ORS § 553.370
In the event that it is determined, after the construction of any works within a subdistrict, that any lands within the subdistrict are benefited and the benefits accruing to such lands were not determined by the board or by appraisal or the benefits determined by the board are less than the benefits actually accruing to the property, or in case any person makes use of or profits by the works within any subdistrict to a degree not compensated for in the original determination of benefits by the board or by appraisal, or in case the directors of the district find it necessary to take or damage any additional property, the directors shall petition the court for appointment of a board of appraisers to appraise or reassess the benefits accruing to any tract of land within the subdistrict or to appraise the damages to or value of any property taken. After the appraisers file their report, the court shall act thereon in the manner provided for the approval by the court of the original appraisal.
ORS 553.370