20260323
11584200
1.0
FALSE
FFRA_500_Year
-104.102385
-97.155148
28.196846
32.086463
1
-
-
Relationship
-
Relationship
-
Relationship
-
Relationship
-
Relationship
-
Relationship
-
Relationship
-
Relationship
-
Relationship
-
Relationship
-
Relationship
-
FFRA_500_Year_Subbasins
Relationship
002
Geographic
GCS_WGS_1984
Angular Unit: Degree (0.017453)
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20260223
15545700
20260223
15545700
150000000
5000
dataset
20260223
File Geodatabase Feature Class
Esri ArcGIS 13.3.0.52636
Flash Flood Risk Areas 500 Year
This layer represents the 500-year floodplain from the TWDB RFPG Flood Quilt, divided into 1-km pixels associated with the database.
<DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN STYLE="text-decoration:underline;">FFRA_Grid</SPAN><SPAN>: This unique identifier corresponds to a pixel in the associated shapefiles, and it is used to relate to the other tables within this relational database. </SPAN></P><P><SPAN STYLE="text-decoration:underline;">County_Name</SPAN><SPAN>: The county name</SPAN></P><P><SPAN STYLE="text-decoration:underline;">Visualization</SPAN><SPAN>: Distinguishes the priority of concern by hazard and exposure. High hazard outdoor and building exposures are presented first, followed by moderate hazard outdoor and building exposures, then the remaining features of the 500-year floodplain. The high hazard building exposures are further identified by flood severity categories where available in Bexar, Travis, and Williamson counties.</SPAN></P><P><SPAN STYLE="text-decoration:underline;">Include</SPAN><SPAN>: Determines indexes that corresponds to features that meet the described inclusion criteria.</SPAN></P><P><SPAN STYLE="text-decoration:underline;">Status</SPAN><SPAN>: Provides the simplest dataset for viewing areas that meet the criteria. “Include” corresponds to features that meet the described inclusion criteria, “Removed” corresponds to features that were removed due to exclusion criteria, and “N/A” identifies corresponds to features that never met any of the inclusion criteria.</SPAN></P><P><SPAN STYLE="text-decoration:underline;">Criteria</SPAN><SPAN>: Describes the criteria met that warranted the status described in Status Field. Criteria (1-8) describe the hierarchy of inclusion criteria, criteria (9-10) then describe the exclusion or removal criteria, and criteria (11) is the remainder of the 500-year floodplain that would be considered “N/A” in the Status Field.</SPAN></P><P><SPAN STYLE="text-decoration:underline;">Query</SPAN><SPAN>: Query used to symbolize the dataset.</SPAN></P></DIV></DIV></DIV>
This data was generated by AtkinsRéalis and WERC, using the Flood Quilt (2024) provided by Texas Water Development Board (TWDB) Regional Flood Planning Group (RFPG). Downloaded November 2025.
county
FFRA
Flash Flood
Flash Flood Risk Areas
Flood Quilt
Flood
floodplain
risk
hazard
<DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN STYLE="font-size:12pt">The FFRA is provided for the 30-county area at a spatial resolution of 1-kilometer by 1-kilometer for better computational efficiency as well as to align with input data with the coarsest resolution among those that were used in this study. In addition, the selection of the 1-kilometer by 1-kilometer pixel grid for processing FFRA can avoid confusion about the intent of the product – a finer resolution may give a false impression about the precision or intent of this study. This study is not intended to site sirens as part of outdoor warning siren systems but to identify flash flood-prone areas that warrant sirens. FFRA with a resolution of 1x1 kilometer can adequately serve as foundational information for identifying flash flood-prone areas that warrant sirens given the audible radius for outdoor warning sirens typically ranging from approximately 1 to 2 miles.</SPAN></P></DIV></DIV></DIV>
0.000000
0.000000
1
-104.102385
-97.155148
32.086463
28.196846
473913
EPSG
6.2(3.0.1)
FFRA_500_Year
Feature Class
473913
OBJECTID
OBJECTID
OID
4
0
0
Internal feature number.
Esri
Sequential unique whole numbers that are automatically generated.
Shape
Shape
Geometry
0
0
0
Feature geometry.
Esri
Coordinates defining the features.
FFRA_Grid
FFRA_Grid
String
100
0
0
SUBBASIN
Subbasin
String
49
0
0
County_Name
County_Name
String
20
0
0
Shape_Length
Shape_Length
Double
8
0
0
Length of feature in internal units.
Esri
Positive real numbers that are automatically generated.
Shape_Area
Shape_Area
Double
8
0
0
Area of feature in internal units squared.
Esri
Positive real numbers that are automatically generated.
Include
Include
Integer
4
0
0
Visualization
Visualization
String
75
0
0
Status
Status
String
25
0
0
Query
Query
String
150
0
0
Criteria
Criteria
String
75
0
0
Simple
FALSE
473913
TRUE
FALSE