1. INTRODUCTION

Everyday thousands of flood determinations are being completed on properties across the United States. Industry designed Geographic Information Systems (GIS) can automatically assess most property locations; however, there are properties that can only be processed through manual mapping analysis. These types of properties usually fall into one of four categories: new construction (newly parceled lots, new streets, new addresses), rural properties with non-standard addresses (rural route and box) or with addresses that cannot be geocoded accurately, manufactured homes that are placed at locations with unassigned addresses, and locations that are borderline to 100-year flood zones and must require accurate analysis of the property.

 

This paper will discuss the viability of using a global positioning system (GPS) for accurately determining the location of these properties for flood zone analysis. 

 

2. BACKGROUND

 

In 1968, the U. S. Congress created the National Flood Insurance Program (NFIP) with the passage of the National Flood Insurance Act. This program was designed to provide an insurance alternative to disaster assistance caused by floods. Property owners in participating communities can purchase insurance protection against losses from flooding. Communities become participants in the NFIP based on an agreement with the Federal Government that states if a community will adopt and enforce a floodplain management ordinance to reduce future flood risks to new construction in Special Flood Hazard Areas, the Federal Government will make flood insurance available within the community as a financial protection against flood losses. In support of the NFIP, the Federal Emergency Management Agency (FEMA) produced Flood Hazard Boundary Maps (FHBMs), Flood Insurance Rate Maps (FIRMs), and Flood Boundary and Floodway Maps (FBFMs). These maps were developed with the help of the Army Corp of Engineers using topographic maps, field surveys, and historical flood data.

Congress expanded the scope of the NFIP when it passed the National Flood Insurance Reform Act of 1994. In this legislation, a process was put in place for identifying properties located in high-risk 100-year flood plains and requiring insurance for those properties. It also established rules for new construction in 100-year flood zones. The summary of the process and rules was that any time Federally regulated lending institutions made loans (new homes or businesses, refinances, etc.), a flood determination must be completed for that property and any structure(s) on property. It also established that flood determinations must be completed by a guaranteed flood zone determination company. Prior to this law, flood zone determinations could be completed appraisers, surveyors, or just about any who had flood maps for the location.

 

 

3. METHOD

 

Most determination companies use an industry designed GIS for completing flood zone requests. The systems combine a base street map layer with a layer of the digitized flood zone maps. This enables the system to complete automated flood zone determinations for properties by geocoding an entered address and providing the flood zone information from the flood map layer. Many properties, however, may not get automated “hits” because the system simply cannot geocode the submitted address. The address could be a new property location (new construction or newly parceled land), a rural property with a non-standard address (rural route and box), or a property with addresses that cannot be geocoded accurately.

Currently, these property locations have to be mapped out manually using additional mapping resources such as, updated local and regional book and paper maps, legal descriptions, subdivision plats, and tax parcel maps. Most of these resources are not free; in fact, they can be very expensive and hard to obtain. This combination of time, money, and labor can hinder a flood zone determination company’s ability to be profitable.

 

A solution to this problem could come from the use of Global Positioning System (GPS) receivers. A latitude/longitude coordinate for a property could provide supplemental location data to the traditional property address. Great! How will the determination companies obtain this additional data?

Anytime a property is being sold, an appraisal report must be performed. If a licensed appraiser had a GPS receiver when the site inspection was done, this person could simply mark a waypoint at the front door of the home. The latitude/longitude along with the metadata such as, the date and type of GPS receiver used, could be recorded as part of the report. These reports are included in the loan documents, which could be forwarded to the determination company at the time of the flood determination request. This additional information becomes very useful when manual mapping is necessary for completing flood zone analysis. The mapper can simply enter the latitude/longitude into a geocoding program and find the property site instantly.

 

 

 

 

4. DATA AQUISTION

 

To demonstrate the process I described, I used a Garmin 12xl GPS receiver and marked waypoints at three locations. One location was my house, which was built in 1998.The other two locations are new homes that are currently under construction in a new subdivision. The streets in that subdivision were completed just last January (2000); thus, they will not appear on any mapping programs or maps at this time. The street my home is on can be found on updated maps of the area, but still hasn’t been digitized into mapping programs.

