Evaluation of past,present and future tools for radar-based flash-flood prediction in the USA

Abstract

The societal impacts of flash floods are more significant than any other weather-related hazard. They are often manifested in the form of damage to infrastructure, flooding of roadways and bridges, creating deadly hazards to motorists and inundation of crops and pasture. Some of these hazards can be anticipated and thus mitigated given effective warning systems. This study describes the tools proposed over recent decades in the USA to predict flash flooding and evaluates them using a common observational data set. Design recommendations for flash-flood forecasting systems are provided, taking into account today's availability of high-resolution rainfall data at scales commensurate with flash flooding, their archives, spatial data sets to describe physiographic properties, and ever-increasing computational resources.

Editor D. Koutsoyiannis; Guest editor R.J. Moore

Citation Gourley, J.J., Flamig, Z.L., Hong, Y., and Howard, K.W., 2014. Evaluation of past, present and future tools for radar-based flash-flood prediction in the USA. Hydrological Sciences Journal, 59 (7), 1377–1389. http://dx.doi.org/10.1080/02626667.2014.919391     

Rolling Back the State and Physical Development Planning: The Case of Barbados

The focus of this paper is the recent preparation of the Third National Physical Development Plan for Barbados. Interestingly, this blueprint for the future development of the country was prepared by Canadian consultants, under the auspices of Inter-American Development Bank funding, and thereby ostensibly represents the rolling back of the State in the context of physical development planning. The paper briefly examines the origins of town and country planning in Barbados and the wider Caribbean before critiquing the Third Plan produced in 1998. Emphasis is placed on salient issues such as operationalising sustainable development, the involvement of local stakeholders, the role of Environmental Impact Assessments (EIA) in the planning process, and the production of Community Plans. Throughout, it is shown that whilst the State appears to have been "rolled back", government has retained its strong-hold over the course of physical development planning, principally by "tactics" which have served to minimise the degree to which members of the public and non-governmental organisations (NGOs) have been able to participate.     

A laboratory investigation into the effects of slope on lava flow morphology

In an attempt to model the effect of slope on the dynamics of lava flow emplacement, four distinct morphologies were repeatedly produced in a series of laboratory simulations where polyethylene glycol (PEG) was extruded at a constant rate beneath cold sucrose solution onto a uniform slope which could be varied from 1° through 60°. The lowest extrusion rates and slopes, and highest cooling rates, produced flows that rapidly crusted over and advanced through bulbous toes, or pillows (similar to subaerial “toey” pahoehoe flows and to submarine pillowed flows). As extrusion rate and slope increased, and cooling rate decreased, pillowed flows gave way to rifted flows (linear zones of liquid wax separated by plates of solid crust, similar to what is observed on the surface of convecting lava lakes), then to folded flows with surface crusts buckled transversely to the flow direction, and, at the highest extrusion rates and slopes, and lowest cooling rates, to leveed flows, which solidified only at their margins. A dimensionless parameter, Ψ, primarily controlled by effusion rate, cooling rate and flow viscosity, quantifies these flow types. Increasing the underlying slope up to 30° allows the liquid wax to advance further before solidifying, with an effect similar to that of increasing the effusion rate. For example, conditions that produce rifted flows on a 10° slope result in folded flows on a 30° slope. For underlying slopes of 40°, however, this trend reverses, slightly owing to increased gravitational forces relative to the strength of the solid wax. Because of its significant influence on heat advection and the disruption of a solid crust, slope must be incorporated into any quantitative attempt to correlate eruption parameters and lava flow morphologies. These experiments and subsequent scaling incorporate key physical parameters of both an extrusion and its environment, allowing their results to be used to interpret lava flow morphologies on land, on the sea floor, and on other planets.     

A heuristic framework for next-generation models of geostrophic convective turbulence

Many geophysical and astrophysical phenomena are driven by turbulent fluid dynamics, containing behaviors separated by tens of orders of magnitude in scale. While direct simulations have made large strides toward understanding geophysical systems, such models still inhabit modest ranges of the governing parameters that are difficult to extrapolate to planetary settings. The canonical problem of rotating Rayleigh-Bénard convection provides an alternate approach - isolating the fundamental physics in a reduced setting. Theoretical studies and asymptotically-reduced simulations in rotating convection have unveiled a variety of flow behaviors likely relevant to natural systems, but still inaccessible to direct simulation. In lieu of this, several new large-scale rotating convection devices have been designed to characterize such behaviors. It is essential to predict how this potential influx of new data will mesh with existing results. Surprisingly, a coherent framework of predictions for extreme rotating convection has not yet been elucidated. In this study, we combine asymptotic predictions, laboratory and numerical results, and experimental constraints to build a heuristic framework for cross-comparison between a broad range of rotating convection studies. We categorize the diverse field of existing predictions in the context of asymptotic flow regimes. We then consider the physical constraints that determine the points of intersection between flow behavior predictions and experimental accessibility. Applying this framework to several upcoming devices demonstrates that laboratory studies may soon be able to characterize geophysically-relevant flow regimes. These new data may transform our understanding of geophysical and astrophysical turbulence, and the conceptual framework developed herein should provide the theoretical infrastructure needed for meaningful discussion of these results.     

