Effects of August 1995 and July 1997 Storms in the City of Charlotte and Mecklenburg County, North Carolina

Prepared in cooperation with the City of Charlotte and Mecklenburg County

RAINFALL IN THE CITY OF CHARLOTTE AND MECKLENBURG COUNTY DURING THE STORMS OF AUGUST 26-28, 1995, AND JULY 22-24, 1997

Total rainfall in Mecklenburg County ranged from 3.87 to 9.37 inches during the August 1995 storm (fig. 2). Highest rainfall amounts were concentrated in the southeastern part of Charlotte between Providence Road and East Independence Boulevard, primarily in the Little Sugar Creek and McAlpine Creek drainage basins (table 1). The recurrence interval for a 24-hour storm exceeded 100 years in this part of the city, but the recurrence interval was less than 5 years in much of the northwestern part of Charlotte (fig. 3).

Rainfall amounts during the July 1997 storm generally exceeded those of the August 1995 storm, with a maximum total rainfall of 13.11 inches recorded for the event (fig. 4). The maximum rainfall amount measured in a continuous 24-hour period during the July 1997 storm was 11.40 inches (table 2), which exceeds the 100-year storm total by 4.3 inches. The 24-hour rainfall recurrence interval exceeded 100 years for much of the central part of Mecklenburg County, including a large percentage of the Irwin Creek and Little Sugar Creek Basins (fig. 5, table 1).

In order to determine the distribution of rainfall recurrence intervals in Mecklenburg County, the USGS developed software to compute the maximum amount of rainfall recorded during specified periods for the durations listed in this fact sheet. The rainfall amounts for each of the durations are summarized in table 2. For example, the values listed for the 30-minute duration were obtained by identifying the largest rainfall amount that occurred during a consecutive 30-minute period at each of the raingages in the network. The maximum, then, represents the highest of these values for the network, and the minimum represents the lowest of these values.