Joseph E. Dove

Can urban tree roots improve infiltration through compacted subsoils for stormwater management

Global land use patterns and increasing pressures on water resources demand creative urban stormwater management. Strategies encouraging infiltration can enhance groundwater recharge and water quality. Urban subsoils are often relatively impermeable, and the construction of many stormwater detention best management practices (D-BMPs) exacerbates this condition. Root paths can act as conduits for water, but this function has not been demonstrated for stormwater BMPs where standing water and dense subsoils create a unique environment. We examined whether tree roots can penetrate compacted subsoils and increase infiltration rates in the context of a novel infiltration BMP (I-BMP). Black oak (Quercus velutina Lam.) and red maple (Acer rubrum L.) trees, and an unplanted control, were installed in cylindrical planting sleeves surrounded by clay loam soil at two compaction levels (bulk density = 1.3 or 1.6 g cm(-3)) in irrigated containers. Roots of both species penetrated the more compacted soil, increasing infiltration rates by an average of 153%. Similarly, green ash (Fraxinus pennsylvanica Marsh.) trees were grown in CUSoil (Amereq Corp., New York) separated from compacted clay loam subsoil (1.6 g cm(-3)) by a geotextile. A drain hole at mid depth in the CUSoil layer mimicked the overflow drain in a stormwater I-BMP thus allowing water to pool above the subsoil. Roots penetrated the geotextile and subsoil and increased average infiltration rate 27-fold compared to unplanted controls. Although high water tables may limit tree rooting depth, some species may be effective tools for increasing water infiltration and enhancing groundwater recharge in this and other I-BMPs (e.g., raingardens and bioswales).

Transpiration and Root Development of Urban Trees in Structural Soil Stormwater Reservoirs

Stormwater management that relies on ecosystem processes, such as tree canopy interception and rhizosphere biology, can be difficult to achieve in built environments because urban land is costly and urban soil inhospitable to vegetation. Yet such systems offer a potentially valuable tool for achieving both sustainable urban forests and stormwater management. We evaluated tree water uptake and root distribution in a novel stormwater mitigation facility that integrates trees directly into detention reservoirs under pavement. The system relies on structural soils: highly porous engineered mixes designed to support tree root growth and pavement. To evaluate tree performance under the peculiar conditions of such a stormwater detention reservoir (i.e., periodically inundated), we grew green ash (Fraxinus pennsylvanica Marsh.) and swamp white oak (Quercus bicolor Willd.) in either CUSoil or a Carolina Stalite-based mix subjected to three simulated below-system infiltration rates for two growing seasons. Infiltration rate affected both transpiration and rooting depth. In a factorial experiment with ash, rooting depth always increased with infiltration rate for Stalite, but this relation was less consistent for CUSoil. Slow-drainage rates reduced transpiration and restricted rooting depth for both species and soils, and trunk growth was restricted for oak, which grew the most in moderate infiltration. Transpiration rates under slow infiltration were 55% (oak) and 70% (ash) of the most rapidly transpiring treatment (moderate for oak and rapid for ash). We conclude this system is feasible and provides another tool to address runoff that integrates the function of urban green spaces with other urban needs.

Adaptive and Real-Time Geologic Mapping, Analysis and Design of Underground Space (AMADEUS)

This paper describes the design and implementation of an Information Technology (IT)-based system called AMADEUS for adaptive and real-time geologic mapping, analysis, and design of underground space. Advances in IT, particularly in digital imaging, data management, visualization and computation can significantly improve analysis, design and construction of underground excavations. Using IT, real-time data on geology and excavation response can be gathered during the construction using non-intrusive techniques which do not require expensive and time-consuming instrumentation. The real-time data are then used to update the geological and computational models of the excavation, and to determine the optimal rate of excavation, excavation sequence and structural support. Virtual environment (VE) systems are employed to allow virtual walk-through inside an excavation, observe geologic conditions, perform virtual tunneling operations, and investigate stability of the excavation via computer simulation.

Semiautomatic Rock Mass Discontinuity Detection using Digital Images

Manual fracture mapping in tunnels, caverns, mines or other underground spaces is a time intensive and sometimes dangerous process. A system to automate this task can minimize human exposure to rockfalls, rockbursts or instabilities and facilitate the use of new methods of data visualization. This paper describes the program VTtrace; a semi-automatic fracture mapping algorithm based on image processing and analysis techniques. Fracture map and fracture properties are obtained from digital images using a series of image processing and analysis algorithms. Results from test images shows the VTtrace is effective in extracting rock discontinuity traces.