function [v,q] = vanq(w,d,n,s)
%[v,q] = vanq(w,d,n,s)
%This function determines the velocity (v) and discharge (q)
%at a point in a channel using the Manning equation
%for velocity given these independent variables for a rectangular
%channel with a single roughness (English Units):
%	w = width of channel (feet)
%	d = depth of channel (feet)
%	s = channel local slope in rise/run
%	n = mannings roughness coefficient in ft^1/6
%		see http://geology.asu.edu/~glg410/Labs/manning.html

%	Internal variables:
%	a = channel cross-sectional area
%	p = wetted perimeter (2w + d)
%	r = hydraulic radius (a/p)
%JRA, 11/29/1999

%write parameters
fprintf('Channel width is %.3f feet, depth is %.3f feet, slope is %.5f, and n is %.3f\n', w,d,s,n);

%calculate internal variables
a = w*d;
p = (2*d+w);
r = (a/p);
fprintf('Channel area is %.3f feet^2, wetted perimeter is %.3f feet, and the hydraulic radius is %.3f feet\n',a,p,r);

%calculate velocity and discharge;
v = ((1.49/n)*(r^(2/3))*(s^(1/2)));
q = v*a;
fprintf('Flow velocity is %.3f ft/sec, and discharge is %.3f cfs\n',v,q);