 

            After marking the waypoints with the receiver, I recorded the latitude and longitude, date and time, location description (property address), and GPS receiver used. This information was made as a data table in Excel ‘97. I then took this information for use on three separate geocoding systems.

 

 The first was the Delorme Street Atlas USA 7.0. This system can download and import latitude/longitude coordinates and display the locations with marker icons. It also has a standard input window, which I used for my properties. This system also accepts the latitude/longitude coordinates in degrees/minutes/seconds or decimal form.

 

The second system I used was the Microsoft Streets 2000 program. This system can also import the coordinates; however, the input window requires the latitude/longitude to be in decimal form.

 

The third system I used is an industry designed GIS system called Geolocator. It has the base street map information with a digitized flood zone layer. This system proved more difficult, however, because it does not have latitude/longitude entry fields. It requires the user to get to the regional area (zip code) first, and then a latitude/longitude input window can be accessed. The advantage this system provides is that once the coordinates are marked, flood data is instantly available.

 

 

5. GPS WAYPOINTS AND GEOCODING RESULTS

 

Excel Table:

 

Waypoint ID	Location Description	Waypoint Description	year built	Latitude	Longitude	Date	GPS Receiver
1	1534 Cushendall Dr, Roseville, CA 95747	single-story home	1998	N38 45.573'	W121 20.559'	05/01/2000	GARMIN 12XL
2	1618 Buckwood Dr, Roseville, CA 95747	two-story home	2000	N38 45.599'	W121 20.261'	05/02/2000	GARMIN 12XL
3	1603 Etchingham Dr, Roseville, CA 95747	single-story home	2000	N38 45.505'	W121 20.176'	05/02/2000	GARMIN 12XL

 

            Delorme 7.0:

 

As you can see on the above map, the streets are not yet digitized at the latitude/longitude for these locations.

 

 

 

 

Microsoft Streets 2000:

 

Again the streets are too new to be shown.

 

 

 

 

 

 

 

Geolocator:

 

The Geolocator map above provides instant flood zone data at the latitude/longitude coordinates.

 

 

6. CONCLUSION

 

Is there a viable of use for GPS in completing flood zone determinations of properties?

For flood determination companies, the ability to acquire latitude/longitude coordinates for property locations could be a very valuable resource. Most company’s automated systems run between 50 to 70 percent “hit” ratio on the total volume of requests. That means 30 to 50 percent of the properties must be manually mapped. If an industry designed GIS system could be programmed for latitude/longitude input, a majority of these determinations could also get automated “hits”. This would leave only a small percentage of properties to be manually mapped, saving time and money in extra resources and labor.

 

How accurate are latitude/longitude coordinates when a waypoint is marked on a GPS receiver?

On May 1, 2000, President Clinton announced that the United States would stop the Selective Availability (SA) transmission that limited the accuracy of civilian use GPS. Before this action, the Garmin 12xl accuracy was + or – 100 meters. After SA was turned off, the unit’s accuracy improved 10-fold to + or – 10 meters. The following diagrams illustrate this:

 

Before:

 

 

After:

 

 

 

 

 

7. REFERENCES

 

The Federal Emergency Management Agency’s (FEMA) National Flood Insurance Program (NFIP) web site, “Introduction to the NFIP”, http://www.fema.gov/nfip/intnfip.htm

 

The Garmin web site, “Decision To Discontinue SA Announced, GPS Position Accuracy Increased”, http://www.garmin.com/whatsNew/announcements2000/announcements01.html

 

 

8. DATA SOURCES

 

Garmin 12xl GPS receiver

 

Delorme Street Atlas USA 7.0

 

Microsoft Streets 2000

 

Geolocator, Geologix Co., Placerville, CA

 

America’s Flood, Inc., Rancho Cordova, CA