Daniel Mendelsohn

Application of an Integrated Blowout Model System, OILMAP DEEP, to the Deepwater Horizon (DWH) Spill

OILMAP DEEP, an integrated system of models (pipeline release, blowout plume, dispersant treatment, oil droplet size distribution, and fountain and intrusion), was applied to the Deepwater Horizon (DWH) oil spill to predict the near field transport and fate of the oil and gas released into the northeastern Gulf of Mexico. The model included multiple, time dependent releases from both the kink and riser, with the observed subsurface dispersant treatment, that characterized the DWH spill and response. The blowout model predictions are in good agreement with the available observations for plume trapping height and the major characteristics of the intrusion layer. Predictions of the droplet size distribution are in good agreement with the limited in situ Holocam observations. Model predictions of the percentage of oil retained in the intrusion layer are consistent with independent estimates based on field observations.

Modeling Subsurface Dispersant Applications for Response Planning and Preparation

ABSTRACT The increase in oil and gas development activity at increasing water depths has highlighted the need for modeling tools to evaluate the unique aspects of accidental deepwater releases, one...

A Simplified Method for Marsh Inundation Modeling in Hydrodynamic and Water Quality Models with Application to the Cooper River Estuary (SC)

A simplified method for incorporation of the marsh inundation effects on the circulation and transport within an estuary is proposed, with the use of a special marsh boundary condition. The marsh boundary has two basic features; determination of flow in and out, and storage of water, salinity, heat and constituent in the marsh. A particular marsh is specified by a set of physical parameters that include the surface area, front elevation referenced to mean sea level (i.e. when the marsh will flood), back elevation (affects marsh volume), flow length and porosity (growth density) of the marsh. Flow in and out of the marsh is modeled with a reduced momentum equation, which varies dependent on flow regime and is influenced by the specified Manning friction factor, marsh flooding length, and predicted values of marsh water elevation. Test cases run indicate that the two more sensitive parameters in the marsh boundary cell calculations are the marsh surface area and the marsh gradient length (from the reduced momentum equation in the boundary condition). For short gradient lengths the discharge is significantly larger than for the longer values. In addition increasing the marsh surface area has little effect on the discharge after an initial increase in response at small surface areas, whereas the concentration of salt or constituent will respond more slowly for the larger areas. An example application is presented where the marsh boundary was used to model the impact of extensive salt marshes and former rice paddies along the Cooper River, South Carolina. Model predicted surface elevations at the head of estuarine Cooper River, are over-predicted where no marsh boundary cells were used. When marsh boundary cells are used the effect is to damp the tidal amplitude, by draining off large volumes of water, thereby matching observations.

The Alyeska Tactical Oil Spill Model

An innovative oil spill model system for the Prince William Sound region, a model developed for Alyeska Pipeline Service Company is described. The model system includes modules to simulate the surface and subsurface movement of oil, the tactics, operational constraints, and effectiveness of spill response (dispersant, mechanical cleanup, and burning), and the environmental impact of the spill on the biota of the Sound. The model system is impelmented in a personal computer workstation environment with a graphical interface including mouse-driven menus, color overlay mapping, and animations of model predictions. A commercial database system is employed to organize and present information on spill response resources, shoreline types, and biological resources. Water surface, water column, and shoreline biota are included in the biological database, as are critical habitats for these organisms. A mesoscale meteorological model, which explicitly includes orographic effects, is employed to predict wind fields. A three dimensional hydrodynamic model estimates the tide, wind and density induced circulation.

Modeling the Impacts of Water Withdrawls on the Thermal Regime of the Weeki Wachee River Winter Manatee Habitat

The Southwest Florida Water Management District is required to develop Minimum Flows and Levels. The MFL for Weeki Wachee Springs was developed to protect the West Indian Manatee, which utilize the warm Spring waters as a refuge when offshore waters go below tolerable levels. A 3D-hydrodynamic model application was developed using the EFDC to predict offshore water intrusion into the Weeki Wachee. The 2003-2005 model calibration focused on water surfaced elevation, salinity and temperature in the river. The model was applied under critical temperature conditions, and low and high flow baseline Spring conditions upon which reduced flows were applied. Manatee habitat refuge areas and volumes were defined as waters that met the following criteria: ∞ Daily average temperatures >20°C over a 3-day period ∞ Minimum manatee passage of 3.8 ft depth available upstream Incremental flow reductions were applied until the manatee refuge area or volume reduction was >15%, representing the maximum allowable flow reduction. During low offshore temperatures with low spring flow, a 5% spring flow reduction resulted in a 15% reduction in manatee habitat area/volume. The available manatee refuge is capable however, of supporting over 1363 manatee, well above the present number that utilize Weeki Wachee Springs.