Soon, a forecasting system for predicting flash floods in advance

Washington, July 23 : Communities living near vulnerable creeks and rivers may soon get advance notice of potentially deadly floods, thanks to the development of a new forecasting system.

Being tested this summer by the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, the system is known as the NCAR Front Range Flash Flood Prediction System.

It combines detailed atmospheric conditions with information about stream flows to predict floods along specific streams and catchments.

"The goal is to provide improved guidance about the likelihood of a flash flood event many minutes out to an hour or two before the waters start rising," said NCAR scientist David Gochis, one of the developers of the new forecasting system.

"We want to increase the lead time of a forecast, while decreasing the uncertainty about whether a flood will occur," he added.

The Front Range, because of its steep topography and intense summer storms, is unusually vulnerable to summertime flash floods.

Such floods have claimed the lives of hundreds of people and accounted for hundreds of millions of dollars in damages throughout the region's history.

Flash floods are difficult to predict because they happen suddenly, often the result of heavy cloudbursts that may stall over a particular watershed.

Forecasters can give a few hours' notice that weather conditions might lead to flooding, and radars can detect heavy rain within minutes.

But whether a flood hits a specific river or creek also depends on soil, topographic, and hydrologic conditions that are characteristic to particular watersheds.

Thus, emergency managers may not know that a flash flood is imminent until the waters begin to rise.

The goal of the NCAR system is to provide officials at least 30 minutes warning of flash flooding in specific watersheds, and possibly as much as an hour or two.

It is designed to pinpoint whether a particular stream is likely to overflow, as well as forecast the likelihood of flash floods producing events across a larger region.

The system integrates the weather information with datasets about hydrology and terrain.

These datasets incorporate information about land surface conditions, such as terrain slope, soil composition and surface vegetation. They also include information on stream flow and channel conditions.

By combining information about the land and the atmosphere, the system can project whether an intense storm is likely to stall over a specific area of the Front Range and how that may impact the flow of water on the ground.

According to NCAR scientist David Yates, "This new system is unique in that it provides a detailed forecast of the location and duration of a severe storm, as well as the watershed's likely response to the heavy rain."

ANI