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Floyd’s Effects on Maryland and Delaware Waters
Released: 9/22/1999

Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192
Gary Fisher 1-click interview
Phone: 410-238-4259 | FAX: 410-238-4210




Now that the fallen trees have been removed, most power is restored, and the floods have started to recede, U.S. Geological Survey (USGS) personnel have come in from the outdoors to dry off and start working on the streamflow and water-quality data they have been collecting since last Thursday, when Hurricane Floyd came through the area.

Precipitation totals varied widely between Garrett County and the Atlantic coast of the Delmarva Peninsula. Streamflows have been reflecting that variation, with only slight rises in western Maryland (where relatively little Floyd-related rain fell) and 500-year floods in some streams on the Delmarva (where there were many inches of rain). Several USGS stream gaging sites were damaged by flooding and are being repaired as quickly as possible. Peak flood stages after Floyd and previous record-high flood peaks are listed below for some sites.

Floyd’s effect on the ground water

Hurricane Floyd had an immedate effect on ground-water levels in many parts of the area. Thirteen observation wells were measured in Maryland and Delaware just before and soon after Hurricane Floyd brought the rain. Water levels in 12 of the 13 wells rose as a result of the rain. In 8 of the wells, the water table is now in or above the normal range of water levels for this time of year. All the wells with water levels still below the normal range are west of the Chesapeake Bay.

The observation wells in Delaware and the Eastern Shore of Maryland are all within the normal range or above it. This is because the surficial aquifer on the Delmarva Peninsula is very sandy and permeable, so that a lot of the rain soaked in and reached the water table relatively fast. USGS scientists are continuing to monitor water levels.

Water and other data related to Hurricane Floyd in Maryland and Delaware may be found on the web at http://md.water.usgs.gov/. Other USGS hurricane information is at http://www.usgs.gov/hurricanes/.

As the nation’s largest water, earth and biological science, and civilian mapping agency, the USGS works in cooperation with more than 2,000 organizations across the country to provide reliable, impartial scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to the sound conservation and the economic and physical development of the nation’s natural resources, and enhance the quality of life by monitoring water, biological, energy, and mineral resources.

PEAK STREAM FLOWS AFTER HURRICANE FLOYD--Maryland and Delaware

NOTE: Floyd data are provisional and subject to revision

[Stage is in feet above datum; cfs is cubic feet per second; Mgal/day is million gallons per day; EDT is Eastern Daylight Time; n.c. is "not yet computed," i.e., analysis is in progress.]

Station
Number
Station
Name
Previous peak
flow of record
Hurricane Floyd--flood peaks Recurrence
interval*
Stage Flow
(cfs)
Flow
(Mgal/
day)
Date and time
(EDT)
01478000 Christina River at Coochs Bridge, Del. 5,530 (1989) 13.92 n.c. n.c. 9/16 4:30 p.m. 500
01478650 White Clay Creek at Newark, Del. 7,540 (1996) 17.13 n.c. n.c. 9/16 n.c. 500
01479000 White Clay Creek near Newark, Del. 11,600 (1989) 17.57 15,900 10,270 9/16 10:00 p.m. 500
01480000 Red Clay Creek at Wooddale, Del. 5,010 (1975) 13.93 n.c. n.c. 9/16 n.c. >100
01481500 Brandywine Creek at Wilmington, Del. 29,000 (1972) 15.43 28,700 18,550 9/16 n.c. 100
01483200 Blackbird Creek at Blackbird, Del. 712 (1972) 6.47 n.c. n.c. 9/16 5:15 p.m. 40
01491000 Choptank River near Greensboro, Md. 6,970 (1967) 13.92 6,420 4,150 9/17 5:00 a.m. 40
01493000 Unicorn Branch near Millington, Md. 1,160 (1996) 9.40 n.c. n.c. 9/16 7:30 p.m. 500
01493500 Morgan Creek near Kennedyville, Md. 7,500 (1972) 15.03 n.c. n.c. 9/16 n.c. 500
01495000 Big Elk Creek at Elk Mills, Md. 10,600 (1937) 14.53 9,780 6,320 9/16 5:30 p.m. 30

* "Recurrence interval" is a term used to simplify flood definition, and refers to the statistical chance that a flood of that magnitude will occur. For example, a "100-year flood" has a 1-percent (1 in 100) chance of occurring in any year; a "5-year flood" has a 20 percent (1 in 5) chance of occurring in any year, and so on. These events are assumed to be statistically independent of each other, so each year begins with the same 1-percent chance that a 100-year flood event will occur.


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