FEMA Out-by-LiDAR

 

Using LiDAR For Map Amendments  

LiDAR data can replace the requirement to submit elevation information  

certified by a licensed land surveyor or professional engineer, which can create  

a cost savings for property owners. However, LiDAR data may be less accurate  

than certified elevations and may not capture the full risk for the building or  

lot.  

For more information on the standard LOMA process and requirements,  

please refer to How to Request a Map Amendment Guide.  

DOES MY COMMUNITY HAVE LIDAR?  

Not all communities have LiDAR data available. Talk to your floodplain administrator to find out if your  

community has LiDAR data.  

To be used in a LOMA request, LiDAR data must meet or exceed the U.S. Geological Survey (USGS)  

Quality Level 3 accuracy requirement. To learn more about this requirement, please use the USGS  

LiDAR Base Specification Guide.  

The USGS plans to collect high quality LiDAR data across the United States using a 3D Elevation  

Program (3DEP). For more information on the 3DEP program and current USGS LiDAR availability,  

please visit their 3DEP webpage.  

WHEN LIDAR CANNOT BE USED  

There are situations when LiDAR cannot be used in a LOMA request. These include applications involving  

the following:  

• Buildings or lots elevated using fill  

• Buildings or lots in the regulatory floodway  

• Buildings or lots in Coastal High Hazard Areas (Zone V, VE, or V1-V30)  

• Buildings or lots in Zone AO, AR, or A99  

• Buildings under construction. LiDAR would need to show that the lot or portion of the lot on which  

building will be located is above the Base Flood Elevation (BFE)  

• Conditional determinations  

• Electronic LOMAs (eLOMAs)  

• Potential violations identified through the LOMA process  

• Physical changes to the flooding source/Special Flood Hazard Area that require revisions to the  

Flood Insurance Rate Map  

• Requests to supersede previously issued LOMAs based on certified elevation data  

Additional information about LiDAR requirements for LOMAs is available in the  

MT-1 Technical Guidance document.  

WHAT NEEDS TO BE SUBMITTED WITH MY APPLICATION?  

When requesting a LOMA using LiDAR data, you must submit a paper map or digital PDF that displays:  

(1) an overlay of the LiDAR contours (lines of equal elevation), or  

(2) an overlay of the LiDAR points (points with specific elevations).  

Either overlay must include an aerial image of the building or lot with at least one street intersection  

shown on the map.  

The map must also have:  

• Scale and North arrow  

• Source of the LiDAR, including public website  

address. LiDAR must be provided by a Federal,  

State, or local government agency.  

• Address or Assessor’s Parcel Number (APN)  

for the building/lot  

• LiDAR accuracy information  

• Clearly identified building and/or lot boundaries  

• Name, organization, and contact information  

for the map overlay creator  

(Does it meet Quality Level 3 standards?)  

• Vertical Datum of elevation data (e.g., NAVD 88)  

• Location of the data archive or metadata file  

(must be available for independent verification  

through a publicly available website or metadata)  

• Aerial imagery that correctly represents the  

footprint of the building  

• Date the LiDAR was collected  

Your floodplain administrator or a mapping professional can help you develop the map for your  

application. For other requirements, please use the How to Request a Map Amendment Guide.  

|

DECEMBER 2018  

USING LIDAR FOR MAP AMENDMENTS  

2

CALCULATING ELEVATIONS USING LIDAR  

The lowest adjacent grade (LAG) for a building, or the lowest lot elevation (LLE) for a lot, will be compared  

to the effective Base Flood Elevation (BFE) to determine the flood zone. If LAG/LLE is at or above the BFE  

on the current flood map, FEMA can issue a removal determination. For buildings or lots that cannot be  

removed from the high-risk zone using LiDAR, certified elevation data will be required for a standard LOMA  

determination.  

Using LiDAR Contours  

For LOMA submittals that include LiDAR data contours, FEMA will subtract half the contour interval or  

1 foot, whichever is greater, from the lowest contour closest to (but not going through) the building (to  

determine the LAG) or the lot (to determine the LLE).  

CALCULATING THE LOWEST GRADE (LAG)  

1. Determine the closest contour lower than the building footprint.  

2. Subtract 1/2 the contour interval or 1 ft., whichever is greater to determine the applicable LAG or Lowest Lot Elevation (LLE).  