Ice cap erosion patterns from bedrock 10Be and 26Al,southeastern Tibetan Plateau

Quantifying glacial erosion contributes to our understanding of landscape evolution and topographic relief production in high altitude and high latitude areas. Combining in situ ¹⁰Be and ²⁶Al analysis of bedrock, boulder, and river sand samples, geomorphological mapping, and field investigations, we examine glacial erosion patterns of former ice caps in the Shaluli Shan of the southeastern Tibetan Plateau. The general landform pattern shows a zonal pattern of landscape modification produced by ice caps of up to 4000 km² during pre-LGM (Last Glacial Maximum) glaciations, while the dating results and landforms on the plateau surface imply that the LGM ice cap further modified the scoured terrain into different zones. Modeled glacial erosion depth of 0–0.38 m per 100 ka bedrock sample located close to the western margin of the LGM ice cap, indicates limited erosion prior to LGM and Late Glacial moraine deposition. A strong erosion zone exists proximal to the LGM ice cap marginal zone, indicated by modeled glacial erosion depth >2.23 m per 100 ka from bedrock samples. Modeled glacial erosion depths of 0–1.77 m per 100 ka from samples collected along the edge of a central upland, confirm the presence of a zone of intermediate erosion in-between the central upland and the strong erosion zone. Significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate restricted glacial erosion during the last glaciation. Our study, for the first time, shows clear evidence for preservation of glacial landforms formed during previous glaciations under non-erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the Haizishan ice cap during the LGM. © 2018 John Wiley & Sons, Ltd.     

On the waterfront: Quaternary environments and the formative occupation of Southwestern Ecuador

The occurrence of tectonic uplift in coastal South American prehistory is discussed and evidence of emerged shoreline features is presented for the area of the Santa Elena Peninsula in Ecuador. It is hypothesized that this activity, once thought to be exclusively Pleistocene in timing, continued on into the Holocene. Given this perspective and field data, the role of the Early Formative Period Valdivia phase (3500-1500 B.C.) site of Real Alto is examined, as is the economic structure of Real Alto society. the pattern of site distribution and data from geological units indicate a long period of tectonic activity that restructured the Ecuadorian coastline and affected northern Andean prehistory. the implications for the origins of Valdivia and New World pottery are reconsidered in light of new information on the Quaternary environments of Ecuador.     

Landforms as extended composite phenotypes

Biotic influences on geomorphology (and vice‐versa) are ubiquitous. This paper explores whether landforms may be extended (composite) phenotypes of biota, based on four criteria: process–form relationships between biota and landforms; evolutionary synchrony; selective pressure via ecosystem engineering and niche construction; and positive feedback benefitting the engineer organism(s). Coral reefs, peat bogs, biomantles, insect mounds, grassland soils, salt marshes, mangrove swamps, and some vegetation‐dependent sand dune types clearly meet these criteria. Karst landforms, meandering rivers, and tree uprooting pit‐mound systems meet the first three criteria, but positive feedback to engineer organisms has not been established. Research in biogeomorphology will surely identify other extended phenotypes. Implications are that biological evolution will continue to drive landscape metamorphosis, the appearance of new landform types, and presumably the disappearance of extended phenotypes associated with extinct species. Independently of extended phenotypes, tightly‐coupled geomorphological–ecological interactions such as coevolution, and biogeomorphic forms of ecosystem engineering and niche construction are common. The toposphere, encompassing Earth's landforms, is partly a biotic construct. Some elements would be present in an abiotic world, but the toposphere would not exist in anything resembling its contemporary state without a biosphere. This raises important questions with respect to Earth system evolution. The bio, litho‐, atmo‐, hydro‐, topo‐, and pedospheres coevolve at the global scale. Major biotic events have driven revolutions in the other spheres, but the atmosphere and the global hydrological system seem to have been relatively steady‐state at the global scale. The toposphere and pedosphere have not. This suggests that perhaps landforms and soils provide the major mechanisms or degrees of freedom by which Earth responds to biological evolution. Landforms and soils may thus be the ‘voice’ of the biosphere as it authors planetary change, even if clear biotic signatures are lacking. Copyright © 2015 John Wiley & Sons, Ltd.     

Digital landscapes of deglaciation: identifying Late Quaternary glacial lake outburst floods using LiDAR

High resolution DEMs obtained from LiDAR topographic data have led to improved landform inventories (e.g. landslides and fault scarps) and understanding of geomorphic event frequency. Here we use airborne LiDAR mapping to investigate meltwater pathways associated with the Tweed Valley palaeo ice‐stream (UK). In particular we focus on a gorge downstream of Palaeolake Milfield, previously mapped as a sub‐glacial meltwater channel, where the identification of abandoned headcut channels, run‐up bars, rock‐cut terrace surfaces and eddy flow features attest to formation by a sub‐aerial glacial lake outburst flood (GLOF) caused by breaching of a sediment dam, likely an esker ridge. Mapping of these landforms combined with analysis of the gorge rim elevations and cross‐section variability revealed a two phase event with another breach site downstream following flow blockage by higher elevation drumlin topography. We estimate the magnitude of peak flow to be 1–3 × 10³ m³/s, duration of the event to range from 16–155 days, and a specific sediment yield of 10⁷–10⁹ m³/km²/yr. We identified other outburst pathways in the lower Tweed basin that help delineate an ice margin position of the retreating Tweed Valley ice stream. The results suggest that low magnitude outburst floods are under‐represented in Quaternary geomorphological maps. We therefore recommend regional LiDAR mapping of meltwater pathways to identify other GLOFs in order to better quantify the pattern of freshwater and sediment fluxes from melting ice sheets to oceans. Despite the relatively low magnitude of the Till outburst event, it had a significant impact on the landscape development of the lower Tweed Valley through the creation of a new tributary pathway and triggering of rapid knickpoint retreat encouraging new regional models of post‐glacial fluvial landscape response. Copyright © 2015 John Wiley & Sons, Ltd.