I am trying to sell a property I rehabbed that the HCAD had over-appraised on a lot they listed at 35,000 sf.  With public easements, the lot is more like 12,000 SF.  2/3 of the listed sf is a 45 degree slope heading down to White Oak Bayou.  

I think potential buyers are scared off by the property taxes, and when they see the property they are expecting to see a larger lot.  How do I go about donating the public easement part of the property to the flood control district to get it off my tax rolls?  This isn't a "home buyout," as I only want to donate part of the property without any structures.