Full Opinion

IN THE COURT OF APPEALS OF IOWA _______________ No. 25-1105 Filed October 7, 2026 _______________ David S. Mercer, Kimberly S. Mercer, Mervin C. Anderson, Mary M. Anderson, David Bang, Bang Family Trust, Barak Brakke, Paul Levang, Paul PDJJ Levang Farms LLC, Leah R. Nelson Revocable Trust, and Matthew Olson, Plaintiffs–Appellees, v. Drainage District No. 72, Worth County, Iowa, and the Worth County Board of Supervisors, as its representative, Defendants–Appellants. _______________ Appeal from the Iowa District Court for Worth County, The Honorable Gregg R. Rosenbladt, Judge. _______________ AFFIRMED _______________ Robert W. Goodwin of Goodwin Law Office, P.C., Ames, attorney for appellants. Eldon McAfee, Julia L. Vyskocil, Nick F. Miller, and Keegan Cassady, of Brick Gentry, P.C., West Des Moines, attorneys for appellees. _______________ Considered without oral argument by Greer, P.J., and Buller and Langholz, JJ. Opinion by Buller, J. 1 BULLER, Judge. The Worth County Board of Supervisors (the Board) as trustee of Drainage District No. 72 (DD72) appeals the district court ruling that declined to consider several “amendment” reports and reversed the Board’s decision to annex certain property into DD72. Because the district court correctly declined to consider the amendment reports, and the engineering and annexation reports contained insufficient information to show annexation would materially benefit the land, we affirm. BACKGROUND FACTS AND PROCEEDINGS After years of disagreement among landowners over who was responsible for maintaining a private drainage ditch that drained into DD72 facilities,1 the Board became involved and hired an engineering firm to investigate repairs and make recommendations. The Board’s engineer recommended annexation of about 1,806 acres (Upper Goose Lake) into DD72. Afterward, the Board appointed the same firm to conduct an annexation study, which the same engineer drafted. The study found that “[t]he benefits derived are material in that the surface and/or subsurface drainage of excess waters from each parcel is discharged through and removed by existing DD72 facilities, which were designed in part to receive, and pass said excess waters to the district’s outlet.” Before a public hearing, several landowners filed written objections to the proposed annexation. Objections were also presented at the hearing on February 27, 2023, and the hearing was continued. The Board’s engineer 1 “A drainage district is a special governmental entity that manages water drainage in a particular area to enable more productive uses of farmland.” Iowa N. Ry. v. Floyd Cnty. Bd. of Supervisors, 29 N.W.3d 307, 308 (Iowa 2025). 2 submitted a response to the objections to clarify and reiterate the benefits to be received by landowners in the Upper Goose Lake annexation to DD72 facilities, and on March 20, the Board voted to annex Upper Goose Lake into DD72. Shortly afterward, the landowners retained their own engineer who recommended against annexation for Upper Goose Lake—except for about 46 acres—because the land would not materially benefit from DD72 facilities. The landowners’ engineer presented an extensive historical analysis of the local drainage infrastructure and concluded that the Upper Goose Lake lands would naturally drain without the private ditch’s connection to DD72 facilities. The plaintiffs appealed the annexation. At trial, both parties presented their respective engineers as expert witnesses. And the Board also introduced four “amendment” reports generated in the months following the annexation vote. The district court credited the landowners’ engineer’s testimony and declined to consider the amendment reports. The court found the Upper Goose Lake lands would not materially benefit from annexation, and that the Board’s report was not supported by sufficient information. The Board appeals. STANDARD OF REVIEW This case was tried in equity, so our review is de novo. Iowa Code § 468.91 (2023); City of Eagle Grove v. Cahalan Invs., LLC, 904 N.W.2d 552, 558 (Iowa 2017); Iowa R. App. P. 6.907. “In equity cases, especially when considering the credibility of witnesses, the court gives weight to the fact findings of the district court, but is not bound by them.” Iowa R. App. P. 6.904(3)(g). 3 DISCUSSION The Board argues the district court should have considered all the amendment reports as supplements to an expert witness report under Iowa Rules of Civil Procedure 1.508(3), 1.500(2)(e), and 1.500(5) “to have all available information.” But its argument misses the mark. The amendments here include information available at the time of the Board’s decision that the Board’s engineer failed to initially include. Cf. Belz v. State, No. 23-1611, 2024 WL 4615633, at *4 (Iowa Ct. App. Oct. 30, 2024) (explaining a second report on a different topic filed “well past” the report deadline should not be admissible under 1.508(3) or 1.500(2)(e) when the data was available during the drafting of the initial report). The duty to supplement is meant to “clarify issues prior to trial, avoid surprise to parties, and allow a complete opportunity to prepare for trial,” not bolster deficient reporting. Whitley v. C.R. Pharmacy Serv., Inc., 816 N.W.2d 378, 386 (Iowa 2012). We agree with the district court that the Board’s “amendment” reports are not actually supplemental. Second, as the district court noted, these reports were created after the Board had voted to annex the lands at issue and therefore had determined annexation would materially benefit the Upper Goose Lake lands. These ex post facto reports undermine the statutory safeguards which require the Board to review an engineer’s report and provide notice of the engineer’s findings to landowners. See Iowa Code § 468.120. The district court correctly declined to consider the amendment reports, and we also exclude them from our consideration. The Board also argues the district court erred by ruling the DD72 facilities did not materially benefit the Upper Goose Lake lands. It stresses that the lands materially benefit from the increase in drainage capacity 4 beyond its natural drainage. The Board’s engineer’s initial report summarized the material benefit as the drainage of surface and subsurface excess water through DD72 facilities. To annex land into a drainage district there must be evidence the land “will in all reasonable probability derive some special benefit from the improvement.” Zinser v. Bd. of Sup’rs of Buena Vista Cnty., 114 N.W. 51, 56 (Iowa 1907). But “when the topography of land would ensure surface waters drained off the landowner’s property naturally, a landowner must receive some benefit other than an outlet for surface waters to have a material benefit.” Blue Verbrugge Fam. Farms, LLC. v. Hamilton Cnty. Bd. of Supervisors as Trs. of Drainage Dist. No. 71, No. 22-1797, 2024 WL 1295075, at *3 (Iowa Ct. App. Mar. 27, 2024) (cleaned up). “A landowner may freely avail himself of the topography of his land, and may discharge his surface waters wherever gravitation naturally carries them, without further concern on his part as to where they go, for they are no longer his.” Id. (cleaned up). And the district court credited the landowners’ expert’s testimony that the Upper Goose Lake lands were separate from the DD72 marsh. Finally, we note a panel on this court recently found that the same material benefit language used here provided insufficient information to justify annexation. Id. at *1–3. We agree, and on our de novo review of this record, we affirm. AFFIRMED. 5