Each erosion feature was delineated on photographic prints using a fine mapping pen, assigned a unique number, and the failure type (debris avalanche, soil slip, stream bank collapse or landing failure) was noted.
For the larger slope failure types (debris avalanche and landing failure) the 'scar' and the depositional material extending downslope from the source area (termed 'debris tail') were measured separately.
Often this increase is associated with road construction and subsequent road-related and landing failure (Mosley 1980; Pearce and Hodgkiss 1987; Fahey and Coker 1989, 1992; Beverley et al. 2001; Megahan et al. 1991, 2001).
Only four of the 12 landing failures contributed sediment to the stream network.
Conversely, landing failures generated <0.5% of the total sediment mass and delivered <0.5% to the stream sediment load.
Of the ~22 ha scar area, soil slips comprised ~11.6 ha, debris avalanches ~9.9 ha, stream bank failures ~0.3 ha, and landing failures ~0.2 ha (Table 4).
This storm initiated 931 new erosion features which included 441 debris avalanches, 451 soil slips, 27 stream bank failures and 12 landing failures.
This verified that for debris avalanche and landing failures their source area (scar) made up about one third of the total mapped eroded area (scar plus debris tail).
When Blue Origin first successfully landed their suborbital rocket in November, some were quick to compare Blue Origin's success to SpaceX's rocket landing failures at the time (although they successfully landed their Falcon 9 rocket later in December).
Of the 931 documented slope failures initiated during this storm, 91% of debris avalanches, 51% of soil slips, 33% of landing failures, and 100% of stream bank failures contributed sediment directly to a permanent watercourse.
Based on this approach, a sediment delivery ratio (SDR) of 0.5 for storm initiated debris avalanche and soil slips was adopted and applied also to landing failures on similarly steep slopes.
