Procedure for landslide investigations 
Not only must the presence or potential development of landslides be 
recognized, but the types and causes of movement must be identified so 
that preventive or corrective action can be taken. To accomplish this, 
the following steps are typically performed. 
l. Obtain aerial photography and other special coverage. Small-scale 
coverage for regional overview and large-scale coverage for detailed 
study are obtained from available sources. If landslides are already 
present, photographs taken both before and after the occurrence should 
be obtained to aid in locating causative factors that may have been 
obliterated by the slide. Special types of photography or imagery are 
acquired as needed. 
2. Review literature and maps. A review is made of existing topo- 
graphic maps, geologic maps and reports, water well logs, agricultural 
soil survey reports, and other literature to develop an areal concept 
of the area under investigation. 
3. Analyze the photography and other special coverage. The patterns 
on the photographs are analyzed, and landforms are identified and 
related to the areal concept developed from the literature review. 
A careful examination is made of all locations especially vulnerable to 
Slope movement. Existing and potential landslide sites are delineated, 
and a three-dimensional concept of the terrain is developed. In this 
step, a mosaic is usually prepared and landform and drainage maps are 
developed. Sites that offer the best opportunities for confirming or 
extending the information developed are selected for field verification. 
4. Perform field reconnaissance. A field reconnaissance of the area 
is performed to verify the three-dimensional concept developed in the 
earlier steps, to fill in information in questionable areas and to 
observe the surface features and details not determinable from other 
data sources. The type of landslide movement is classified from the 
available data and from a study of the surface features and crack 
patterns observed in the field. 
5. Conduct final analysis and plan field investigations. A final 
analysis of the photography is performed based on the results obtained 
from the field reconnaissance. A determination is made as to what 
additional information is needed to fully define the three-dimensional 
model of the site and what samples and test data are required to design 
the corrective procedures. 
6. Perform detailed field investigation. At this stage the landslide 
or landslide-prone areas are accurately delineated, the causative 
factors are determined, and the necessary field testing is performed to 
determine the physical and chemical properties required for the design 
of the corrective measures.