Elevation 802’  

This structure is Out as Shown (OAS)  

Requests where the FIRM data clearly  

LAG would be 797’  

(closest lower contour  

shows the property/structure to be Out as  

Shown are not eligible for LiDAR review.  

of 798’ - 1’)  

Elevation 800’  

LAG would be 797’  

(closest lower contour  

of 798’ - 1’)  

Elevation 798’  

LAG would be 795’  

(Will Need Field Survey) (closest  

lower contour of 796’ - 1’)  

Elevation 796’  

Zone AE  

Lake BFE = 796.2  

|

DECEMBER 2018  

USING LIDAR FOR MAP AMENDMENTS  

3

Using LiDAR Point Data  

For submittals that include LiDAR point data, FEMA will subtract 2 feet from the lowest point closest to the  

building (to determine the LAG) or the lowest point on the lot (to determine the LLE). Multiple points must  

cover the building/lot for this method.  

•365.53  

Zone AE  

Lake BFE = 360.0  

•369.09  

•369.05  

•369.31  

LAG would be 360.77’  

(lowest adjacent  

point -2')  

•362.85  

•366.38  

•367.99  

•369.49  

•371.34  

•370.68  

363.62•  

364.94•  

362.77•  

•371.8  

•373.18  

367.68•  

•374.35  

•374.58  

•374.56  

•374.58  

•371.57  

•372.24  

•370.11  

WHERE DO I GO IF I NEED HELP?  

To speak with a Map Specialist about the amendment process, contact the FEMA Map Information  

eXchange (FMIX) at 877-FEMA-MAP (877-336-2627) or FEMAMapSpecialist@riskmapcds.com  

|

DECEMBER 2018  

USING LIDAR FOR MAP AMENDMENTS  

4

Two agencies with three national programs converge within GIS...

Two agencies with three national programs converge within GIS and fill a void in risk mapping. USGS 1M DEM access on The National Map (TNM), USGS StreamStats, and FEMA National Flood Hazard Layer (NFHL). The GIS software used for development is QGIS (Quantum Geographic Information System). The process also supports a second FEMA effort known as Base Level Engineering (BLE).

A current GIS method and process built around the DOS program Quick2 as published by FEMA to compute water-surface elevations in open channels of all types. The Quick-2 Tutorial exposes the user to single-lot and multiple-lot case studies. The DOS program has been combined with DOSBox, a free and open-source emulator that runs software for MS-DOS compatible disk operating systems, primarily video games.

Quick2 requires inputs measured by standard GIS methods and discharge values that can be provided by StreamStats and Base Level Engineering resources. A spreadsheet is then used to collect measurements and values formatting a text file input for Quick2. Another national layer used is USGS Landcover that provides the bases for Manning's N values needed in the calculation.

ITS HERE!!! Project Download

The National Map, a collaborative effort led by the U.S. Geological Survey (USGS), plays a crucial role in providing topographic information for the United States.

StreamStats is a powerful web application that provides essential streamflow statistics and other hydrological information. 

The National Flood Hazard Layer (NFHL) is a geospatial database maintained by the Federal Emergency Management Agency (FEMA).

FEMA Base Level Engineering (BLE) is an automated riverine hydrologic and hydraulic modeling approach that builds on lessons learned to produce a base line understanding of a community’s flood risk.

National Flood Risk Managment - Historical Document

IMPROVING PUBLIC SAFETY –
FROM FEDERAL PROTECTION TO SHARED RISK REDUCTION
 Major General Don Riley
US Army Corps of Engineers

2/26/2008

Responsibility for flood risk management in the United States is a shared responsibility between multiple Federal, State, and local government agencies with a complex set of programs and authorities. Nationally, both the US Army Corps of Engineers (USACE) and the Federal Emergency Management Agency (FEMA) have programs to assist states and communities in reducing flood damages and promoting sound flood risk management. The authority to determine how land is used in floodplains and to enforce flood-wise requirements is entirely the responsibility of state and local government. Floodplain management choices made by state and local officials, in turn, impact the effectiveness of federal programs to mitigate flood risk and the performance of federal flood damage reduction infrastructure. One key challenge is to ensure that as the public and government leaders make flood risk management decisions, they integrate environmental, social, and economic factors and consider all available tools to improve public safety. Importantly, we must ensure the public is educated both as to the risks they face and actions they can take to reduce their risks. Because of this complex arrangement of responsibilities, only a life cycle, comprehensive and collaborative systems approach will enable communities to sustain an effective reduction of risks from flooding.

