Automation of Six Visual Checks for DFIRM QA/QC 

Guidance for Resolving Errors 1301 & 1302 in the Six Checks Report

Check 1301: Invalid line type Multi-Hazard Flood 

Checks that the flood hazard line surrounding Special Flood Hazard Area polygons are coded with a valid line type. 

Check 1301 logic: 
If S_FLD_HAZ_AR SFHA_TF attribute is coded to “T” and the bounding S_FLD_HAZ_LN LN_TYP is coded 
as: “Floodway, Limit of Floodway, Limit of Detailed Study, Limit of Study, 1 PCT Annual Chance Flood 
Hazard, End of Spatial Extent, Zone Break, Apparent Limit, or Source Boundary” 

Then:
Correct – Please move to next check

Else:

An error will be returned as:

“Error 1301: The S_FLD_HAZ_AR polygon <ID> attributed as a Special Flood hazard Area is bound by an 
invalid S_FLD_HAZ_LN LN_TYP” 


Check 1301: Example 1 

Error is called because SFHA polygon is Zone A but surrounded by a line coded “0.2 PCT ANNUAL CHANCE FLOOD HAZARD” 

Auto Report will list the ID of the affected polygon, in this case FLD_AR_ID = ‘279’ 

To correct the error, flood hazard line ID 629 must be coded “1 PCT ANNUAL CHANCE FLOOD HAZARD” 

Check 1301: Example 2Check 1301: Example 24 

Check 1301 will also find flood 

hazard lines that overshoot a polygon boundary and overlap theline around the adjacent polygon 

In this example, the 0.2 PCT linearound the lower polygon extendsupwards past the polygon boundaryand touches the 1 PCT polygon 

A 25-foot tolerance was added to Check 1301-lines like this one will be allowed to pass 

Check 1301 will still be called if the overshooting line is longer than 25 feet 

To correct the error, the overshooting line will have to beclipped at the polygon boundary 


Finding Check 1301 Errors Step 1 

Note the FLD_AR_ID from the Auto Screen Report 

Finding Check 1301 Errors Step 2 

For ESRI ArcGIS Users: 

From the Select menu, Choose“Select by Attributes”

Double click on “FLD_AR_ID”, equals sign, and enter the ID number in single quotes


Finding Check 1301 Errors Step 3 

Zoom to Selected Feature 

If the wrong line type can be clearlyseen, then youknow what line to fix 

If the polygon ismore complicated, you can query forthe lines that bound it in the 
next step… 


Finding Check 1301 Errors Step 4

For ESRI ArcGIS Users: 

Go to the Select Menu 

Choose “Select by Location” 

Select features from the S_FLD_HAZ_LN layer that “share a line segment with” the S_FLD_HAZ_AR layer 

Use selected features (defaultselection) 


Finding Check 1301 Errors Step 5 

Open the attributetable for the S_FLD_HAZ_LN layer, show selected features 

Look in the LN_TYP column for invalid values (like 0.2 PCTANNUAL CHANCE FLOOD HAZARD) 

If there are manyincorrect lines, you can filter out the valid ones in the next step…. 

Finding Check 1301 Errors Step 6

For ESRI ArcGIS Users: 

Go to the Select Menu 

Choose Select by Attributes 

Select Layer, S_FLD_HAZ_LN 

Select Method, “Remove from current selection” 

Copy and paste the list of valid line types to remove: 

"LN_TYP" IN ( 'FLOODWAY', 'LIMIT OF 
FLOODWAY', 'LIMIT OF DETAILED 
STUDY','LIMIT OF STUDY', '1 PCT 
ANNUAL CHANCE FLOOD HAZARD', 
'END OF SPATIAL EXTENT', 'ZONE 
BREAK','SOURCE 
BOUNDARY','APPARENT LIMIT') 

Finding Check 1301 Errors Step 7 

Open the attribute table to see the remaining lines 

Finding Check 1301 Errors Step 8 

The 0.2 PCT line extends all the wayacross the AE zone. 

The line type needs to be recoded for this segment 


Finding Check 1301 ErrorsStep 9 

Sometimes Check 1301 can be caused by sliver polygons adjacent to the SFHA polygon. 

In this example, the0.2 PCT polygon is less that 0.1 mapunits wide. 

You can find these lines by followingthe next step…


Finding Check 1301 Errors Step 10

Clear all selected features 

Re-select the polygon ID you wishto examine 

Go to the Select Menu and choose Select by Location 

Select from S_FLD_HAZ_LN features that “share a line segmentwith” the S_FLD_HAZ_AR polygon 

Use selected features (defaultselection) 

Apply a buffer to the features inS_FLD_HAZ_AR 

Set buffer to 0.1 units 


Finding Check 1301 Errors Step 11

Open the attribute table to see the remaining lines 


Finding Check 1301 Errors Step 12

This sliver 0.2 PCT polygon andline should be trimmed to remove the error 


Check 1302: BFE line Undershoot/Overshoot

Checks that BFE lines extend to the Special Flood Hazard Area boundary 

Checks BFE lines in AE and AH zone polygons with no static BFEs 

Small overshoots and undershoots of less than 25 feet will be allowed to pass 

Check 1302 logic: 
If: S_BFE line is within +/-25 feet of the SFHA boundary

Then:
Correct – Please move to next check
Else:

An error will be returned as:
“Error 1302: The following S_BFE line (s) undershoot or overshoot the SFHA boundary by more than 25 feet”


Check 1302: BFE line Under/Overshoot Example 1 

This BFE line undershoots the SFHA boundary by more than 25 feet 

To fix the error, the line must be extended to the SFHA boundary 

Small undershoots or overshoots will be allowed to pass if they are less than 25 feet 


Check 1302: BFE line Under/Overshoot Example 2 

Check 1302 allows special cases to pass 

BFE lines that do not extend across the SFHA will still pass if the adjacentpolygon is notsupposed to have 
BFE lines 

The lines will passas long as they arewithin 25 of the polygon boundary inthis example BFE does not extend across the entire SFHA, but placement is correct since BFE lines do not appear in AO zones. 


Check 1302: BFE line Under/Overshoot Example 3 Map Modernization 

Check 1302 allows special cases to pass 

BFE lines that do not extend across the SFHA will still pass if they areinterrupted by ageneral structuresuch as a levee 

The lines will passas long as they arewithin 25 feet of the general structure 


Check 1302: BFE line Under/Overshoot Example 4 

Check 1302 can also be caused by BFE lines in a polygon that is not supposed to contain BFE lines 

BFE lines are only allowed in Zone AE or Zone AH with no STATIC_BFE value (notpopulated or -9999) 

BFE lines outside these areas will be called in Check 1302…. 


Check 1302: BFE line 

Under/Overshoot Example 4 Map Modernization 

BFE_LN_ID 355 is in a polygon coded 

0.2 PCT ANNUAL CHANCE FLOOD 
HAZARD. (FLD_AR_ID = 33) 

The BFE line must be deleted, or the 
coding of the polygon and the line 
bounding it are incorrect. 

Since Check 1302 allows a 25-foot tolerance for BFE placement, it must examine thepolygons around the end points to find theSFHA boundary. 

The check creates a 25-foot buffer around the BFE end points. If the BFE is placed correctly, the buffer will touch the polygon containing the BFE, and the non-SFHApolygon just beyond the end point. 

If it only touches the SFHA polygon containing the BFE, it is an undershoot. 

This data set is missing the Zone X area. Since the check cannot find the boundary, it interprets it as a BFE undershoot. 

To fix this error, the flood hazard area layer must cover the whole study, including the 
Zone X beyond the BFE end points.