Water contamination during urban flood events can have a negative impact on human health and the environment. Prior flood studies lack investigation into how GIS can map and analyze this at a large scale (cadastral) level. This  thesis  focused on how GIS can  help map and analyze water contamination risk in urban  areas  using  LiDAR  elevation  data,  at  a  large-scale  (cadastral)  level,  and  symbology  and  flood classification  intervals  specifically  selected  for  contamination  risk.  This  was  done  by  first  completing a literature review about past research and studies  of similar scope. Based on  the findings, a method to map and analyze water contamination risk during sea-based flood scenarios was tested in the Näringen district of Gävle, Sweden. This study area was investigated and flood contamination risk maps were produced  for two different  flood scenarios which illustrated  which properties are vulnerable to flooding and at what depth, what their contamination risk is, and if they are hydrologically connected to the ocean.  The findings from this investigation  are that this method of examining water contamination risk could be useful to planning officials who are in charge of policies relating to land-use. These findings could help guide landuse  or  hazardous  material  storage  regulations  or  restrictions.  To  further  research  in  this  topic,  it  is recommended  that  similar  studies  are  performed  that  use  a  more  detailed  land-use  map  which  has information  on  what  type  and  quantity  of  possible  contaminants  are  stored  on  individual  properties. Furthermore, flood modeling should be employed in place of the flood mapping which was conducted in this thesis.