At a public meeting on December 18, engineers delivered the results of their Local Flood Analysis (LFA) for the hamlets of Shandaken and Allaben, within the town of Shandaken. Recommendations for future flood resilience include relocating the town hall complex out of the flood zone; enlarging two bridges on Fox Hollow Road only if damaged or scheduled for replacement; monitoring the stream bottom at a bridge on Creekside Road and cautiously removing sediment if warranted; elevation of homes or electrical structures within buildings in the flood zone.
The LFA was funded by New York City to evaluate the feasibility and effectiveness of various flood control measures, including dredging, floodplain modification, removal of sediment bars, replacing bridges, and relocation of buildings in the floodplain. Using FEMA flood data for the Esopus Creek, computer modeling, and feedback from local residents, Milone and MacBroom, the town’s engineering firm, made a cost-benefit analysis for a series of proposed projects. Recommendation by an LFA opens up funding sources for many possible projects.
Project manager Mark Carabetta said previous LFA assessments in Phoenicia and Mount Tremper determined that floodplain enhancement projects there would be cost-effective. But such actions would involve carving out land along the creek, an expensive prospect, and given the low population density of the western hamlets, the amount of predicted damage prevention would not make such projects worthwhile in Shandaken and Allaben.
In general, based on computer modeling, removal of sediment from the creek bottom under bridges was shown to have some effect in small storms but no appreciable effect in larger floods. One exception was the bridge at Creekside Road, near the junction of Routes 28 and 42. Carabetta said conditions there should be monitored, with digging out of sediment a cost-effective option if the bottom rises too close to the bridge. Dredging, however, must be done with care and based on hydraulic studies, to prevent causing even more serious problems upstream or downstream.
Bridges contribute to flooding by backing up water as it attempts to pass beneath an undersized bridge, but attempting to enlarge bridges in the two hamlets would not be cost-effective in most cases. Where the floodplain is very wide, the bridge would have to be extended farther than practical to have any effect. Two bridges on Fox Hollow, however, would be worth enlarging if they sustain damage or are scheduled for replacement.
Engineers closely studied the confluence of the Bushnellsville and Esopus Creeks at the bottom of Route 42, where the configuration of the water flow was drastically changed by Hurricane Irene in 2011. No major modifications there would be cost-effective, but armoring of the levee is recommended if erosion seems likely.
Erosion downstream from Shandaken Portal
Shandaken Area Flood Assessment and Remediation Initiative (SAFARI), a coalition of local agencies and interest groups, brought up concerns about erosion downstream from the Shandaken Portal at Broadstreet Hollow. The Esopus in that area was previously divided into two channels, allowing more flexibility during flooding. Repair of serious damage from the 2011 flood led to closure of the secondary channel. Computer modeling showed improved results with two channels, but further hydraulic studies would be required to assess the practicality of such a project.
The town highway garage and dog pound are located in the floodway, and their parking lot underwent major flooding during Hurricane Irene. The town hall itself is also within a flood zone. The entire complex is under consideration for relocation to Route 28, east of Phoenicia, based on evaluation by the state’s NY Rising program two years ago. The LFA concurred with this recommendation. The Catskill Watershed Corporation (CWC) has already approved funds to purchase the property that may be used to construct a new town hall complex.
Shandaken and Allaben have a small number of buildings that are located in flood zones, and the LFA suggests measures to either remove or preserve them. Flood buyout programs are available from New York City, which would reimburse the owners and demolish the structures. Some homes could be elevated above the floodplain, while others would benefit from simply having electrical equipment and appliances raised up within the buildings. The town should enforce floodplain regulations and prevent any new development within the floodway.
To view the LFA report, go to http://www.shandaken.us, click on “Disaster Prep,” and choose “Flood Mitigation Plan,” then select “Final Draft of the LFA Report.” A copy is also available for perusal at the town hall.