In a district which functions both as a diking and a drainage improvement district, the appraisers, if so directed in the order of the board appointing them, shall determine separately, in accordance with RCW 85.16.060 and 85.16.080, the special benefits accruing to the various properties within the district from the maintenance of the diking system and from the maintenance of the drainage system, and in such case their report shall contain separate schedules of the respective benefits accruing from the maintenance of the diking and drainage systems of improvement considered separately and, so far as may be, independently of each other.