This is has been a point of contentious flooding for years. Under lack environmental regulations and township permitting the original developer modified the location of the stream resulting in unplanned stream-channel geomorphic response. The flow length was increased, resulting in decreased slope and ultimately decreased channel capacity. The decreased slope lowers the velocity of the stream and perpetuates sediment depositions. Rather than having a stream flowing with its natural velocity and keeping the main channel clean, sediment now deposits in the stream. Lack of side bank maintenance then becomes an issue as invirase vegetation quickly establishes in the sediment deposits further contributing to the conveyance issues.
Photo shows the long term build up of sediment deposit that has significantly reduced the sidewall and channel capacity.
Permits have been requested for routine sediment maintenance.
We will utilize the overall watershed assessment that is being completed to address upstream detention improvements with the goal of lowering the peak flows. We also anticipate a large stream restoration project to be identified in the watershed assessment. This would include reconnecting the floodplain, providing channel capacity and stabilizing the stream with rock vanes, j-hooks, and grade control devices. In the interim we have applied for a USCOE/PADEP Joint Permit to remove the surface sediment accumulations and provide some bank height at the current overtopping location. The new property owner has begin maintaining the stream banks. This will greatly improve conveyance and reduce obstructions during high flow events.
While flood planning is conducted and permits are secured for more complex operations, less difficult measures are being taken to make immediate impacts.
For example, removing and then maintaining overgrown weeds and other vegetation aids in the free flow of water and helps to reduce the frequency of overflows. As you see from the photos below, the property owner’s investment in this maintenance is significant.
BEFORE: vegetation/ weeds prohibits the free-flow of water
AFTER: The removal of excess vegetation while retaining the root structures aids in the flow of water while reducing erosion.