DEVELOPMENT
denuded hillsides like this increase erosion, runoff and landslides which negatively impact the economics of low-lying downstream communities

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.

gravel bar forms at edge of creek by incoming tributary. Note how close development is to the creek.

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.  
closeup of sediment deposits. Much of the sediment was eroded from steep slopes in over-developed areas.

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.  

scour from floodwaters and subsequent landslide

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. 

new sand bars form beaches along Chartiers Creek

The downstream communities need to hold the upstream communities responsible for uncontrolled development.
another new beach on Chartiers Creek invites recreational opportunity

Bars of sediment form where each tributary flows into Chartiers Creek.  And a very large sand bar forms in McKees Rocks where Chartiers Creek flows into the Ohio River.  While these sand deposits are a natural occurrence - the result of a change in water velocity from one stream to the next - their presence creates more flooding during stormwater events.

debris, consisting of dead wood and junk, piles up along shoreline. While live trees were laid down by the flood, they do not break and have mostly recovered.

Dredging will remove the sand bars.  But they will keep forming unless the upstream communities do their part to lessen stormwater runoff and excess soil erosion that add to the sediment problem.  The upstream communities need to enact ordinances to make developers responsible for holding stormwater on site and for replacing and adding the proper vegetation to curb soil erosion.