FLOOD01888

• County: Statewide
• Title: River Hydraulics
• Date: 10/15/1993
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

e

.

~

.

.-

,e

,.

.
.

e

EM 1110-2.1416
15 Oct 93

101l1lP.ll 13,3'.),

100llDO

1:'1.1110'8 IIIVIlIt

,

.
.

..'

...

."

.
,

..,

."

OCT ,,"OV
1"3

Pill;: .JAil
I

FEll itA" A....

"A..- _"". ''''1. Aug lIliI.
1"1

KlIoVIUI. 0.. lI'l'Aall

HIloV%Z COH'O%.~ aoo STAO_
HAVI2 CDK'OTIID aoo Fl.OV

Figure 5-16. Hydrogrephs lor the illinois River et Hsvens with flow-Menning's n re".
tlonshlp edJusted to reproduce the 1983 flood

(b) In this approach, time is the only variable, and
the mathematics of the simulation reduce generally to an
ordinary differential equation. This equation relates the
sought after time variation of the outflow 10 the given
time variation of the inflow and 10 the given response
characteristics of the reach, e.g. a storage versus flow
relationship. The hydrologic techniques typically solve
this differential equation numerically, i.e. algebraically,
through the use of fmite-sized time steps.

values for both prof11es can be found. The usual
assumptinn is that the shape of the stage and discharge
profiles cannot be given a priori for the reach as a
whole. It must be broken into a sufficient number of
distance steps so that the shape of depth and discharge
variation in each can be assumed 10 be a straight line.
For this reason, the hydraulic techniques generally
require a determination of depth and discharge at a
sequence of stations within the reach, even if the condi-
tinns are in fact sought at only one point.

(6) The hydraulic approaches explicitly recognize, in
addition to the physical principle of mass conservation, a
second physical principle, one or another form of conser-
vation of momentum. If, then, an assumption is made
regarding the shape that graphs of the variation of stage
and discharge along the reach would have, absolute

(a) As a result, a characteristic feature of hydraulic
approaches is the calculation of flow variables in the
interior of the study reach, even if they are not of special
interest. For example, to arrive at the outflow

5-21