Floodplain Management

FEMA defines a floodplain as any land area susceptible to being inundated by floodwaters from any source.

The Flood Insurance Rate Map (FIRM) shows areas within the 100-year flood boundary, which are termed "Special Flood Hazard Areas (SFHAs)." A "100-year flood" does not refer to a flood that occurs once every 100 years, but refers to a flood level with a 1 percent or greater chance of being equaled or exceeded in any given year.  The SFHAs may be further subdivided into insurance risk rate zones (see below). Areas between the 100-year and 500-year flood boundaries are termed "moderate flood hazard areas." The remaining areas are above the 500-year flood level and are termed "minimal flood hazard areas."

Historically, about one-third of claims paid by the NFIP are for flood damage tin areas identified as having only "moderate" and "minimal" risk of flood.  Flooding in these often is the result of inadequate local drainage 25 systems, and such flooding sources with small drainage areas are generally not identified on FIRMS, but are a part of Flood Prone Areas.  The SFHAs are subdivided into flood hazard zones (insurance risk rate zones) according to the following criteria:   

• Zone A:  SFHAs subject to inundation by the 100-year flood.  Because detailed hydraulic analyses have not been performed, no base flood elevation or depths are shown. Mandatory flood insurance purchase requirements apply.  
o Estimated Base Level Engineering allows Bastrop to determine the base flood elevations and flood depths for areas on the FIRM designated as Zone A.

• Zones AE:  SFHAs subject to inundation by the 100-year flood determined in a Flood Insurance Study by detailed methods. Base flood elevations are shown within these zones. Mandatory flood insurance purchase requirements apply. (Zone AE is used on new and revised maps in place of Zones A1-30.) 

• Zone AH:  SFHAs subject to inundation by 100-year shallow flooding (usually areas of ponding) where average depths are between one and three feet. Base flood elevations derived from detailed hydraulic analyses are shown in this zone.  Mandatory flood insurance purchase requirements apply.

• Zone AO:  SFHAs subject to inundation by 100-year shallow flooding (usually sheet flow on sloping terrain) where average depths are between one and three feet. Average flood depths derived from detailed hydraulic analyses are shown within this zone.  Mandatory flood insurance purchase requirements apply. 

• Zone X:  These areas have been identified in the community flood insurance study as areas of moderate or minimal hazard from the principal source of flood in the area.  However, buildings in these zones could be flooded by severe, concentrated rainfall coupled with inadequate local drainage creates areas of high flood risk within these rate zones.  Flood insurance is available in participating communities but is not required by regulation in these zones.

o Estimated Base Level Engineering allows the City of Bastrop to determine the base flood elevations and flood depths for some areas on the FIRM designated as Zone X, and structures developed in these areas are required to elevate 2’ above the base flood elevation.

Special flood hazard areas are determined using statistical analyses of records of river flow, storm tides, and rainfall; information obtained through consultation with the community; floodplain topographic surveys; and hydrologic and hydraulic analysis. The detailed FIS covers those areas that are subject to flooding from rivers and streams, along coastal areas and lake shores, or in shallow flooding areas, but do not include areas of less than one square mile.

There are multiple ways to verify:

1. Search the property address in the FEMA National Flood Hazard Layer map, the FEMA Flood Map Changes Viewer, or use the estBFE Viewer.
2. Email plan@cityofbastrop.org your property information (address, BCAD property ID, and/or legal description) and ask if the property is in a floodplain.
3. Obtain an Elevation Certificate from a registered professional land surveyor.

The floodway includes the channel of a river/waterway and the adjacent floodplain that state standards specify smaller allowable increases.  FEMA requires the community to designate a floodway to avoid the possibility of significantly additional rise in base flood elevations.

Floodplain in areas that have been identified by different sources including but not limited to FIRMs (Special Flood Hazard Areas), Base Level Engineering (BLE) (Supplemental Flood Hazard Areas), Flood Studies (Community Determined Flood Hazard Areas), Letters of Map Change, and/or repetitive loss areas.

Depending on the area, yes, but the Flood Damage Prevention Order has provisions with specific requirements for each type of structure that is built within a flood prone area.  

Please contact the Planning & Development office to schedule a consultation to view your plans and to determine the best course of action to assure that your project will be reasonably safe from flooding.

A surveyor or engineer can certify that the proposed construction will meet the requirements of the City of Bastrop Flood Damage Prevention Order by preparing an elevation certificate.  Elevation certificates are required for residential development.

Three procedures have been established for changing or correcting a flood map.  They are called collectively Letters of Map Change (LOMC) and include:
• a Letter of Map Amendment (LOMA) 
• a Letter of Map Revision (LOMR) 
• and a physical map revision.