Is the owner looking for an estimate of the impact? Or just a lower value? Is this appraisal for court for evidence of damages. You can do the damage / detrimental condition appraisal without seeing the flood stage, but you'll need to have the appropriate hypothetical / extraordinary assumptions based on what you're told. Then if it's going to court you're report will be undermined by the uncertainty of the nature and location of the damage. If the owner is serious, they need to provide you with something to hang your hat on that justifies any assumptions about the extent of flooding. There might even be liability issues that impact what the neighbor is responsible for that could affect details of the assignment. Photographs, a log of how often it happens, how deep it gets, report of odors. A hydrologist's report would be best. Something though would be better than just assumptions. You can still produce the appraisal without firsthand eyes on it if you include properly described assignment conditions (HC/EA). If it's headed for court, full before and after, tons of support for every adjustment. Flooded sales will be hard. You'd want sales that experienced similar intermittent flooding, of course. It would be more reflective if the flooding was not an expected characteristic, perhaps. That is, you could look for similar sales with flood plain acreage, but there could be an expectation by purchasers that flooding happens that doesn't fully capture impact. Particularly the septic odor issue.
That's a real research heavy assignment.
As for the legal aspects, there is definitely issues that are outside the expertise of typical appraisers. It's not for you to decide if there is a case or not. When I get involved in any kind of assignment where the appraisal is likely a court room bound exhibit with me in the hot seat, I ask the owner, first thing, if they are working with an attorney.
This can become important, especially if there are complexities about the proper method of appraisal. If the owner does not have an attorney, and they really plan on using it in court I strongly advise they retain one. If they have one, I request that the property owner stop communications with me, and tell their attorney to contact me, with the intention of having the attorney engage me, with the attorney as the client. Few reasons for this. One, if it's going to court, the attorney will understand the problems the appraiser faces. Second, if other experts are needed to supply you with info, like a hydrologist, the attorney will understand, and he'll need them as witnesses as well if you need them to do your work. If there is a case, its going to have to cost less than all the expert fees, so there might need to be some preliminary appraisal work to gauge that aspect. The attorney will also have any liability issues figured out, and they can explain anything that might affect assignment conditions. All of this activity requires conversation. It also can require the appraiser being asked questions regarding different valuation methods, the existence of sale, etc. You can have these discussions with property owner, but directly with the attorney reduces back and forth. But most importantly, any thing you and the property owner talk about is discoverable. You have some off the cuff talk about some aspect of the damage that you were speculating about, and the owner can be questioned about, say something that wasn't what you said, next thing you know the court thinks you're , a hired gun. Keep all the discussions with the attorney / client, and those discussions have attorney / client privilege. No discussions can be discoverable.
I would be circumspect about this one. Real tough finding sales, lots of additional supporting data, two scenarios, court room fees, but also exposure if you're not comfortable. I would right off suggest that if this isn't some pretty good impacts that the fees are going to top out impact; another good reason to get the attorney involved. But if you're game, start calling and emailing all your contacts and pouring over those lead sheets and be ready to go back in time and spread out geographically.
As an example, I examined the impacts of a landslide near a SFR at the top of a cliff / embankment that collapsed after a construction company had dumped removed soil from other sites over the bank. They had permission to dump, but the insurance company was required to pay the owners for any loss in value because of the known slide. It had even been remediated to some extent, but the owners were claiming a lot just for the known issue. stigma essentially. I looked all over the state and found five sales at sites with similar remediated slides. But they were all totally different building styles and sizes and not in the same markets. I had to essentially do mini-valuation studies on each sale to see how much each sale was impacted and apply the reconciled indication to the subject in the after. I needed like 30 sales for the after. I think unless you have some sales you know of that this will require a far and wide search. Proceed with caution!
Fortes fortuna adiuvat, sed cacas accidibit!!
