Skip Ribbon Commands Skip to main content
:

Floods & Storms: Question and Answer

Purdue Extension > Extension Disaster Education Network > Floods & Storms: Question and Answer

Flood Question and Answer

If you have asked a question, and I haven't answered, please remind me by email at cain@purdue.edu.

Questions

I have tomato plants, cucumber plants and black raspberries that were all flooded out twice when water from a creek got out of its banks. None of them had any flowers or fruit on them at the time. Will any of these be safe to eat since they were flooded?

Can anyone comment on businesses that are advertising in the local newspaper for mold prevention and remediation? How do we judge them?

I have removed the water from my house. Is the air in my house safe?

I had water in the crawl space for the first time during the flood. The water is gone but there is a very musty smell. I even notice it when I come into the house. Should I put fans in the crawl space?

I've been told not to rebuild too quickly after the flood. Why?

How should I handle flooded food and vegetables from my garden?

If a vegetable or melon field is flooded, what is the risk level and what are the recommendations depending on the type of crop and stage of growth?

Is it possible to test the soil to show that it is free of pathogens?

Can I spray anything on the soil or on the crop to reduce risk of food-borne illness?

Does the bacteria enter into the tissue of the plant and then move to other parts of the plant that were not contacted or perhaps were not even present at the time of the flood water?

Can flooded fields be replanted to vegetables - if so, when, which vegetables, what should be done prior to planting?

My buyer requires third-party food safety certification; what should I do about flooded fields?

My greenhouse was flooded. I grow edible herbs in pots on the benches. The water did not contact the benches. Are the herbs safe?

Pots containing perennial small fruit crops (blueberries, grapes, brambles) were flooded. The entire plant was covered. What is the risk level? What if only the soil in the pot was flooded?

Should I do anything more than standard Good Agricultural Practices (GAPs) in the way of crop management or harvest/post-harvest handling?

Where is the line that demarcates 'legal but risky' from 'illegal'?

How can I learn more about Good Agricultural Practices (GAPS)?

When I get water out of my basement, how do I keep water out and repair the basement?

Is there any assistance (financial or otherwise) available to homeowners who are suffering losses due to flooding?

Is there federal assistance for farmers for building, structures (such as fences) and crop damage?


Question:
I have tomato plants, cucumber plants and black raspberries that were all flooded out twice when water from a creek got out of its banks. None of them had any flowers or fruit on them at the time. Will any of these be safe to eat since they were flooded? Any help you can give me on this would be greatly appreciated.

Answer:
Even though the tomatoes and cucumbers did not have flowers, there is still risk when the vegetables form. Contaminants that remain on the stem can be transferred to the tamato or cucumber fruit, contaminants in the soil may be splashed up, and cucumbers that touch the soil as they develop may be contaminated by organisms remaining in the soil. It is not safe to consume the produce.

Back to Top


Question:
Can anyone comment on businesses that are advertising in the local newspaper for mold prevention and remediation? How do we judge them?

Answer:
This is a difficult question to answer because contractors vary, but first remember not to be pushed into recovery decisions. The most important effort is to remove flood water-damaged materials and mud. Clean and dry out the house and all the materials.

One way to judge a contractor is to look at the products they use. Sealers used before the wood is dry will only trap moisture and molds and not remove them. This could result in long-term health issues. Some of the products used are common, mild disinfectants. Others are designed to inhibit mold growth. Science recommends removal - not just killing mold. A coating to deter regrowth while waiting for materials to dry can be useful. Experts recommend borate solutions on wood framing for the multiple benefits of termite, decay and mold resistance. But, if you kill but don't remove mold, the health hazard is still there. More important to invest in cleanup and speed drying than anything else.

The Indiana attorney general's office has useful information (PDF Link). Also here are some useful tips on how to find a reputable contractor.

Back to Top


Question:
I have removed the water from my house. Is the air in my house safe?

Answer:
You should assume that air quality is not good until all flood damaged items are thoroughly dried or removed from the house. Infants, pregnant women and people with health problems should avoid the flooded area until cleanup is complete.

The key is to remove all water, moisture and dried mud. Moisture in the wood can contain microorganisms and that can make you sick over the long run. Be sure to remove all materials that were contaminated by the flood waters that can't be cleaned, dried out and repaired. While cleaning and removing objects, wear a protective mask. Wash your hands with soap and uncontaminated water thoroughly and often as possible. This is especially important before handling food, eating, or smoking. If possible, use an antibacterial soap on your hands. Avoid biting your nails. Do not use combustion devices designed for outdoor use indoors. Returning your home to normal will be difficult and will take time.

