Missouri Valley times. [volume] (Missouri Valley, Iowa) 1874-1931, 1907-05-02

T. Drainage District No. /.
Report of the Rectification of
the Soldier River and the
Drainage of Swamp Lands,
Harrison County, Iowa.
The Soldier River heads in Ida and
Crawford counties, and has water
shed in the uplands of 455 square miles
or 29l2O0 acres. The water shed is about
three times as long as wide, and is sub
divided into numerous minor divisions.
each having a separate discharge thru
a ravine or stream into The Soldier
river The surface CT the drainage ba-
sin is irregular, with slopes toward the
natural water channels, varying from
five to fifty and even one hundred feet
to the mile. The slope of the Soldier
river is greatest at its head, decreasing
as it approaches Orson. where it enters
the valley of the Missouri river Inn
mediately above 0rson, the Soldier
river has fall of about three feet to
the mile, after it enters the Missouri
valley the fall drops to one foot and
even less per mile.
Following the general course of the
Soldier river from Orson, it is some 25
miles to the point OF discharge into the
Missouri river, southwest of Modale.
Following the neanderings of the river,
the distance is considerably greater.
The general shape of the water shed
of the Soldier valley and the condition
and slope of its surface is such as to
produce maXimum flood discharges of
about 200o cubic feet per second This
may be increased at rare intervals by
storms of unusual severity to 5000 cubic
feet per second.
The water shed is in general cultiva-
ton, only a small per cent of its acreage
being in pasture and wood land. The
soil is a loam with. clay subsoil ard is
easily washed away by heavy rains. By
the time the flood waters reach the
channel of the Soldier they are sur
charged with sediment.
The greater the velocity of the water
the greater the amount and heavier the
particles of sediment carried.
In the past the water shed of the
Soldier was in grass, the roots of which
held the soil together and prevented
erosion. The water reaching the fat
portions of the channel was compar-
atively free from sediment. Fires kept
the brush and timbers burnt off and
there were fewer distractions in the
channel The soil has been broken uI
and cultivated. rendering it easily
eroded by very rain. The timber has
grown up along the stream The fallen
trees and brush have lodged in the
stream, retarding the flow of the waite,
and causing the channel to fill up by
the deposit of the sediment.
To properly protect the fiat lands
along the Soldier river, it will be neces.
sary TO not only control the floods ol
the river with a fixed channel, but also
to control the deposit of sediment car
ried by the flood water.
I The velocities at which water flowing
in an earth channel will move particles
OF soil, is generally stated as follows:
0.5 feet per second moves fine clay.
I 10 feet per second moves fine sand.
20 feet per second moves small grave
30 feet per second moves pebbles
inch in size.
4.ofeet per second moves spalls anG
stones
| These mus. he the vclocties along
the bed of the stream. The mean vcloc.
tiles must be considerably greater thar
these, for the reason that the friction
along the bed and banks retard the fila
ments of water next to them and the,
in turn rctard the adjoining filaments
The action of the air affects the sur.
face in the same way The fastest
moving filaments are short distance
below the surface of the middle Of the
stream. To produce mean velocity
of one foot per second, a portion of tho
water will be flowing considerably
! faster than one foot second. To pro
duce safety cleansing current. the
velocity along the bed should be two
feet per second.
The cross-sectional area Of the Sold;e,
river channel is about 22S square feet
The fall per mile as it flows is approx
! imately Que foot per mile, producing g
velocity of about one and fourth.
feet per second.
The velocity of the slowest flaments
will be two feet per second and better
1t is also seen that smaller channel
will be required to carry given guam
tity of water.
Assuming bottom width of forty
five feet, and computing the velocity
and discharges as before. we obtain
V-4.2 feet and Q 1902 cubic feet