3735
The area 's topography is characterized by the broad alluvial plain of the Arkansas River valley and the moderately rolling slopes that rise to the higher lands on either side .
 location: Arkansas River
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 location: Arkansas River