# Chapter 20 : RIVER ENGINEERING¶

## Example 20.1 pg : 888¶

In :
import math

#design  a guide bank required for a bridge in a river

#Given
Q = 50000.;         				#discharge
f = 1.1;           				#silt factor
bl = 130.;          				#bed level of river
hfl = 140.;         				#high flood level

# Calculations and Results
L = 4.75*(Q)**0.5;
L = L+212;          				#providing 20 percent more length
L_up = 5*L/4;       				#upstream length of guide bund
L_down = L/4;       				#downstream length of guide bund
r_up = 0.45*L;      				#radius of upstream curved head
print "upstream length of guide bund = %i m."%(L_up);
print "downstream length of guide bund = %i m."%(L_down);
print "upstream radius of curved head = %i m.;it can be carved at 145 degrees."%(r_up);
print "downstream radius of curved head = 287m.;it can be carved at 60 degrees.";

fb = 1.5;       				#free board
ltop = fb+hfl;  				#level of top of guide bund
print "level of top of guide bund = %.2f m."%(ltop);
print "adopt top level = 142 m.";
ltop = 142;
Hr = ltop-bl;
print "keep top width = 4 m. and side slope as 2:1.";
T = 0.06*(Q)**(1./3);         				#thickness of stone pitching
T = round(T*100)/100;
print "Thickness of stone pitching = %.2f m."%(T);
R = 0.47*(Q/f)**(1./3);      				#depth of scour
Rmax = 1.25*R;            				#maximum scour
rl = hfl-Rmax;            				#R.L at maximum anticipated cover
D = bl-rl;                				#depth of maximum scour
Lapron = 1.5*D;
R = round(R*100)/100;
Lapron = round(Lapron*100)/100;
print "depth of scour = %.2f m."%(R);
print "for straigtht reach of guide band:";
print "length of apron = %.2f m."%(Lapron);
Rmax = 1.5*R;
rl = hfl-Rmax;
D1 = bl-rl;
Lapron = 1.5*D1;
R = round(R*100)/100;
print "for curvilinear transition portion of guide band:";
print "length of apron = %.2f m."%(Lapron);
T1 = 1.9*T;
T1 = round(T1*10)/10;
print "thickness of apron = %.2f m."%(T1);
print "volume of stones:";
ss = 5**0.5*(141-130)*T;
as1 = 5**0.5*D*1.25*T;
ss = round(ss*100)/100;
as1 = round(as1*100)/100;
print "at shank:";
print "on slope = %.2f cubic metre/m."%(ss);
print "on apron with a slope 2:1  = %.2f cubic metre/m."%(as1);

va = 5**0.5*D1*1.25*T;
vs = ss;
vs = round(vs*100)/100;
va = round(va*100)/100;
print "U/S andD/S curved portion:";
print "on slope = %.2f cubic metre/m."%(vs);
print "on apron  = %.2f cubic metre/m."%(va);

ta = va/(1.5*D1);
ta = round(ta*10)/10;
print "thickness of launching apron = %.2f m."%(ta);

upstream length of guide bund = 1592 m.
downstream length of guide bund = 318 m.
upstream radius of curved head = 573 m.;it can be carved at 145 degrees.
downstream radius of curved head = 287m.;it can be carved at 60 degrees.
level of top of guide bund = 141.50 m.
adopt top level = 142 m.
keep top width = 4 m. and side slope as 2:1.
Thickness of stone pitching = 2.21 m.
depth of scour = 16.77 m.
for straigtht reach of guide band:
length of apron = 16.45 m.
for curvilinear transition portion of guide band:
length of apron = 22.73 m.
thickness of apron = 4.20 m.
volume of stones:
at shank:
on slope = 54.36 cubic metre/m.
on apron with a slope 2:1  = 67.74 cubic metre/m.
U/S andD/S curved portion:
on slope = 54.36 cubic metre/m.
on apron  = 93.61 cubic metre/m.
thickness of launching apron = 4.10 m.