@Don Chen have it done professionally with a survey and permit. 

I build in Charleston SC and flood maps are updated all the time.. and all the houses are first surveyed for height then built up high enough to allow water under them depending on location. in downtown Charleston that means 7 to 10 feet above grade before you have the first living space and everything is built on cinder block footers.. its looks like storm drainage as you described was designed to flow into the cored out streets and exit.. instead of underground..

Faster closing - no underwriting and other items like appraisals and surveys.

Do a market survey and check pricing and vacancy in nearby competition. 

Just 1 week before closing, the survey result shows that the actual plot size is 2.03 acres compared to 3.6 as shared in MLS.

Title is moot and not a big deal.. and in Texas its common to get fresh survey each time you buy and sell .. so she will want to do that..

CBRE, Marcus Millichap, etc also provide excellent cap rate surveys by region that you should read.

Someone correct my numbers, but I believe the survey results a few months ago revealed that like 70% of BP members were still working on their very first deal!

Lesson learned How was abstract of title, title search and survey done in 7 days?

I use survey monkey to record all the answers so that I have a record that I have asked every single person the same questions with the same criteria, don't want to get in to any Fair Housing troubles.