 Where we are now – “The government will protect us.”

Individual agency processes and procedures typically have provided the venue for planning and implementation of flood damage reduction measures. The present process to engage the Corps of Engineers is on a project-by-project basis, even though the Corps has made advances in incorporating collaborative approaches and assessing alternatives in a watershed context. Traditionally, the Corps focuses on reducing flood damages by managing floods that cause damage largely by decreasing the probability of flooding. The Corps develops alternatives based on reducing known potential flood damages, with minimal consideration of future land use or other social effects. Additionally, the Corps infrequently assesses options to reduce consequences should a failure occur. Whether communities strive for 1% level of protection or greater, the present process drives decisions based on reducing the potential for failure or reducing flood damages and does not incorporate an assessment of localized risks and consequences. Figure 1 is an example of the present paradigm – a system based on an appropriate “level of protection”, which provides credence to the notion that “the government is responsible” and “therefore, we are protected.” Complicating the matter, many prudent costs share sponsors seek to limit their costs, which drives some to seek to achieve only a level of protection whereby community members will not be required to purchase flood insurance.

Figure 1 – Selecting Level of Protection.

Where we need to be – “We are all responsible for our safety.”

To significantly improve public safety, we are pursuing a level of public education at which our fellow citizens are so well informed they are able to assume responsibility for decisions they make about where and how they want to live and work. We then can engage in a comprehensive and multi-government and private citizen collaborative process to managing flood risk to achieve levels of tolerable risk. The Corps is expanding our traditional approach to focus on the most effective combination of tools available that citizens may use to lower or “buy down” their flood risk (as illustrated in Figure 2). We will consider not only reducing the probability of flooding, but also reducing the consequences should a flood occur. A multitude of options and tools becomes more evident through the process of assessing the consequences of a flood. Furthermore, the decision on which tools to implement involves all stakeholders. For example, the Corps can help reduce risk by levee construction. Whereas in a coordinated but independent action, local government can further reduce flood risk by implementing flood plain management actions such as evacuation plans, zoning ordinances, and public outreach.

 This cannot be achieved without a new paradigm of joint partnerships in a comprehensive approach of public education and flood risk management. For instance, the insurance industry has a similar goal of assessing hazards and therefore, there exists an opportunity for the federal government and insurance industry to leverage mutual efforts, such as in the areas of research and development, implementation of assessment tools, and increase of public and policy-makers awareness. 

Figure 2 – Flood Risk Management: All Stakeholders Contribute to Reduce Risk.

What we are doing now

In May 2006, USACE established the National Flood Risk Management Program (NFRMP) to take the first step of bringing together other federal agencies, state and local governments and agencies, and the private sector to develop and implement a unified national flood risk management strategy that eliminates conflicts between different flood risk management programs and takes advantage of all opportunities for collaboration. Additionally, we are seeking partnerships with those that best understand risk, such as banking and insurance industries to share data and risk model development. We also wish to collaborate more closely with business councils and developers so they understand local flood risks and can assist us in public education campaigns.

 An integral part of the NFRMP is the Interagency Flood Risk Management Committee (IFRMC), with core leadership from USACE, FEMA, Association of State Flood Plain Managers (ASFPM), and the National Association of Flood and Stormwater Management Agencies (NAFSMA). This committee will be expanded to include other stakeholder groups, such as resource agencies. Through this process, organizational leadership should use or change, when practicable, existing policies and programs to transition into a comprehensive and shared process of lowering or “buying down” flood risks. As the transition occurs, the IFRMC should identify and recommend necessary administrative, policy, and legislative changes for complete implementation of the collaborative risk-informed decision process for managing flood risks.

Original Document

Quick2 FEMA Tutorials

Quick2 was developed during the Microsoft DOS operating system and the Managing Zone A - FEMA 265 manual came with Quick2 software on a 3.5 inch floppy disk (in 1995). In addition FEMA created other references that showcased GIS and digital flood insurance rate maps (DFIRM) using interactive tutorials.

The tutorials are in the obsolete SWF format but are still available on FEMA's website site.  Quick2 is no longer available from FEMA but is still listed as approved software. The SWF files do not automatically play unless you install a player or use an on-line player.