These publications have much more detailed information that will help:

Back to Top


Question:
I had water in the crawl space for the first time during the flood. The water is gone but there is a very musty smell. I even notice it when I come into the house. Should I put fans in the crawl space?

Answer:
Moisture problems in the walls, crawl space, or attic can lead to serious pest problems, such as wood-boring beetles and wood-decaying fungi in the floor joists. Mold and mildew growing on wood or insulation can also attract nuisance pests, such as plaster beetles, which can slowly build up in numbers and become a chronic problem. Make sure foundation vents open properly and are clear of debris. Remove standing water from the crawl space as soon as possible. Increase ventilation to the crawl space. This can be a simple matter of opening the crawl space door or using a fan to pull air OUT of the crawl space, assuming that weather conditions (and availability of electricity) allow you to do so.

(Source: North Carolina State University - http://www.ces.ncsu.edu/disaster/factsheets/pdf/moisture.pdf)

Back to Top


Question:
I've been told not to rebuild too quickly after the flood. Why?

Answer:
Wood submerged in water will absorb a large amount of water. Rebuilding too quickly after a flood can cause continuing problems such as mold growth, insect infestations, and deterioration of the wood and wall coverings.

How long until it's dry? It may take weeks for the wood to be adequately dry to close a wall. The drying time will vary depending on the initial moisture content and the drying conditions.

How can I tell if it's dry enough? Test it with a wood moisture meter. Wood should have a moisture content of less than 15% before drywall, paneling or other coverings are placed on the wood. Do-it-yourselfers may be able to borrow or rent a meter from a hardware store or a lumberyard. Some county Extension offices have meters that can be checked out. If a contractor is doing the work, homeowners should have the contractor verify with a meter that the wood is dry.

(Source: EDEN - http://eden.lsu.edu/Topics/HumanHealth/Mold/Pages/default.aspx)

Back to Top


Question:
How should I handle flooded food and vegetables from my garden?

Answer:
Throw out most food, because floodwaters can contain a host of bacteria that may make the food unsafe or cause it to spoil. When I doubt, throw out food that may have been damaged or spoiled in the flood.

Commercially-canned foods are usually safe after being in flood waters if the metal can appears undamaged. Cans should be discarded if they are swollen/bulging at the can ends, rusty, creased or dented in the can seam/lid areas, or crushed. Undamaged cans still must be washed and sanitized before they are opened and used. For additional safety, thoroughly cook the canned food before eating it.

To clean and sanitize cans: Food from the garden is best handled with caution. It's risk to eat any of the produce, so discard it for safety's sake.

(Source: The First Steps to Flood Recovery)

Back to Top


The following is from Liz Maynard, Regional Extension Specialist, Commercial Vegetable and Floriculture Crops at Purdue University

Question:
If a vegetable or melon field is flooded, what is the risk level and what are recommendations depending on the type of crop and stage of growth?

Answer:
Risks can be described as follows:

Back to Top


Question:
Is it possible to test the soil to show that it is free of pathogens?

Answer:
Testing the soil is not a consistent method for determining the risk of microbial contamination; however, it may be useful for determining the presence of chemical hazards. Soil often contains the microorganisms that we use as indicators of fecal contamination and the numbers are not useful unless you know their relative levels prior to the flood. Trying to rely on a test to assure the soil is not contaminated would be very risky.

Soil testing for chemical hazards should be discussed with local health and agricultural specialists who can make you aware of hazards suspected in your region.

Back to Top


Question:
Can I spray anything on the soil or on the crop to reduce risk of food-borne illness?

Answer:
No, there are no sprays that would be appropriate for either the soil or the crop to reduce the risk. Any sanitizer would become ineffective based on the level of organic material present. And washing does not eliminate pathogens, so recommendations focus on reducing the risk by discarding affected crops, incorporating, planting a non-food crop and incorporating again next spring. If a field frequently floods, using it solely for agronomic or non-edible ornamental crops is recommended.

Back to Top


Question:
Does the bacteria enter into the tissue of the plant and then move to other parts of the plant that were not contacted or perhaps were not even present at the time of the flood water?

