The times dispatch. [volume] (Richmond, Va.) 1903-1914, 1912-07-28
Near OLD Bridge Road. after


M is the drainage area in square
miles and is plotted on the axis Of
absciccas.
For the purpose of comparing these
! run offs with minimum flood dis
! charges. according to empirical formulas
! by J. T. Tanning and L. c. Murphy,
I civil engineers. the two upper curves
present maximum flood discharges that
| may be expected in North Atlantic
States as determined by Messrs Finn
| ning and Murphy after consideration OF
much data on food discharges In
many diferen, Watersheds.
The Pinu.
Tho plan for the Improvement Of
! the Chickahomfny River contemplates.
| % The deepening and Strengthening
! OF the present stream channel from
shove Alice TO Providence Forge.
! working distance OF $50 miles.
/ '2) The deepening and STRENGTHENING
ci the principal tributary. Brook Run.
ior distance upstream from its mouth
( OF about "a miles.
/ go The excavating OF new channels
or cut-ons at two points where tho
present bed OF the river is particularly
oircuitous total distance Of one-half
mile.
/ ca The repair OF existing bridges OF
'"'i' 'tp'aceh'eht win new ana sub
S'ol4'l 't SUI lures as dredging opera
'0''s may MAKE necessary
The improvements herein proposed
are shown on the large map and pro-
hle accompanying this report
Size of Chnnnci.
Havtnr .soo-,,trad .
tho ouent,t. o- r.a,or ~ . 80,
from the district the necessary size OF
channel TO care for that run-on was
compute" from the formula ~
substituting for the value as deter
mined by the Chezy formula - c RS.
II which equations
\ 2 cross sectional area OF channel in
square feet
c = quantity OF water OF discharge in
cnn1c feet per second
~ mean velocity IN feet per second.
C n coehlcient determined by Kutter's'
formula using Il coeiclent OF rough
ness NJ OOPS.
r. hydraulic radius.
S. sine OF slope.
Inc proposed channel. except for tho
crt-ofis' VIII follow mo present stream.
ana lts bottom Will average about loi
ieet below tho general level or tho
swamp necessitatng an average cut
. ting OF about 5.5 feet. The bottom
width varies from seventeen TO thirty
: i'.t and the side slopes as ordinarily
lot by a dredge woula 10 ons-halfl
horizontal 10 ono vertical Brook Run
has a bottom width OF fourteen rect,
Cut-ons.
with a view 10 shortening the dis !
tence and therefore Increasing tho
slope and removing bends number OF
cut-ons have been considered Only
two have hcon adopted. Although the
question Of cost has been tho deciding
factor IN most OF the reflections therel
are other important Considerations in
volving topography ami ownerships in !
separate parcels OF land Tho two cut
ors adopted, one ISIS feet long. at Rox-
bury and the other 2.165 feel long az
Long Reach Bridge. viii togetheri
shorten tho river channel nearly one
iniIe.
Bridges.
Tho Virginia Law requires drainage
districts TO remove. replacc ar con-
s,rnct bridges as may be necessary onl
public highways and railroads.
The numerous highways leading from
Richmond across tho Chickahominy
RIVER. together with three important
railroad bridges. will entail a consid-
cradle expense. In most cases tho
present highway bridges are low.
wooden ffa4rs. and II has been planu-
cd 10 replace them with more durable
structures. The reinforced concretel
bridge known as Grapevine Bridge and
! the substantial structures carryingl
the Chesapeake and Ohio E.ailrond overI
the river at Hunslett and Roxburv an
pear from the construction plans 10 ba
50 deeply supported and piled that dis
nantlinC the dredce to permi; II fol
phss under and permanent protection
81 the small amount ot piling when
Miii nc above the new water table