Upon the expiration of the 30-day period mentioned in Chapter 4 of this part, an election shall be called and held by the board in that part of the drainage district affected by the assessment or the issuance of bonds, to determine whether the money necessary to pay the cost of the works and other expenses to be paid out of the assessment shall be raised by calls to be made upon the assessment in such installments as may from time to time be determined by the board, or whether bonds of the drainage district shall be issued in an amount equal to the amount of the assessment then remaining unpaid.