When fisheries biologist Rick Golden arrived on the Ozark-St. Francis national forest, the Forest Service showed him a simple spreadsheet used to evaluate soil sediment and its effects on streams and fisheries. According to the spreadsheet, any increase in sediment of more than 115% (about double) exceeds a "threshold of concern" and is supposed to trigger "more specific evaluation of the project and stream system." On the other hand, any increase of less than 115% means that sediment is not an issue.

Two simple examples illustrate the spreadsheet's perverse results.

Each analysis assumes a 1,000-acre watershed. In the first case (figure one), the watershed is pristine, i.e., there has been no past logging or road building. According to the spreadsheet, the Forest Service would only be permitted to clearcut 18 acres before exceeding the 115% threshold of concern.

In the second case (figure two), the 1,000-acre watershed already has 30 miles of existing logging roads, but no past logging. According to the spreadsheet, the Forest Service could clearcut all 1,000 acres of the watershed without exceeding the threshold of concern.

Of course, it is crazy that clearcutting every single acre of an already heavily roaded watershed would do less damage to streams than would clearcutting only 1.8% of an untouched valley. Yet that's precisely the result given by the Forest Service's sediment spreadsheet.

If you'd like to tinker with the spreadsheet by inserting your own numbers, here it is in Excel format.