy
or glacial soils of the northern river basins, wliich possess ample
water storage capacity. Moreover, the thinner humus of the oak
and chestnut forests offers only a meager water storage compared
mth that of the thick spruce duff and the moss of the more northern
streams. These conditions of soil and climate which are so unfavor-
able for equable stream flow attain their maximum for these rivers
on the lower reaches of the most southern streams, the Potomac and
James. Here the rainfall is heaviest and most irregular, the pro-
tective humus is thinnest, and the heavy clay soils of the Piedmont
Plateau, naturally deficient in granulation and absorptive capacity,
replace the more permeable, but shallow, sands and loams which
form the soils on the upper portions of their basins. On the upper
portions of the basins the conditions are more nearly like those which
determine the clearness of New England streams.

It is most desirable on these streams to reduce the number and
the height of the floods, since the turbidity and silt burden increase at
an accelerated rate as the floods become greater.

In basins of such character, temporary storage by other than arti-
ficial means, tending to prolong or distribute a flood crest, can be
secured only in the forest soil, and since storage in a forest soil,
except in sands, takes place very largely through the medium of
humus, it is necessary to maintain the humus at its maximum
depth. The humus in the valleys of these streams has been largely
reduced by frequent fires. By preventing fires, as well as by a more
judicious method of cutting when clean cutting is practiced, a humus
can be secured \vdth a high absorbent capacity over the greater part
of the forest area, which amounts to more than one-third of the
entire area of the basins.

Moreover, there are extensive areas of farming land situated on
steep slopes wliich will not hold a permanent grazing sod. The soil
is eroding badly, and consequently it has a low absorptive and storage
capacity. Its preservation seemingly can be effected only by re-
foresting. Reforesting, therefore, seems advisable, since not only
does the unchecked run-off from the naked slopes contribute to the
height of flood crests, but the earth washed from them largely aug-
ments that scoured by floods from the banks of streams.

oReport Chief of Engineers, U. S. Army, for 1885, pt. 2, p. 947.



520 EEPOET OF THE INLAND WATERWAYS COMMISSION

The construction of storage reservoirs at stream heads will lessen
corrosion by the high floods, but unless slopes are properly protected
by forest erosion from steep cleared land will continue, not only adding
its quota of silt to the stream channel, but threatening to reduce the
capacity and efficiency of the storage reservoirs as well.

RIVER SYSTEM OF THE SOUTHERN APPALACHIANS

This group includes a very large number of rivers, many of them
large and at present extensively navigated. Their navigable stretches,
however, can be greatly extended by furnisliing a more uniform flow,
and their usefulness can be largely increased by securing additional
channel depth either by artificial storage or by canalization. The
flow of these rivers is characterized by high floods at irregular inter-
vals, though usually in the spring, bearing enormous quantities of
sand and silt, followed by long periods of low water.

Tills system embraces the greatest number and most important
navigable rivers of the United States.

On the South Atlantic drainage, the Roanoke, Neuse, Tar, Cape
Fear, Santee, Savannah, and Altamaha rivers are all important.

On the Gulf drainage, the Appalachicola and Mobile River systems
embrace many hundred miles of navigable waters and traverse the
coal fields of Alabama.

The Tennessee, Cumberland, and Kentucky River basins cover
the entire State of Tennessee, a portion of northern Alabama, and
central and western Kentucky. The Ohio River system embraces
about 1,450 miles of navigable water. The lower Mississippi is
largely an extension of these streams, and its flow is chiefly depend-
ent upon their stages.

These rivers have their sources in the Appalachian Mountains or
in the adjacent plateau regions. In the lower portion of the Missis-
sippi Valley there are a few streams subject to nearly the same
influences, such as the Pearl River of Louisiana, which can appro-
priately be included. Fifty-seven of the Appalachian streams have
9,241.5 miles of navigable water, or an average of 162 miles for each
river. Most of them are navigable many miles above the tidal
limit. For this reason the maintenance of a liigh flow during the
dry season is important, as is also the reduction in the height of
floods, which seriously interfere with navigation on the upper reaches.
Closely related in effects to the dry-season flow is the silting up of
channels, wliich reduces the depth of navigable water. The power
wliich can be developed from these rivers is in many instances as
important as their use for navigation, especially in those regions
which are remote from the coal mines.

