When such district as contemplated in section 468.124 and the new improvement therein shall include the whole or any part of the former improvement, the commissioners, for classification of lands for assessment of benefits and apportionment of costs and expenses of such new improvement, shall take into consideration the value of such old improvement in the construction of the new one and allow proper credit therefor to the parties owning the old improvement as their interests may appear. In all other respects the same proceedings shall obtain as are provided for the original establishment of levee and drainage districts.
Iowa Code § 468.125
89 Acts, ch 126, §2