"The Effects of the 1997 Floods on the Klamath National Forest (De La Fuente, 1998) provides an in depth analysis of the types and locations of landslides and road failures on the forest. The January 1997 storm caused catastrophic damage to the road system of the Klamath National Forest (KNF), with over $27 million dollars damage. Funding for repair of the roads and other forest infrastructure damaged by the storm is provided through the Emergency Relief for Federally Owned Roads (ERFO). Flood damage sites, known as ERFO sites, were predominantly road failures and 712 sites were funded for treatment. De La Fuente (1998) considered precipitation, flows, storm recurrence interval, elevation, geology, slope and previous management for links to flood damage. The geographic area of the study was from the Trinity Alps, in the headwaters of the South Fork Salmon River, north through the Marble Mountains and into the Indian Creek and Beaver Creek watersheds in the Siskiyou Mountains.

The storm recurrence interval varied from 14 to 37 years, which indicates that it was not a catastrophic event on the scale of the 1964 flood (100 year). De La Fuente (1998) found that the most severe damage to roads and streams did not necessarily coincide with the areas with the greatest recurrence interval. Over 446 miles of stream channels in the Klamath National Forest were altered by the January 1997 storm event, some sustaining complete scour and others only moderately rejuvenated. Many streams experienced major bedload movement, channel widening and shallowing and changes in bed composition, often an increase in fine sediment. Channel widening caused a loss of riparian vegetation that in turn allowed considerable warming in some streams. Shallower streams also are more subject to warming.

The most landslides occurred in the 4000-6000 foot elevation range, triggered by a rain-on-snow event. The greatest flood damage to roads occurred at the 2000-4000 foot elevation levels as debris torrents initiated at higher elevations took out road crossings at lower elevations. While the greatest number of landslides occurred on undisturbed sites (255), there were 243 landslides in recently burned areas, 215 in recently harvested areas (since 1977), 182 along roadbeds and 60 in old harvest sites. It is instructive to look at the number of slides per square mile with regard to undisturbed, burned, harvested and roaded areas. Roads had by far the highest failure rate per area of landscape with 7.34 landslides per square mile and burned and recently harvested units yielding similar landslide rates of 1.58 and 1.61, respectively.

Road failures at higher elevations some times were the initial source of the debris torrent. The failure of multiple crossings in one tributary can have catastrophic consequences as the fill material at each crossing is added to the debris torrent. Impacts to stream channels often continued into reaches at lower elevations. Many landslides and road failures occurred on old or active landslides or landslide deposits and in the inner gorge area adjacent to streams (De La Fuente, 1998).
De La Fuente (1998) used aerial photos and ground surveys to map landslides and road failures that occurred as a result of the January 1997 storm. Landslide and road failure raw data was not available for use in this study; therefore, estimates of the number of these features by watershed were estimated by counting points on maps."