The most typical streams rise at high elevations, 3,000 to 5,000 feet,
in the Appalachian Mountains, where they are fed by many swift
tributaries. Leaving the mountains they flow less rapidly tlirough
the hill country of the Piedmont Plateau or the rolling farm region
of the Mississippi Valley. There is an entire absence of lakes and
natural reservoirs. Except in the most rugged portion of the moun-
tains the soil mantle over the greater portion of this region is ex-
tremely deep — from 20 to 50 feet. The soils may be separated into
three classes: (1) Loams and sands which are fairly permeable and
have high storage capacity; (2) silts wliich are less permeable and



I



SPECIAL RELATIONS OF FORESTS TO RIVERS 521

have a lower storage capacity, and which, on account of their
friabiHty, are subject to the most destructive erosion; (3) compact
clays deficient in granulation with, extremely low absorbtive power
ana low storage capacity, which erode badly but seldom destruc-
tively. The lighter soils are the most extensively developed in the
mountains, and are the sources of the steadiest perennial springs.
The heavy clays are extensively distributed, and cover hundreds of
square miles on the Piedmont Plateau. The unfavorable effect of
the prevailing close-textured soils upon stream flow is further in-
creased by the climatic conditions. The snowfall is light, except
in the high mountains, while the annual precipitation of 45 to 60
and even 80 inches at some localities frequently falls in concentrated
showers. As much as 9 inches is recorded as falling in twenty-four
hours and 21 inches wdthin one month. Such torrential rains are
destructive to steep slopes which are not protected by either sod or
the forest.

The forest at present covers only about one-third of the area of the
different watersheds. While the proportion of cleared land is appar-
ently not excessive, the condition and situation of much of it tend to
jeopardize not only the value of the rivers but the permanency of the
land as well. In the mountains extensive areas of very steep land
have been cleared. Some of this has a soil unsuited for farming and
failure to retain a grass sod has caused deep erosion. Continuous
cultivation in com has also resulted in the destruction of the value
of much land by erosion. With the rapid increase in population in
the past two decades, these conditions have become far more general.

The cultivation of extensive areas of hill country below the moun-
tains, especially of the red clays in the extreme south, has ceased.
The rural population has moved to the factory towns, or the negro
labor has gone to cities. Many counties in the Southern Piedmont
region show a decrease in rural population during the past two decades,
while in many there is a decrease in the total population. The sur-
face of the farm land abandoned in this manner has quickly hardened
and lost its porousness. Only a small amount of the heavy rains is
absorbed by it. Failing to absorb its due proportion of water, it has
added to the floods, while the springs formerly fed from the water
stored in the soil have failed. The land itself has eroded in deep
gullies.

Such unfavorable conditions are not limited to the farming soils.
The beneficial effects of the forest lands have likewise been reduced.
In the mountains, where the humus should be thick and have a high
absorptive and storage capacity and be efficient in maintaining soil
granulation, it has been destroj^ed by injudicious lumbering and by
forest fires. Below the mountains the humus, both in forest and in
farming soil, is generally deficient, the deficiency bein^ greatest
farthest south. This is partly due to the character of climate and
soil, which favor the rapid oxidation of humus, while fires and grazing
are additional causes for its depletion in the forest. The climate is
mild, the winters short, frequently open, and the ground uncovered
by snow; the summers are lon^, the humidity low, and the rainfall
irregular and concentrated. These conditions retard the formation
of humus and favor its rapid destruction.

31673— S. Doc. 325, 60-1 34



522 KEPORT OF THE INLAND WATERWAYS COMMISSION

The irregular, concentrated character of the precipitation associated
with these other favorable conditions frequently produces high fresh-
ets, not only in winter and early spring, when warm rains release the
stored waters of snow and ice in the mountains, but during the sum-
mer and occasionally autumn as well. The violence of these freshets,
in which the rise of water at the fall line of the rivers frequently
amounts to from 30 to 60 feet, temporarily checks navigation. On
the other hand, during periods of drought, which occasionally extend
to sixty and ninety da,js, the stream flow decreases until the depth of
water in the channels is too shallow for navigation. Rises of 50 or
more feet above low water are known to take place in the Cape Fear,
the Alabama, the Cumberland, and the Ohio, as well as in other streams.
While there has always been a wide limit between high and low water in
the southeastern streams, the ratio has undoubtedly widened as the
removal of the forest and the destruction of the humus in the remain-
ing forest have produced those conditions which concentrate in the
rivers the flow of the water of severe storms. The following table
shows the increase during a period of fifty years in the number of
floods on the Ohio River at Wlieeling.'* The flood stage is 20 feet.



Period.



Online LibraryUnited States. Inland Waterways CommissionPreliminary report of the Inland Waterways Commission. Message from the President transmitting a preliminary report → online text (page 59 of 83)