where Sslide = the the total horizontal extent of erosion projected to occur during a complex deep-seated landsliding event (feet); and
Sbluff = the total horizontal extent of erosion projected to occur during a simple shallow sloughing event (feet).
and where the distances determined through the application of the above formula are referenced to one of the following locations: • The 'Ocean Shores Boundary Line', which corresponds to the location of the 16 foot N.G.V.D. contour datum as surveyed in 1969; • The 'toe of the bluff', which is typically represented as a distinct change in foreshore slope; or • The landward-most active 'headscarp crest', which is typically represent as the crest of the bluff.
Sslide. Values for this term are based on direct measurements of the extent of bluff failure. Relationships between bluff height and the landward extent of failure were identified by Gless et al. (1998). DOGAMI (1998) also identify relationships between bluff height, composition, structure and the landward extent of bluff failure. Following from this work, the value for Sslide is equal to 4.0 Hbluff or that given by DOGAMI (1998), whichever is greater.
Sbluff. This term was considered above in the context of bluff hazard areas. Here Sbluff is calculated as 1.5 Hscarp, where Hscarp is the difference between the elevation of the scarp toe and the elevation of the scarp crest.
To calculate relative risk these two parameters were combined as follows: Extreme Relative Risk in Slide Hazard Areas = Sbluff High Relative Risk in Slide Hazard Areas = Sslide + Sbluff Moderate Relative Risk in Slide Hazard Areas = 2 Sslide