This paper reports a laboratory study on violent geysers in a vertical pipe. Each geyser produced consists of a few consecutive violent eruptions within a time frame of a few seconds with heights that may exceed 30 m. Herein, the term “violent” is used to distinguish the present work from previous studies, which reported geyser heights that were relatively small compared to the present study. Previous work has speculated that the extreme behavior of geysers is driven by the buoyant rise of the air pocket in the vertical pipe. The present study shows that once the air pocket breaks through the free surface and produces a water spill, the horizontal pipe flow dynamics, in particular the rapidly changing pressure gradient following the first weak eruption, is driving the entire geyser mechanism.

In this study, we assess the costs and benefits of dynamic management of water storage to improve flood control in a system of wetlands. This management involves releasing water from wetlands ahead of (e.g., a few hours or days before) a rainfall event that is forecasted to produce flooding. Each project site may present different challenges and topographical conditions, however as long as there is a relatively small hydraulic gradient between the wetland water surface and the drainage ditch (e.g., >0.9 m), wetlands can be engineered for the purpose of flood control. We present a case study for a system comprised of four wetland areas encompassing 925 acres in the coastal plain south of Houston, Texas. The benefit–cost analysis shows that, in general, the benefits of wetland ecosystems far surpass the costs of construction and maintenance for all considered periods of analysis and assumed degrees of dynamic management of wetland storage. The analysis also shows that the benefit/cost ratios increase over the period of analysis. Considering flood protection only (e.g., not considering the value of other ecosystem services), as long as dynamic management of wetland storage increases flood protection by about 50% compared to that with no management (e.g., a typical wetland with no controlled release of water), the construction of a wetland system would have a benefit/cost ratio of at least 1.9.