U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3029

May 2010 Printed on recycled paper

Overview

The Real Time Flood Alert System is a web-based 

computer program, developed as a data integration 

tool, and designed to increase the ability of emergency 

managers to rapidly and accurately predict flooding 

conditions of streams in Puerto Rico (fig. 1). The system 

includes software and a relational database to determine 

the spatial and temporal distribution of rainfall, water 

levels in streams and reservoirs, and associated storms 

to determine hazardous and potential flood conditions. 

The computer program was developed as part of a 

cooperative agreement between the U.S. Geological 

Survey Caribbean Water Science Center and the Puerto 

Rico Emergency Management Agency, and integrates 

information collected and processed by these two 

agencies and the National Weather Service. 

Introduction

 Floods are the most destructive and costly of all 

natural disasters in the United States, in terms of loss 

of life, and damage and destruction of property and 

infrastructure. The average cost of restoring property 

and infrastructure, between 1903 and 2007, was 

estimated at $5.24 billion annually. Damage to property 

and infrastructure was lowest in 1906, with only $34 

million in associated costs, and was highest in 2005, 

due to Hurricane Katrina, with $125 billion (costs are 

normalized to 2007 dollars). The loss of life due to 

floods varies greatly between years, and has ranged 

from 0 to 554 casualties per year since the early 1900s 

(National Oceanic and Atmospheric Administration, 

2009). Death statistics do not include those caused by 

Hurricane Katrina during the months of August and 

September 2005. Most of the flood-related deaths are 

caused by flash flooding. 

Real Time Flood Alert System (RTFAS) for Puerto Rico

Prepared in cooperation with the Puerto Rico Emergency Management Agency (PREMA)

Figure 1.  Real Time Flood Alert System Home page.

Printed on recycled paper
data at specific high frequencies. The rainfall 

stations’ information is accessed by way of radio 

signal receiving equipment located at a base station. 

In addition, the USGS has a precipitation network 

that includes 132 rainfall stations that collect quasicontinuous data. The streamflow monitoring network 

is also operated and maintained by the USGS, and 

consists of approximately 190 automated stream 

gage-height and reservoir water-level stations. Gage 

height is converted to streamflow discharge using 

rating curves developed for each stream. The NWS 

Doppler radar is another source of information that 

complements the rainfall station, and gage height 

data obtained by the two hydrologic networks. The 

Doppler radar provides color coded images that 

display spatial information on instantaneous and 

cumulative rainfall throughout Puerto Rico, the 

United States, and the British Virgin Islands. The 

USGS stations are equipped with data collection 

platforms that transmit data, either on a self-timed 

or random reporting basis through the Geostationary 

Operational Environmental Satellite (GOES) to the 

USGS Caribbean Water Science Center. During 

normal operation, the stations transmit hourly data 

at 15-minute interval. During storm conditions, 

however, the station enters in an alert mode and begins 

transmitting data every 5 minutes if a sensor detects a 

sudden rise in the stream or reservoir stage-level, or a 

rapid rate of accumulation of precipitation.

Several agencies can provide access and 

interact during extreme events to facilitate data and 

information useful during hydrologic emergencies. 

This array allows the National Weather Service, River 

Forecast Center to use the USGS data to run flood 

prediction models.

In Puerto Rico, floods can be extremely 

destructive because of the island’s steep, 

mountainous topography and relative proximity to 

dense population centers (fig 2). For example, in 

October 1985, the rainfall in Puerto Rico associated 

with a nearly stationary tropical depression caused 

170 deaths, and damaged or destroyed about 3,000 

homes (U.S. Geological Survey, 1989). Most of the 

island’s major river systems have their headwaters 

in the central mountain range where rainfall 

during tropical storms and hurricanes is typically 

prolonged and intense. The stream valleys are 

narrow, relatively short in length, and steep—ideal 

conditions for the generation of flash flooding. 

Approximately, one-third of the population on the 

island lives in flood prone areas and the consequent 

potential for property damage and loss of life is 

very high.

In order to enhance the ability of emergency 

managers to rapidly and accurately anticipate 

floods, thereby increasing the lead-time available to 

handle the emergency, the U.S. Geological Survey 

Caribbean Water Science Center (USGS-CWSC) 

developed the Real-Time Flood Alert System 

(RTFAS) computer program. The objective of this 

program is to reduce the time needed to assess 

rainfall rates, the status of stage and discharge 

in rivers, and sudden changes to reservoir stage 

caused by an increase in upgradient streamflow. 

RTFAS was developed as part of a cooperative 

agreement between the USGS and the Puerto Rico 

Emergency Management Agency (PREMA), and 

integrates information collected and processed by 

both agencies and the National Weather Service 

(NWS). 

