Anthony W. Holder

FLOTRAN, a three-dimensional ground water model, with comparisons to analytical solutions and other models☆

FLOTRAN is a ground water flow and transport model developed in the past few years which takes advantage of recent advances in numerical methodology. FLOTRAN solves the governing equations for flow and contaminant transport using Godunov-mixed methods, in which a higher-order Godunov method is used to approximate the advective flux, and a mixed finite element method is used for the dispersive transport. A mixed finite element method is also used to solve the flow equation. As part of the development of this new model, we have tested it against known analytical and numerical solutions to the equations approximated by the model. In this work, we have tested FLOTRAN against 1-D and 2-D analytical solutions, Galyas 3-D horizontal plane source solution, two radial semi-analytical solutions, and two numerical models, BIOPLUME II and MT3D. We have also tested FLOTRAN on a hypothetical partially saturated flow problem. FLOTRAN performed well on these tests, generally matching analytical solutions to within a few percent, and matching as well as or better than the other numerical models in most cases.

Modeling the Impact of Oxygen Reaeration on Natural Attenuation

Based on studies of leaking petroleum storage tank (LPST) sites in Texas and California, the average plume of benzene, toluene, ethylene, and xylenes (BTEX) is between 61 and 132 m (200 and 400 ft) long. Standard modeling of BTEX plumes produces plumes well in excess of observed plume lengths. The amount of oxygen carried into the plume zone with clean upgradient water often is insufficient to account for the levels of biodegradation observed in these studies. Traditional recharge of oxygen-containing water into an aquifer adds insufficient oxygen to the system and cannot account for the observed plume lengths. Research has shown that anaerobic processes can contribute to biodegradation in certain cases; however, anaerobic pathways are not included in this work. Reaeration of oxygen-depleted aquifers by diffusive transport of oxygen through the vadose zone has generally been neglected as a way to introduce oxygen into surficial aquifers. The observed plume lengths and preliminary laboratory results indica...

Modeling an Urban Drainage System with Large Tailwater Effects under Extreme Rainfall Conditions

When Tropical Storm Allison deluged southeast Texas in June 2001 it caused an estimated

Radar-Based Flood Warning System Applied to Tropical Storm Allison

5 billion in damages to the 28 counties declared as disaster areas. Approximately

A Radar-Based Flood Alert System (FAS) Designed for Houston, Texas

2 billion of this damage occurred at the Texas Medical Center in the Harris Gully watershed. The data collected during and after the storm, however, provides one of the most extensive databases ever available for the analysis of an urban flood. The calibrated SWMM model successfully simulated the observed T.S. Allison high water levels in Harris Gully. In a continuing study, the model is being used to evaluate potential mitigation options for the watershed.