STORMWATER EVENTS

On September 17, 2004, Hurricane Ivan deposited an average of 6.25 inches of rain in a 24 hour period over the already saturated clay soils of the 277 square mile Chartiers Watershed. On that date, Chartiers Creek crested around 11:00 pm at 23.98 feet, topping the banks in many low-lying communities.  Peak flow was 23,.500 cubic feet per second, or 175,000 gallons per second, greater than the combined flow over the American & Bridal Falls at Niagara Falls, which is 150,000 gallons per second.  The US Geological Survey (USGS) gauge at Carnegie monitored the flow, below:

USGS Gauge 03085500 at Carnegie
Graph of hurricane Ivan relative to year, detailed event and history

The graph above illustrates how Ivan relates to the normal flow of the creek.  In the course of nearly a year, Ivan and the January floods show as a sharp spike in the discharge rate while the overall discharge during the same period is also elevated relative to the norm.  A detailed weekly chart of stream depth also illustrates how rapidly the creek level rose during Ivan.  The history of records that have been kept since 1916 shows that the discharge rate during Ivan was twice that of previous floods.

  


WOODED SLOPES & NATURAL FLOODPLAIN

Allegheny Land Trust's flooded Wingfield Pines floodplain

Chartiers Creek meanders down the Crafton-Thornburg floodplain

Vegetation is especially important along the creek, where it filters pollutants coming into the water and slows the raging current.   Trees such as river birch, box elder and aspen stabilize creek banks naturally and are designed to re-grow from the roots after flood events. Strong trees like sycamore will not uproot easily and create shade for fish and form vital habitat and nesting sites for wetland birds such as the Great Blue Heron that depend on the fish in the creek for food. 

former golf course in Thornburg preserved as natural floodplain by municipality receives floodwaters
Mickey Bannon & Sue Primm rescue 29 fish from flooded CIT ballfields on Crafton floodplain
sand bars shows ripples from recently subsided water on the flood control levee in Crafton

Twenty nine stranded carp were rescued from Crafton's natural floodplain, above.

Natural floodplains recover quickly from flood events, leaving a layer of silt or mud as the only evidence, after the water gradually subsides.  

While flooded, wetlands birds such as geese, duck and heron enjoy the additional habitat, feeding on stranded fish and floating on the temporary ponds.  

flooded Chartiers Creek floodplain in Crafton watershed environmentalist John Hamm walks on silt deposited on flood control levee

  


FLOOD PHOTOS

Hurricane Ivan, along with the recent landslide in Killbuck Township, have highlighted the imperative need to incorporate best management practices into development.  

Municipalities and regulatory agencies can no longer afford to ignore development practices that put our quality of life at risk, in the name of economic incentive.  It has been clearly shown that far from economic health, ignoring best management practices invites economic disaster.  

Municipalities and regulatory agencies need to implement steep slope ordinances and adequate stormwater management plans and work with developers to insure understanding and compliance.  

Land use that incorporates green strategies and recognizes the value of the natural environment, particularly on steep slopes and floodplains, will curtail or forestall economic disaster.

Clicking on the links at left chronicle the height of Ivan's floodwaters and the aftermath.  Destruction of developed areas clearly shows the need for the mitigating effects of natural floodplains with native vegetation and riparian zones.  

Bridges trapped debris, backing up water to the point where it spills over and floods our communities.  

Land left in its natural state, especially on steep slopes and floodplains, prevents stormwaters from destroying our low lying communities by capturing excess water and sediment.  The economic value in the beauty of nature is an asset the residents of the Chartiers Watershed need to recognize, preserve and enhance.