Answer:
That is a possibility. We have seen evidence in research that microorganisms could be drawn into tissues of non-woody plants and potentially transferred to produce this way. We cannot prove at this point that this does happen in field conditions; however, the risk that it could is considered great enough that we do not recommend harvesting produce for fresh market from plants that have been affected by a flood. Incorporating the top layer of soil, growing only nonfood crops and waiting until the following spring for planting crops intended for food is recommended.

Back to Top


Question:
Can flooded fields be replanted to vegetables - if so, when, which vegetables, what should be done prior to planting?

Answer:
Fields that have been flooded should be treated as if they had been treated with uncomposted manure. They are considered a very high risk for contamination with microorganisms that can cause food-borne illness as well as potentially harmful chemicals washed in from other areas.

With manure we recommend incorporation and a minimum of 120 days between incorporation and harvest. Even with this amount of time, a risk for fecal contamination could still exist. Much less risk can be achieved via incorporation and planting with a cover, agronomic, or non-edible ornamental crop and incorporating again pre-planting the next season.

Back to Top


Question:
My buyer requires third-party food safety certification; what should I do about flooded fields?

Answer:
Contact the fresh produce safety certification company that you will be working with. They can let you know what practices they specifically recommend and the t ypes of documentation they would expect to see. Often this involves writing out the steps you take to discard food affected produce, and how you work with the affected fields to reduce the risk of microbial contamination. At this time, each audit or certifying company has its own standards and it is best to be certain of what those are before the auditor comes out.

Back to Top


Question:
My greenhouse was flooded. I grow edible herbs in pots on the benches. The water did not contact the benches. Are the herbs safe?

Answer:
If you can assure absolutely no contact with the flood waters (including splashing) then your risk for direct microbial contamination is not higher than it was before. However, be aware that the greenhouse itself has been contaminated so your risk for indirect contamination of the herbs is greater. Steps should be taken to clean and sanitize the greenhouse with special care given to avoid splashing flood residue onto the produce or inadvertently transferring microbial contamination through hand or glove contact.

Back to Top


Question:
Pots containing perennial small fruit crops (blueberries, grapes, brambles) were flooded. The entire plant was covered. What is the risk level? What if only the soil in the pot was flooded?

Answer:
These plants are at a very high risk for microbial contamination. Fruit from these plants should be discarded this season to reduce your risk. Even if only the soil was affected there is at least a moderate risk that the contamination could lead to food-borne illness. It would be like side dressing with manure slurry. A minimum of 120 days from contamination to harvest is needed and a full season is preferable.

As for ornamentals, as long as they are not going to be consumed they are okay to be in ornamental gardens. Be sure to wash your hands well with soap and clean water after handling plant material or potting mix that has been exposed to flood waters.


A question that continues to arise is what growers should do to remove the residue that is left behind on ornamentals:
Horticultural approved wetting agents or surfactants at the lowest possible rates can be used to try to remove some the flood water residue left on leaves (i.e. CapSil). For this situation, The Scott's Company recommends using CapSil at a rate of 100 ppm with water (distilled or RO if possible) and then rinsing the leaves off again with water. This may help take some of the residue, but not all. Plants should be treated on a plant by plant basis to test for phytotoxicity. It is important to remember that no studies have been conducted to see if wetting agents or surfactants are effective for this purpose. Remember to follow labels closely and contact your distributor for questions.

An alternative would be to use some of the approved insecticidal soaps (Safer soaps, Bonide Insecticidal soap, SMC Premium Quality Leaf Wash, etc.) that we know are safe on plants. These can be applied by back pack or hand sprayer. Again, each plant species needs to be treated on a case by case basis, as phytotoxicity could be different between species.

Treat plants with the insecticidal soap to run off, allow it to sit for a few minutes to dissolve the residue and then apply water with a separate sprayer to rinse the residue off. This may not be feasible except for high value plants due to how labor intensive this could be. We discourage the use of soaps not approved for use on plants (i.e. dish or hand soaps) as this will influence the media pH and will only lead to more problems.

As far as the water molds are concerned, treatment with Subdue Maxx (Mefenoxam) or any of the phosphorous acids (Aliette, Agri-Fos, Vital, Biophos etc) will help prevent infection by Phytophthora, Pythium, etc. Of course, label directions must be followed. If crops or crop areas were under water for any extended period, prophylactic treatment with Subdue, followed by monthly follow-up with say Agri-Fos, should minimize the risk of infection.