Found an SWF online player and thought I would share. It's simple: download the SWF files below, open the ruffle.rs/demo/ web site in your web browser and drop the file in the window.

ENJOY👍

Quick-2 Tutorial Overview

The Quick-2 Tutorial is a very detailed explanation of the processes published in FEMA 265. Very informative even today.

GIS Tutorial Series II

GIS Tutorial Series III

The tutorial series above reflects FEMA's efforts to integrate GIS into the mapping process and documents the conversion of FIRM maps to DFIRM maps.

Managing Floodplain Development in Approximate Zone A Areas

This is the main reference for the BFE process as it existed in 1995. This copy has been highlighted for convenience. 

CAUTION: None of the above references are comprehensive or current. They are out of date and do not leverage current GIS capabilities or mapping practices. They are intended as historical references only.

QUICK2 / QUICK2AF Ingredients List and BFE Recipe

REFERENCES

• MANAGING FLOODPLAIN DEVELOPMENT IN APPROXIMATE ZONE A AREAS 
• Guidance for Flood Risk Analysis and Mapping: Alluvial Fans
• REST Service to NFIP mapped Alluvial Fan Areas
• CAUTIONS: Backwater Conditions and Alluvial Fans

DOWNLOADS

• Quick2af (download)
• Quick2af BFE Worksheet (download)
• Statewide/County SFHA Database (download)
• Stateplane Zones (download)
• DEM for request area (State/USGS/NRCS)
• StreamStats stream grid (download)
• Landcover for request area (download)
• Landcover Mannings N reference (download)
• QGIS (if needed) (QGIS.ORG) (long-term release recommended)
• QGIS Plugins: Lat Lon Tools, Profile Tool and QuickMapServices (w/contribution pack)

CREATE AND MEASURE IN GIS

1. Create a BFE project in GIS and locate the project by coordinates
2. Use the state plane CRS of the project location in feet (Stateplane Zones)
3. DEM(s) is/are merged and converted to vertical feet if needed (DEM for request area)
4. One foot contours are created from DEM
5. Cross-section layer is created using H&H common practice and assigned the project CRS
6. Measurements are then taken from attached layers (using workbook working down and right through tabs).
7. Backwater test from nearest downstream Zone AE elevation (State SFHA Database).
8. Place a cross sections are placed from left to right looking downstream with a state plane projection in feet, one at home/site and one upstream a minimum 100 feet with a positive slope value and a change in elevation minimum of a foot.
9. StreamStats report is generated from Cross Section intersection with NSS stream grid (fill in basin sq mi, region, 1% AEP discharge).
10. Mannings N is determined from XS, aerial, landcover, and Mannings N reference. Stream is always 0.04.
11. Profile is created from 40 points at the downstream XS of location (copied) and pasted into the worksheet Downstream XS tab. Copy and past from resulting QGIS attribute table by creating SHP file, points along line spaced length divided by 39, and extract elevations from DEM.
12. Left and right banks are identified in Downstream XS tab Notes field
13. The Quick2 Worksheet tab fields: Number of Stations, Left Bank Station, and Right Bank Station - column A is text file input for Quick2.

FEMA Quick2 Workbook spreadsheet

The Quick2 program was programed before geographical information system (GIS) software and is  designed to calculate a Base Flood Elevation (BFE) by inputting:

• station and distance values
• a discharge value
• bank stations
• Manning's N values
• and a slope value

Once entered a water surface elevation is generated that can meet FEMA minimum BFE requirements. When reading FEMA 265 - the Zone A document for Quick2 - the mapping references are now all GIS processes. 

The attached BFE Worksheet provides a place to collect the information and values needed in this process. Once all the values above are entered into the Workbook, they are formatted into a Quick2 formatted file that is imported. Once imported, the slope is entered and a result screen is displayed. The result screen references a WS ELEV (water surface elevation) that is calculated from a referenced discharge.

The discharge is referenced from the USGS StreamStats program for the stream location. Depending on the state and USGS study an entire range of discharge values is available and can include the 1% annual chance discharge value. It is this value that can be used to calculate a FEMA BFE for Zone A's.

The value of this Worksheet is for the utility of collecting the individual variables and to format a text file for input into Quick2.

Download HERE