This section details the computational procedures used by HEC-FIA to calculate agricultural damage at a single crop cell. The procedures assume inundation durations throughout the project area are known and have already been added. Additionally, the procedures assume that crops are planted at the first available date after flooding and that crops will be planted immediately before an event (meaning that weather forecasting is not taken into account). The computational procedures are:
- Determine what type of crop the cell represents.
- Determine the arrival date and time of flooding for the crop cell.
- Determine the duration of flooding for the crop cell.
- Based on the arrival time and duration, determine if planting dates are impacted or if the crop is damaged before harvest.
- If damaged during the growing season, determine if the duration is longer than the longest duration damage curve; if so, the farmer loses all value placed in the field so far. The loss is equivalent to the marketable value minus harvest costs, prorated by total value input to the field to that point in time.
- If flooding limited the ability to plant and the farmer was unable to plant the preferred crop, the secondary crop will be used, and the loss will be the total marketable value for the secondary crop less harvest costs, minus the total marketable value for the primary crop less harvest costs.
- If the flooding made the farmer plant later than the first day of the season for the primary crop, but the farmer was able to plant the primary crop, the damage is based on a reduction in full yield due to late planting. This procedure is equivalent to the total marketable value less harvest cost, times one minus the percent loss due to late planting.
- Calculate the loss for each crop cell in the inundated area using the process described above and output the crop type, location, duration, and total damage for each crop cell damaged.