The detachment of territory from the district shall be deemed to relate only to the operations of the district subsequent to the order of detachment. Territory detached and all taxable property in that territory shall be and remain liable for the proportionate share of all bonded, warrant, and other indebtedness incurred by the district prior to the time of detachment. The proportionate share of the indebtedness of the district incurred prior to the order of detachment shall be borne by the detached territory and shall be computed as provided in section 40-1609, Idaho Code.