Derwent is an unincorporated community in central Valley Township, Guernsey County, Ohio, United States. It is located near the southern border of Guernsey and Noble counties. Derwent lies in southeastern Ohio, a part of the Unglaciated Allegheny Plateau region. It is located about seven miles from Senecaville Lake. State Route 313 runs on th…Derwent is an unincorporated community in central Valley Township, Guernsey County, Ohio, United States. It is located near the southern border of Guernsey and Noble counties. Derwent lies in southeastern Ohio, a part of the Unglaciated Allegheny Plateau region. It is located about seven miles from Senecaville Lake. State Route 313 runs on the southern edge of Derwent, and its interchange with Interstate 77 is a little over 1 mile away. Major cities nearby include Zanesville and Marietta. The intersection of two cross-country highways is 8 miles away.