What are benchmark, datum, and datum types?
A benchmark is a fixed point with a reference measurement associated to it and an elevation is the measurement of a distance above the set point. So a concrete monument can be at 18 and the finish floor of a dwelling is 3 feet above the marker making the finish floor elevation to be 21. Datum is an assigned standard measurement associated to the reference marker; similar to how a foot is associated with Standard English and a meter is metric. There are three different datum references: Mean Sea Level (MSL), National Geodetic Vertical Datum of 1929 (NGVD29) and North American Vertical Datum of 1988 (NAVD88). The original Flood Insurance Rate Mate (FIRM) were developed using NGVD 1929 datum, but all Chatham County FIRM dated September 26, 2008 and later are based on NAVD 1988. The change of datum is a primary reason for the decrease of Base Flood Elevations on the 2008 FIRM maps. Bench mark elevations relative to NAVD 88 are available from NGS through the World Wide Web at National Geodetic Survey. A rough conversion of NGVD to NAVD in Savannah is by subtracting .93’ from NAVD 29 elevation.

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1. What else can I do to prevent my house from flooding?
2. What is the difference between a Flood watch and Flood warning?
3. How do ponds prevent flooding?
4. What is the difference between a Retention Pond and a Detention Pond?
5. What is compensatory Storage?
6. Why can’t hydrostatic vents be used in the VE zone?
7. What are some of the main construction tips for the different zones?
8. How can I remove my property from the Floodplain?
9. What are benchmark, datum, and datum types?
10. I live in a low-risk flood zone. Do I really need flood insurance?
11. What is the Substantial Damage | Substantial Improved (SD/SI) aka “50% Rule” and Pre FIRM?
12. What is the Coastal Barrier Resources System (CBRS)?
13. What are the different Flood Zones and Risks?
14. What is a Freeboard?
15. What is the difference between Base Flood Elevation (BFE) and Design Base Flood Elevation (DBFE)?
16. What is a 100 year or 500 year storm event?
17. What is the Community Rating System (CRS)?
18. What is Increase Cost of Compliance (ICC)?
19. What is the National Flood Insurance Program (NFIP)?
20. What is the difference between the “Floodplain” and the “Special Flood Hazard Area (SFHA)”?
21. What is the City of Savannah’s Community Number?
22. Do marshes and other vegetation prevent flooding?
23. What is the Preferred Risk Policy (PRP)?
24. Is flood damage from wind-driven rain covered?
25. Can “north-eastern” winds affect flooding?
26. If I live in a flood zone but my finish floor is above the BFE, do I still need flood insurance?
27. Can I get flood insurance if I do not live in a High Risk Area?
28. Can I get flood insurance if I'm renting a property?
29. What types of property may be insured against flood loss?
30. Does my policy go into effect once a payment is made?
31. What is Flood Insurance?
32. What causes flooding in Savannah?
34. What is the Flood Insurance Rate Map (FIRM) used for?
35. Where can I get More Information?
36. How do I know if I am at risk of flooding?
37. What kinds of property are not insurable under the NFIP?
38. What are FIRM Panels and how many are there?
39. What is the purpose of an Elevation Certificate?