Flood Photos

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.

wake of the flood | natural floodplains | development | infrastructure 

IN THE WAKE OF THE FLOOD

Chartiers Flood Control Authority convened a meeting at the Collier Municipal Building  Tuesday, March 1st at 7:30pm to inform the public on their plans to dredge the Chartiers Creek channel and clear-cut along the banks in answer to citizen response to the flooding of last September.   It is the general opinion of the environmental community that clear-cutting the banks will only make the runoff worse and cause greater flooding problems.

The original flood control project was designed to send as much water down the creek as quickly as possible.  This works to control the seasonal flooding in a normal rainfall year.  However, in years of higher rainfall, such as we are experiencing now, it causes too much water to flow down the creek all at once, causing a peak flow that exceeds the creek's capacity and overflows the banks.  What is needed is to slow the water down, not speed it up.

A design of 50 years ago when most of the surrounding land was rural does not address the more urban land use of today, where shopping malls, parking lots and housing developments have created impermeable surfaces that do not soak up the rainwater.  The rain has to go somewhere, so it runs off down the slopes and adds greater volumes of water to the tributaries and to the creek - all at once - instead of slowly releasing the rainwater from the absorbent vegetated ground over time.

This instant runoff happens even during normal rainfall, let alone what we are experiencing now.  Before any work commences, the environmental community urges the Army Corps of Engineers, who designed the original project, to re-study and re-design the flood control on Chartiers Creek to address not only the current land use, but also to include newer technology and best management practices.   Such as using existing natural floodplains and riparian buffers to function as floodplains to collect and hold the overflow.

Abandoned mine drainage projects and federal stormwater mandates will also clean up the water quality.  This increases the recreational value of the creek.  It is not the open sewer it was a half-century ago when the flood control project was first implemented at the request of a handful of business owners, concurrent with the I-79 interstate planning and expected corridor business development.  

Dredging and clear-cutting now will only serve to destroy this emerging recreational resource for watershed residents.  Those of us interested in developing the creek's recreational potential urge the Chartiers Valley Flood Control Authority and the US Army Corps of Engineers to adopt an integrated approach to stormwater management that reflects the recreational uses of the creek and technical advancements of 2005 rather than sending the creek back to the way it was in 1965.

wake of the flood | natural floodplains | development | infrastructure 

WOODED SLOPES & NATURAL 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 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. 

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.  

wake of the flood | natural floodplains | development | infrastructure 

DEVELOPMENT

Low permeability clay soil makes vegetation even more important, as the vegetation holds the water, both on the leaves and in the roots, allowing it to slowly sink into the soil.  Vegetation decreases runoff and sedimentation into the creek.  In turn, this means lower peak water volume and less debris to fill up the channel needing to be dredged. Increased sedimentation in the Chartiers channel is very evident in the wake of Ivan.

The solution to the flooding problem cannot be
accomplished solely  by what is done on the creek, whether clear-cutting and dredging which increases the peak water volume, or diverting into natural floodplains which decreases the peak water volume.  

What will make the most difference is retaining the water on-site, upstream, in the uplands in order to lessen the runoff and sedimentation into the creek and its tributaries in the first place.  

While natural vegetation is most effective in retaining water and holding soil in place, what is needed in the developed areas is some form of stormwater management to retain the water on-site - whether it be retention ponds, permeable asphalt, disconnecting drain pipes, or remedial landscaping to increase vegetation. 

The downstream communities need to hold the upstream communities responsible for uncontrolled development.

wake of the flood | natural floodplains | development | infrastructure 

INFRASTRUCTURE

Low-lying bridges were inundated during hurricane Ivan and trapped the debris floating down the creek.  

The creek banks were also littered with downed trees and man-made debris, which will spur clean-up efforts this spring.

wake of the flood | natural floodplains | development | infrastructure