[Interior Watershed Assessment Procedure Guidebook Table of Contents]

Appendix 4.

How to produce a hypsometric curve and determine the H60 elevation.

In much of the British Columbia interior, snow typically covers the upper 60% of a watershed when streamflow levels begin to rise in the spring. The H60 is the elevation for which 60% of the watershed area is above.

To estimate the elevation of this snowline (H60), draw a hypsometric (area-elevation) curve for the watershed as shown in Figure 4-1. A hypsometric curve is constructed by calculating the area between contours (use 100 m) on a topographic map and plotting the cumulative area above a given elevation versus that elevation. If the difference between the highest and lowest elevation in the watershed is less than 300 m, use the entire watershed to estimate the equivalent clearcut area.

Figure 4-1. Sample hysometric curve.

In the level 1 procedure, only one H60 line needs to be produced for the entire watershed. Individual H60 lines do not have to be produced for each sub-basin identified unless a particular sub-basin will be the focus of a complete, individual WAP.

[Return to top of document]