Part 2: Plotting the Recurrence Time against the Peak Discharge The line spacing in a log-log follows a logarithmic progression: the spacing from "1" to "2" is the same as from "2" to "4", which is the same as from "4" to "8", and so on. Another way to look at it is that the distance from "1" to "10" is the same as from "10" to "100", and so on. Logarithmic graph paper should be used to plot figures that generally increase at a constant rate rather than by a constant amount, such as a stock price. Suppose the price of a share changes from $2 to $20 in ten years, then from $20 to $200 in the following ten years. If we plot the price against time using regular graph paper, it looks as if the investment growth is getting faster and faster. Yet someone investing $100 over the first ten years would have been able to sell for $1000, and someone investing $100 over the second ten years would also have been able to sell for $1000. So it makes sense that the graph should reflect this constant rate of growth. If we plot this share price on a logarithmic scale, we get a straight line. Other things best plotted on a log scale are the inflation rate, wages, prices, populations, and anything whose growth would normally be proportional to its amount. Using the log-log graph paper plot the peak discharge on the y-axis and the recurrence time on the x-axis. Then using a ruler, draw the line of best fit through the points on your graph and extrapolate it to 100 years. What is the peak discharge of the event that has a recurrence interval of 100 years? What kind of problems do you see in this system to compute the recurrence of the discharge?