| A numerical study is conducted to simulate the oscillations (storm surges) of semi-enclosed water body induced by hurricanes. For application using the numerical model developed in the present study, Lake Pontchartrain (located in southeastern Louisiana) is chosen as the semi-enclosed water body and Hurricane Katrina (the costliest hurricane in the history of the United States) is chosen as the hurricane. There are three (3) reasons to choose Lake Pontcharrain and Hurricane Katrina: 1. Storm surge built up in Lake Pontchartrain during Hurricane Katrina, 2. Wind drove water into Lake Pontchartrain as Hurricane Katrina approached from the Gulf of Mexico, and 3. The extensive field data, gathered by the Interagency Performance Evaluation Task Force (IPET), is available to provide the needed comparison of numerical result and prototype data on the oscillations at Lake Pontchartrain induced by Hurricane Katrina.;The depth-average, non-linear shallow-water equations (NLSW) are use as the governing equations. The finite-volume method (FVM) is employed to solve the governing shallow-water equations. In order to validate the present model, the hydrographs due to Hurricane Katrina obtained from the present model are compared with the field data reported by IPET at eight (8) sites along the shores and the center of Lake Pontchartrain. These eight (8) sites are: the 17th street Canal, the Orleans Avenue Canal, the London Avenue Canal, the Inner Harbor Navigation Canal (IHNC)-Lakefront Airport, Midlake, Bayou Labranch, Pass Manchac, and Little Irish Bayou.;The time at which the maximum water surface elevation (WSE) occurs as predicted by the present model is almost identical to the time at which the maximum water level is observed at the 17th Street Canal, the Orleans Avenue Canal, the London Avenue Canal, and the IHNC-Lakefront Airport sites. Furthermore, the present model correctly predicts the general trend of the water level when the hydrographs due to Hurricane Katrina are compared with the observed hydrographs at the 17th Street Canal, the Orleans Avenue Canal, the London Avenue Canal, the IHNC-Lakefront Airport, and the Midlake sites. However, the present model only reasonably predicts the general trend of the water level when the hydrographs due to Hurricane Katrina are compared with the observed hydrographs at the Bayou La Branche (named Bayou Labranch by IPET), the Pass Manchac, and the Little Irish Bayou sites.;The present model is further applied to investigate the oscillations at Lake Pontchartrain induced by four (4) synthetic hurricanes within the time-span of 00:00 UTC August 29, 2005 to 00:00 UTC August 30, 2005: Case 1. Hurricane Katrina tracks on its original route, Case 2. Hurricane Katrina tracks 36 km west of its original route, Case 3. Hurricane Katrina tracks 72 km west of its original route, and Case 4. Hurricane Katrina tracks on its original route with forward speeds reduced by 16% ∼ 45% (or altered from 15 km/h ∼ 36 km/h to 15 km/h ∼ 22 km/h). These are done to assess the impact of hurricanes under different risk conditions. It is found that much more severe catastrophes in metro New Orleans and neighboring parishes can be expected under the scenarios of: Case 2. Hurricane Katrina passes through the east part of New Orleans, Louisiana and both the east and central parts of Lake Pontchartrain and Case 4. Hurricane Katrina passes through the regions nearby the east shore of Lake Pontchartrain with reduced forward speeds. |
