Impacts of the May 2008 Storms

The Chesapeake Bay region received a one-two punch of powerful storms between May 9 – 12, 2008. The two unnamed spring storms were responsible for flooding in much of the Bay watershed, with central Maryland being particularly hard hit. Along with the downed trees and damaged properties, the storms also impacted water quality in the area's streams, creeks, and rivers.

The rains were responsible for dumping over 4 inches of rain throughout most of Maryland. Counties surrounding Washington, DC recorded over 8 inches. Watershed-wide radar estimates of rainfall can be observed in Figure 1.

Figure 1. Area Precipitation Totals

Map displaying high levels of precipitation in Maryland.

Source: www.intellicast.com

The region had previously been in the midst of a nearly year-long dry spell, but with the heavy precipitation this spring, the drought may be over. While the rains will have long term benefits such as recharging groundwater levels, in the short-term, they were responsible for carrying large amount of sediments and nutrients into the Bay. Looking at the network of real-time Continuous Monitoring sites in Maryland's portion of the Bay, clearly shows the immediate effects of the storms on Bay water quality. Continuous monitoring data, available on the Eyes on the Bay website, recorded many interesting impacts throughout the Bay (Figure 2).

Data from the upper Bay show a short spike in turbidity levels. Turbidity is a measure of water clarity - higher turbidity indicates less clear water. Turbidity levels rise when sediment and other suspended material enter the water body during rain storms. Other factors, such as algae blooms, may also negatively impact turbidity levels. Poor water clarity prevents underwater grasses and other aquatic resources from thriving. The timing of this rain event corresponds to the early part of the SAV growing season (April – October) when plants require more light to reach the bottom sediments. DNR will continue to assess SAV beds to determine the impacts of these high rain events and subsequent turbidity spikes on SAV abundance throughout the summer.

The mid-Bay stations also show a strong turbidity increases, but these are accompanied by a dip in salinity, as a result of the fresh water input.

The monitoring stations on the Potomac River indicate two pulses of run-off, as that area received the worst of both storms, on May 9 and again on May 11–12.

Figure 2.

Upper Bay
Susquehanna River,
Havre de Grace
Susquehana River turbidity. Peak on May 12.
Susquehana salinity. No major trends.
Elk River,
Locust Point Marina
Elk river turbidity. Peak on May 12.
Elk river salinity. High fluctuation.
Mid Bay
Chesapeake Bay,
Sandy Point
Sandy point turbidity. Peak on May 12.
Sandy point salinity. Slight trough on May 12.
Corsica River,
Sycamore Point
Corsica River turbidity. Exptended Peak from May 12-14.
Corsica river salinity. Large trough from May 13-14.
Potomac River
Upper Tidal Potomac,
Fenwick Shores
Upper potomac turbidity. Peak from May 12-13.
Upper potomac salinity. Several troughs May 9-12.
Middle Tidal Potomac,
Swan Point		 Middle Potomac turbidity. Peaks on May 10 and 13. Middle Potomac salinity. Downward trend through May.

What can I do to lessen impacts on the Bay?

Storm events of this magnitude provide another reminder of the impact that impervious surfaces such as roads, rooftops and parking lots have on the natural landscape. There are many things you can do to help improve the health of the Chesapeake Bay and its tributaries:

  • Plant trees along streamside property. Tree roots will slow erosion and absorb the flow of nutrient runoff.
  • Dispose of household chemicals properly. Toxic chemicals poured down the drain could end up in the rivers.
  • Pump out septic tanks regularly (every 3-5 years). A failing system can contaminate groundwater.
  • Use fertilizer sparingly. If you must fertilize, try doing it in autumn, when it will have less of an impact on the rivers.
  • Conserve water. Use rainwater for plants, take shorter showers, and turn off the faucet when brushing your teeth.
  • Support land protection initiatives. Preserving existing green space is much easier than restoring degraded areas.
  • Drain gutter spouts into rain barrels or grassy areas. This will reduce erosion, which adds sediment to the river.
  • Get involved. Let state, county, and local officials know that water quality is important to you.
  • Carpool, or try biking or walking. Exhaust fumes contain nitrogen oxides, which can end up in the river and bay.

Sources of information: