Coastal Flooding Induced by Surcharging Storm Sewer Systems at Low Elevations
Abstract
While conventional stormwater sewer systems are intended to prevent flooding, these same systems installed at low elevations actually facilitate flooding. This flood hazard merits further investigation as the potential for economic damages on the low elevation bay side of developed barrier islands is significant. The potential for damages caused by elevated water levels in back bay systems separating barrier islands from the mainland has been largely overlooked in the recent study of coastal flooding hazards. This research addresses the challenge of identifying and documenting adverse consequences attributed to the common practice of allowing storm sewers to surcharge. One such region which suffers from chronic flooding facilitated by the stormwater sewer system is Seaside Park, NJ located on the Barnegat Barrier Island. There are large floods (up to .6 m) 3 to 4 times each year and minor floods (up to .2 m) 1 to 2 times each month. This study focuses on a .40 km stretch of Bayview Avenue which runs parallel to the bay and is protected by a bulkhead .76m high. A pressure transducer was installed to record time-series data of flood levels on the roadway. Comparing flood level time-series data with rainfall records and United States Geological Survey (USGS) tide gage readings, it is shown that surcharging storm sewers from elevated water levels in the bay is the primary mechanism causing flooding along Bayview Avenue. The contribution of surface runoff is shown to be minor in comparison with floods occurring even in the absence of rainfall. The critical water level for which flooding can be expected is determined for the Barnegat Bay USGS tide gage at Seaside Heights. Based on the real-time tide gage readings it is possible to predict when flooding will occur at to what level it will reach. This value is then used to sort historical records from the tide gage to determine that the frequency of flooding over time is increasing. Several hypotheses for this increase are presented. This study further investigates the effectiveness of the existing bulkhead installed to prevent flooding. A solution is purposed that retrofits the storm sewers to prevent surcharging thus increasing the effectiveness of the bulkhead structure and reducing the magnitude and frequency of flooding.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2007
- Bibcode:
- 2007AGUSM.H31B..08P
- Keywords:
-
- 1816 Estimation and forecasting;
- 1821 Floods;
- 1836 Hydrological cycles and budgets (1218;
- 1655);
- 1899 General or miscellaneous