Assessments are made upon basis of benefits derived. Petersen v. Thurston, 161 Neb. 758, 74 N.W.2d 528 (1956).
Where board of supervisors of a drainage district assess property not within the district, and do not assess on basis of benefits derived, the order levying assessments is void and subject to collateral attack. Drainage Dist. No. 1 v. Village of Hershey, 139 Neb. 205, 296 N.W. 879 (1941).
Levy need not be confined to part actually overflowed if the whole is benefited. Nemaha Valley Drainage Dist. No. 2 v. Higgins, 90 Neb. 513, 134 N.W. 185 (1912).
Exact apportionment in detail is impossible, but it is sufficient if each tract as a whole is improved. Land appropriated for ditch must be excluded from land assessed. Nemaha Valley Drainage District No. 2 v. Stocker, 90 Neb. 507, 134 N.W. 183 (1912).