Data Sources: Precipitation and Streamflow 

Networks, and Doppler Radar

Although hydrologic networks may not be 

available for each geographic region in the United 

States, access to continuous or near real-time data 

from these networks is possible by contacting 

a local USGS Science Center. Available nearreal-time data used for early detection of extreme 

hydrologic events are: 

1. Precipitation and meteorological stations

2. Streamflow gaging stations

3. Doppler radar

In Puerto Rico, some of the precipitation 

stations are operated by PREMA. This precipitation 

network is a cooperative flood warning system, 

called the Automated Local Evaluation in Real 

Time (ALERT). The ALERT system consists of 

nearly 50 automated rainfall stations transmitting 

Figure 2.  Aerial view of the topography of Puerto Rico.

Caribbean Sea

Image from ©2010 Google, Data SIO, NOAA, U.S. Navy, NGA, GEBCO. 

Image U.S. Geological Survey, ©2010 Europa Technologies

Location Map
Figure 3.  U.S. Geological Survey (USGS) and Puerto Rico Emergency Management Agency (PREMA) precipitation networks.

RTFAS User Environment

RTFAS was developed using Adobe FlexTM, which 

generates web-based applications that are executed in 

the Adobe Flash Player; thus, the Adobe Flash Player 

plug-in is required. Adobe FlexTM generates Rich 

Internet Applications that allow real-time interactivity 

that is impossible to accomplish in standard Hypertext 

Markup Language (HTML) alone. The emergency 

managers can access RTFAS using any of the following 

browsers: Microsoft Internet Explorer®, Mozilla 

Firefox®, Apple Safari®, and Google Chrome®.

Interface Overview

The RTFAS interface consists of four tabs: Home, 

All Stations, Bulletins, and Forecasts, through which 

the user can access information that is collected and 

processed by PREMA, USGS, and the NWS. Once the 

interface is loaded, by accessing http://rtfas.er.usgs.gov, 

the Home tab is displayed. 

Description of Interface Tabs

HOME—includes general information and shortcut 

links. 

ALL STATIONS—can display spatial information from 

the PREMA precipitation network, the USGS hydrologic 

network, and the NWS Doppler radar images. 

Figure 4.  Example of monitored stations inside and outside the

PREMA operational zone (Fajardo, zone #11).

The display shows a map of Puerto Rico with the location 

of the PREMA and the USGS precipitation stations (fig. 3). 

Stations are graphed with an inverted drop symbol, which is 

also used to represent the amount of rainfall accumulation 

using a color coded legend listed at the right edge of the map. 

Rainfall accumulation varies when the selected time interval 

is changed. The RTFAS interface allows the user to select the 

time interval by choosing from the available options 

(1, 3, 6, 12, 24 hours, 3, 7 days). The 1-hour rainfall radar 
Figure 5.  Gage-height (stage) at USGS surface-water stations and NWS Doppler radar

image with 45% opacity.

Figure 6.  Active text products from the National Weather Service.

image allows the user to prioritize the areas where 

rainfall intensity may be greatest.

When a station is selected with a click of the 

mouse, the program displays the chart and tabular data 

for individual sensor measurements during the last 

24 hours, historical peak elevations, and if available, 

flood impact summaries caused by specific gage 

heights. This provides a quick overview of the data 

associated with each station. Station data, if selected, 

are automatically updated every 3 minutes in the 

charts and tables.

In Puerto Rico, PREMA is divided in 

11 operational zones. Therefore, RTFAS 

allows each emergency manager to easily 

monitor their zone, allowing the list of 

stations to be filtered by zone. When a 

PREMA zone is selected, the zone and the 

hydrologic basins are delineated on the 

map and the stations within the hydrologic 

basins are displayed. Displaying all this 

information enhances the understanding 

of the relation between the measured 

parameters in the delineated hydrologic 

basin, even if the stations are located 

outside of the PREMA zone. It is important 

for the emergency manager to monitor all 

stations included within the boundaries of 

the hydrologic basin that contributes to the 

zone of operation assigned by PREMA 

(fig. 4). 

Streams are also displayed using a color-coded squared 

shape symbol (fig. 5) to determine the condition of the 

stream during an ongoing flooding event. Squares are 

colored ranging from ”No Flooding” to ”Major Flood” 

status, where a predetermined flood stage is indicative of 

the condition of the stream. Predetermined flood stage 

elevations are developed by NOAA to indicate flood status.

When the change in gage-height exceeds more than 6 

inches for the preceding 15 minutes, the station’s square icon 

will change to an up arrow (Õ), indicating that the level is 

increasing rapidly. A rapid 

decrease in gage-height is 

also important, and will be 

represented as a down arrow 

(Ô). These arrows serve as 

a visual cue indicating the 

potential for stream stage 

peak or recession status. 

