Thermal Loading

Step Wise Guide

Riparian Management

· In the context of forest management, what parts of my watershed and stream network are most sensitive to changes in solar radiation loading?

One concern about timber harvest near streams, including thinning, is whether reduction in forest vegetation will lead to significant changes in thermal energy reaching the stream. The supply of thermal energy to a stream is driven by numerous factors including the lat-long position of the river, the time of year and time of day, the size (width) of the stream, stream orientation, topographic shading (ridges, valleys etc.), and vegetation shading. Thermal energy is an important component of stream temperature in addition to how it influences air temperature, but other important (but often hard to define) factors include flow volume (m3/s), groundwater conditions including local hyphoreic flow, near stream vegetation such as bushes, and substrate. When planning timber harvest, designing riparian buffers, or forest or stream restoration, it is helpful to have an estimate of how different channels have different thermal loading characteristics. NetMap contains a tool for estimating that.

Step 1: Go to NetMap's Riparian Management Module>Thermal Load Tool. This tool can take considerable time, and so a user might wish to select a set of channel segments, either a handfull of them or a tributary population of stream segments. An estimate of riparian vegetation is required, in terms of height, density, and width of the stream side forest (which in the case of unharvested forest, can be set to say 100m). The output includes thermal loading with the selected forest (or buffer) condition, bare earth loading (without any vegetation), and the difference between the two. The latter can be considered a type of sensivity analysis, indicating where, if vegetation were removed (or burned), channels might experience the largest change in thermal loading.