If the contractor shall make default and if there shall be a failure to collect all the damages from such contractor and the sureties upon his bond, and it shall thereby be necessary to raise a greater sum of money to complete the drainage works in accordance with the plans, or for any other unavoidable cause it shall be necessary to raise a greater sum to complete such drainage work, the board of viewers of the county in which the petition was filed shall prepare new assessment rolls upon all the lands in the project upon the original basis of classification of benefits, and increase the same in sufficient sums to equal the deficit thereby created, and the same shall constitute the new assessment rolls until changed according to law, and shall be certified to the county treasurer or treasurers as herein provided.