Steep Slopes Hazard Map North Pender

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Steep Slopes Hazard Map
North Pender Island
00.511.520.25
Kilometers
Moderate Hazard (22.5 - 45 degrees)
High Hazard ( > 45 degrees)
Property Boundaries
Low Hazard (15 - 22.5 degrees)
Supporting Data and Limitations 
 
 
This  North  Pender  Island  Steep  Slopes  Hazard  Map  has  been  created  using  a  slope  gradient  generated  from  a  digital  elevation  model 
(DEM). A DEM is a digital representation of ground surface topography, or topographic relief, built using remote sensing techniques and 
aerial  photography.  There  are  a  number  of  limitations  in  utilizing  aerial  photographs  to  develop  Digital  Elevation  Models  (DEM),  which 
should be noted when considering the spatial resolution of the mapped hazard areas. The quality of the DEM may vary according to many 
conditions:  terrain  roughness,  sampling  density,  grid  resolution  (or  pixel  size),  interpolation  algorithm,  vertical  resolution  and  terrain 
analysis algorithm. The quality of the air photos and the scale used may have affected the DEM resolution, as the air photos may not have 
captured all topographic elements, such as ravines, localized bluffs, or small scale features. The North Pender DEM was derived from the 
air photos flown at a scale of 1:16,000, with 0.5 m vertical accuracy on open ground surfaces and 30 cm horizontal resolution. For those 
areas with extensive forest canopy, the elevation accuracy could vary by as much as half of the tree height. In addition, the elevation data 
(DEM)  does  not  include  mean  sea  level  for  North  Pender  Island  due  to  mean  sea  level  not  being  identified  at  the  time  of  the  air  photo 
flight. Accordingly, the minimum mapped elevation along the shoreline is 2m. Classified Steep Slopes Hazard areas smaller than 36 square 
metres  have  been  filtered  out  of  this  map,  the  resolution  of  these  areas  having  been  deemed  insignificant  to  the  potential  geological 
hazard.  
 
The  rationale  and  support  for  the  classification  of  Steep  Slopes  Hazard  designations  is  contained  in  the  recommendations  of  a report 
prepared  for  the  Islands  Trust by  Shane  Moore, P.  Geo.,  C.  N.  Ryzuk  and  Associates.  Copies  of  the  report  (C.N.  Ryzuk  and  Associates, 
Geological Hazard Mapping Project, North Pender Island, December 2009) can be obtained by contacting the offices of the Islands Trust.

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