Compound flooding in coastal areas emanating from inland and offshore events

Author

Hamed Behzad Koochaksaraii, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

5-31-2020

Degree Name

Doctor of Philosophy in Environmental Engineering - (Ph.D.)

Department

Civil and Environmental Engineering

First Advisor

Michel Boufadel

Second Advisor

Taha F. Marhaba

Third Advisor

Fadi A. Karaa

Fourth Advisor

Bruno M. Goncalves da Silva

Fifth Advisor

Zeyuan Qiu

Abstract

The vulnerability of urban populations to natural hazards and climate change is a major theme in many reports on coastal cities with flooding ranking highly among the climate change concerns. Flooding could occur as a result of runoff for inland rainfall that accumulates at the mouth of the estuary to the sea or it could occur due to a storm surge emanating from the ocean. The techniques for modeling the flooding from these events are very different, as they were developed in different scientific fields: hydrology and hydraulic engineering for inland rainfall versus coastal oceanography and coastal engineering for offshore storms. Therefore, there is no framework to combine the two approaches. Many studies have been conducted to show that there is a high probability of co-occurrence for these two events which is so-called compound flooding. Therefore, this research sought to provide a holistic framework that combines the two approaches.

The township of Old Bridge, New Jersey has been chosen as the study domain for this investigation. For flooding due to inland rainfall, SWMM (Storm Water Management Model) Software developed by the EPA has been used to provide the discharge to input to the model HEC-RAS (developed by U.S. Army Corps of Engineers). ArcGIS also used to extract the bathymetry profiles of the study domain and to define the land use properties, as those impact runoff speed and infiltration. Results for 100-year return period precipitation show more than a 3 ft of water level rise in the river which caused flooding in low areas. For offshore storms, data from Hurricane Sandy, extracted from the NOAA website, has been used for simulating the 100-year ocean storm. The two-dimensional analysis conducted using the CHAMP software, developed by the U.S. Army, to determine the storm surge, wave height in flooded lands, and wave run-up elevation. These were used to delineate the flooded zones according to FEMA specifications (AE and VE) based on the Sea Water Elevation (SWEL) and wave heights.

Finally, MIKE-21 software has been used to model the compound flooding in the study domain. The results from the MIKE-21 show that the inundation depth increases significantly during the compound flooding. Also, by applying a certain river flow rates on the different storm surges, it can be concluded that the water level rise due to rainfall has a reverse relationship with mean sea level elevation. It means as the storm surge increases in the coastal area, the effect of flooding caused by rainfall decreases.

Recommended Citation

Behzad Koochaksaraii, Hamed, "Compound flooding in coastal areas emanating from inland and offshore events" (2020). Dissertations. 1453.
https://digitalcommons.njit.edu/dissertations/1453