In addition, stage and 

rainfall data can be viewed 

and toggled in both map and 

tabular formats. If a station 

is selected on one format, for 

example, by clicking on the 

Map marker corresponding 

to the station, RTFAS will 

synchronize the available 

information in the tabular 

format; therefore, the user 

will not have to scroll for the 

station on the table. 
BULLETINS—includes NWS text products: warnings, 

watches, area forecasts, and other related information 

(fig. 6). Products are grouped into three categories: 

informative, tropical and hazardous. The Bulletins tab also 

displays the products that remain active, shown in red. This 

feature eliminates products that are no longer active, thereby 

increasing the lead time available to examine imminent 

floods. The text product list is updated automatically by 

RTFAS every hour.

FORECASTS—consists of area forecast reports or weather 

summaries from the NWS (fig. 7). This tab provides a 

general indication of the weather conditions in Puerto Rico, 

and can provide information on future weather conditions. 

RTFAS updates the forecast information automatically every 

3 hours. 

Data Flow

 

The flow of data consists of three redundant data 

transmission systems (fig. 8). Although some of the 

information is generated onsite, data transmission is 

conducted and rerouted using three different transmission 

mediums: radio signals, the Internet, and satellite. Other 

relevant information, such as Doppler radar images and 

forecast products, are also used. This multi-system 

configuration ensures that timely information is available to 

be accessed by RTFAS, and in most cases, in near real-time 

without missing values or service interruptions.

The flowchart shown in figure 8 can be easily followed 

by looking at the different arrow colors. Each color—

orange, green, and blue—represents a different source of 

The USGS streamflow monitoring network transmits 

gage-height data from streams throughout Puerto Rico. 

Gage-height data are converted into streamflow discharge 

using rating curves developed for each stream, and are made 

available to RTFAS through the NWIS database. In addition, 

RTFAS has access to rainfall stations maintained and 

operated by the USGS. 

Finally, the NWS provides text products including area 

forecast discussions, and bulletins that are also incorporated 

into RTFAS. These can be downloaded from the NWS 

web servers, but are also available through the Emergency 

Managers Weather Information Network (EMWIN).

 In addition to the text products, the NWS Doppler 

radar data are made available through the NWS web servers. 

RTFAS downloads the accumulated 1-hour rainfall Doppler 

radar data at 15-minute intervals.

Summary

RTFAS is a web-based computer interface developed 

as a data integration tool, and designed to increase the 

ability of emergency managers to rapidly and accurately 

predict flooding conditions of streams. The hydrologic and 

meteorological data are provided by PREMA, USGS, and 

the NWS. The interface consists of several tabs through 

which the user can quickly access information collected 

and processed by the aforementioned agencies. RTFAS was 

developed using Adobe FlexTM, which generates web-based 

applications that execute in Adobe Flash Player, making 

it widely available on many computer platforms and web 

browsers.

Figure 7.  Real Time Flood Alert System (RTFAS), automatic compilation of 5-day

(extended) weather summaries from the National Weather Service (NWS).

information. It is important to indicate that 

RTFAS centralizes data compilations and 

facilitates access and information to and by 

users. Some of the information relevant during 

storms and extreme hydrologic events include: 

near real time streamflow discharge, rainfall 

accumulations, Doppler radar images, and the 

NOAA area forecast discussions. 

Among the different sources of information 

used by RTFAS are: (1) Puerto Rico Emergency 

Management Agency VHF (very high 

frequency) radio stations—coded with the 

orange arrow, (2) USGS field data stations—

coded with the green arrows, and (3) National 

Oceanic and Atmospheric Administration 

Doppler radar images and text products—coded 

with the blue arrows. 

PREMAs VHF transmissions include 

information from the PREMA stations to the 

RTFAS server. The field stations transmit a VHF 

signal that is sent to the USGS National Water 

Information System (NWIS) server, which in 

turn is forwarded to RTFAS server.
References Cited

Hydrologic Information Center National Weather Service, March 

19, 2009, Flood Losses: Compilation of Flood Loss Statistics, 

National Weather Service, accessed April 5, 2010, at http://

www.nws.noaa.gov/oh/hic/flood_stats/Flood_loss_time_series.

shtml.

U.S. Geological Survey, 1989, Puerto Rico Floods and Droughts, 

National Water Summary 1988-89, United States Geological 

Survey Water Supply Paper 2375, p. 475.

The information is available in the publication

“Real Time Flood Alert System (RTFAS) for Puerto Rico”

at http://pubs.usgs.gov/of/2010/3029/

U.S. Department of the Interior

KEN SALAZAR, SECRETARY

U.S. Geological Survey

Marcia McNutt, Director

Dianne López-Trujillo

U.S. Geological Survey

GSA Center, bldg 651 Federal Drive, Suite 400-15

Guaynabo, P.R. 00965-5703

(787) 749-4346 ext. 257

dlopez@usgs.gov

Question related to this software can be directed to the author:

Figure 8.  Real Time Flood Alert System (RTFAS) data flow chart.