March 1, 2023

What are the Best Management Practices On-Farm After a Flood?

On Feb. 1, 2023, Western Growers, in collaboration with the California Department of Food and Agriculture, held a webinar titled “On-Farm Flood Management and Response.” The webinar was offered to answer important flood management questions and was presented by Dr. Ali Stickland, FDA Biologist; Dr. Erin Leigh DiCaprio, Associate Professor UC Davis Cooperative Extension; Vivian Soffa, County Executive Director Farm Service Agency; and Angie Ramirez, Food Safety and Organic Compliance Manager, Triangle Farms.

The speakers addressed best management practices and mitigation strategies that may be applied on-farm after a flood event. They also discussed technical resources and emergency disaster assistance programs that can help farmers address flood related challenges.

Here are important learnings in Q&A format:

How does the FDA define flooding?

Flooding is the flowing or overflowing of a field with water outside a grower’s control. Pooled water (for example, after rainfall) that is not reasonably likely to cause contamination of the edible portion of fresh produce is not considered flooding.

What environmental factors and commodity characteristics should growers consider when evaluating the impact of flooding to crops?

Consider the following when conducting a flood assessment:

  1. The source of flood water (runoff from adjacent land use, overflow from nearby stream, overflow from nearby irrigation canal, or pooling from overhead rain)
  2. Consider the type of crop and whether edible portion of the crop has potentially contacted flood water—edible portion is close to ground or in contact with flood water (spinach/lettuce) or edible portion is on a stalk, away from and not in contact with flood water (broccoli/cauliflower/artichoke). In some cases, your crop may be too young to have any edible portion developed. In this case, the risk of contamination would be considered low.
  3. Stage of growth (very young with no edible crop or mature crop, close to harvest)
  4. Level of inundation—how flooded is the field/crop?
  5. Duration of flooding—how long before the water receded from the field?
  6. Results of testing (water source, soil, etc.)

After considering these factors, a food safety professional should assess the level of impact and mitigation and management strategies.

What mitigation and management strategies should growers implement after a flood event?

Growers should consider the following mitigation strategies post-flooding to minimize the risk of cross contamination:

  1. Segregate flooded crops from non-flooded crops using visible markers such as flags
  2. Establish a 30-foot buffer between flooded and non-flooded areas
  3. Avoid movement of people/equipment between flooded and non-flooded areas
  4. Where movement can’t be avoided, use sanitation protocols to prevent cross-contamination

Protect wellheads and other water sources. If water sources have been impacted, take appropriate corrective actions and test the water source before use to verify water quality is suitable for intended use.

Who can growers contact for assistance with flood damage assessment?

Growers can contact their local Farm Service Agency, extension specialists and agricultural trade associations for assistance. Western Growers and other entities have online resources:

     Assistance Resources for Farmers Impacted by Recent Flooding | Western Growers (

How long must a grower wait to replant a crop after flooding has occurred? What are the requirements for conventional crops? What are the requirements for organic crops?

Per FDA guidance, a waiting period depends on conditions, but state/LGMA/research recommendations are to wait 30-60 days to allow the soil to dry out. This wait period can be shortened through soil testing, allowing growers to plant earlier.

What labs and methods can I use for soil testing?

Contact local labs to determine if soil testing services are provided and to confirm they are using validated methods. Review internal lab protocols where applicable. For example, if AOAC validated methods are not available, review the lab’s internal validation protocols. Work with your lab to determine how to collect your soil sample.

When should a soil sample be collected post-flooding? How long should I wait before collecting a soil sample?

Growers should allow the soil to sufficiently dry before collecting a soil sample. Growers can work the soil to expedite the drying process. Equipment used to work the soil should be properly sanitized after use to prevent cross contamination.

Can I divert my flooded crop to animal feed?

In certain cases, yes. Crops must be tested for mold, bacteria, chemicals and heavy metals. Contact the public affairs specialists located at your nearest FDA field office for more information.

What are the possible contaminants in floodwater?

Flood water may contain:

  • Microbiological pathogens
  • Chemical contaminants (pesticides, heavy metals, petroleum products)
  • Sewage from nearby treatment plants

Although organic production wasn’t specifically covered in this webinar, here are some commonly asked questions related to the impact of flooding to organic crops.

Are certified organic lands no longer organic after inundation?

Any parcels flooded will maintain their certification until surrendered, suspended, or revoked. Crops on the parcel may not be eligible for sale as organic if prohibited materials were in the flood water.

What needs to be done to re-certify organic land after flood inundation?

Growers whose farms have been flooded and are concerned that prohibited materials may have been in the flood waters should notify their certifier as soon as possible. Certifiers will work with growers to determine the potential for contamination and next steps. In general, certifiers view unintended water from flood as a drift situation and would require that any contaminated crop not be sold as organic but most likely there would not be a requirement for a three-year transition. However, corrective actions should be evaluated on a case-by-case basis to make that determination.

What about food safety concerns with this inundation, such as the introduction of feces to waters, that may impact microbial loads (e.g., E. coli outbreaks associated with crop)?

All crops directly contacting flood waters and 30 ft. around cannot be harvested for human consumption, and growers can’t replant for 60 days unless soil test results can determine it’s free from pathogens—then growers must wait 30 days before replanting.

What should I do if I am unclear about next steps with my organic crop post-flooding?

Growers should contact their certifier and provide details about their specific situation. Certifier representatives will provide guidance that is specific to each situation.