(Source: Janna Beckerman, Roberto G. Lopez, and Liz Maynard, Purdue Extension)

Back to Top


Question:
Should I do anything more than standard Good Agricultural Practices (GAPS) in the way of crop management or harvest/post-harvest handling?

Answer:
As stated above, the crop and field should be treated as if they had been treated with uncomposted manure. In most cases, that means discarding the crop, incorporating, planting a cover or agronomic crop, incoporating again and using the field the following season. Beyond that careful adherence to Good Agricultural Practices throughout production, harvest and post-harvest is very important.

Back to Top


Question:
Where is the line that demarcates 'legal but risky' from 'illegal'?

Answer:
The FDA focuses on whether there is a probability that a food has become "adulterated." Adulteration is the term used to state that something has happened to the food to cause it to be injurious to health. The FDA clearly states that fresh produce that has come in contact with flood waters is considered to be adulterated. That puts any grower trying to salvage a crop from a flood in the territory of engaging in violating FDA regulations. Legal but very risky behavior is harvesting from plants that had not set prior to or during the flood or from crops planted immediately after the flood.

Back to Top


Question:
How can I learn more about Good Agricultural Practices (GAPS)?

Answer:
Excellent GAPS resources are available online at the National GAPS website. "Food Safety Begins on the Farm Growers Guide" and "Food Safety Begins on the Farm Grower Self-Assessment" are great places to start. The FDA website is updated regularly and inclues the "Guide to Minimize Microbial Food Safety Hazards for Fresh Fruts and Vegetables." Growers of tomatoes, melons, and leafy greens may also consult specific guidelines for those crops, available from the U.S. National Food Safety Program website.

Also, the USDA Risk Management Agency has partnered with Mid-American Ag and Hort Services, Inc. this year for a Fresh Produce Food Safety Initiative through September 30, 2008. The initiative provides for phone consultations as well as free on-farm food safety consultations. For more information call Deanne Mause at (419) 724-2930 or visit the website at http://www.midamservices.org. Additional information on Good Agricultural Practices may also be found at the Center for Innovative Food Technology.

Back to Top


Question:
When I get water out of my basement, how do I keep water out and repair the basement?

Answer:
If there is a large crack in the basement wall that is letting in groundwater, there is likely a structural problem. This can occur when the reinforcing in the basement walls is not able to withstand the inward pressure from high groundwater. It can even be made worse by having a dry basement (versus a flooded basement), since there is not a compensating pressure in the basement pushing out. My first reactions would be:
  • To handle future rainfall, install drainage outside the house to make sure water from roof downspouts is conducted well away from the building, either via a pipe sized to handle the flow (a 4" plastic pipe should be able to handle about half of the water coming off a typical residential roof (most plastic pipe must be buried to keep UV rays from the sun from making it brittle), or with a ¼"/ft slope in the first 25 feet (at least 6 inches in the first 25 feet) next to the building. Use diversion ditches or swales to route any surface water well away from the house as necessary.
  • Have a reputable contractor or structural engineer take a look at any basement wall that has large cracks or appears to be out of alignment to make sure the foundation or basement wall are still sound. This could be expensive so get a second opinion. It is doubtful that any type of patch on the "inside" of the basement wall could make much of a difference if there is a high water level (and high hydrostatic pressure) on the outside of the wall. Any excavation around the outside of the basement wall will have to wait until the ground has dried.

(Source: Don Jones, Professor and Purdue Extension Agricultural Engineer In Agricultural and Biological Engineering at Purdue University)

For more information:

Back to Top


Question:
Regarding flood assistance: Is there any assistance (financial or otherwise) available to homeowners who are suffering losses due to the flooding? We just received a call about this today.

Answer:
Groups like American Red Cross, Salvation Army, United Way and faith-based organizations are providing food, shelter, and water. In certain cases, people can get temporary assistance for alternate housing. They should check with their American Red Cross.

Longer-term, there will be a massive volunteer effort set up in Indiana to assist people with rebuilding. That effort is to be overseen by the State of Indiana and the Indiana Voluntary Organizations Active in Disaster (INVOAD). We should know more this week. As time progresses, please check www.invoad.com.

If the state receives a federal declaration for individual assistance, there will be more financial assistance. It is too early to suggest details.

Back to Top


Question:
Is there federal assistance for farmers for building, structures (such as fences) and crop damage?

Answer:
The State of Indiana has low-interest loans; go to the website for more information. The Farm Service Agency has disaster assistance.

Back to Top