Valtellina landslide and flood emergency, northern Italy, 1987

This report describes the progress of the landslide and flood emergency that occurred in Valtellina, in the northern Italian Alps, during July and August 1987. For the authorities, the critical problem was one of controlling the rise of a large lake impounded on the River Adda by landslide debris that threatened to breach catastrophically, releasing a major floodwave. Several lessons can be learned from the way in which the emergency was managed. First, helicopters played a critical role in evacuating survivors and moving supplies around the disaster area, but there was scope for better co-ordination of operations. Secondly, high levels of private car ownership allowed greater flexibility in designing mass evacutation plans for threatened communites, but such high personal mobility proved difficult to control in order to ensure public safety. In future, education programmes could be used to help people appreciate the dangers of driving during periods of great natural hazard risk. Thirdly, the Valtellina disaster coincided with a change of national government, including substitution of the Minister of Civil Protection. This led to a policy vacuum, sub-optimal decision making and erosion of public confidence in political leaders. Landslide-dammed lakes represent a widespread but rather unpredictable hazard: they therefore require flexible emergency repsonse, but not without decisive leadership.     

Effects of seasonal perturbations on a model plankton community

The dynamic behaviour of a model plankton community is described by solutions of a generalized predator‐prey model. The qualitative changes due to variations of parameters are considered and the existence of multistability and catastrophic behaviour is noted. Local and global bifurcations of the system are displayed. A seasonal variation of a parameter is introduced and the resulting dynamics are considered, such as quasiperiodic solutions or chaotic attractors.     

Regulatory off-gas analysis from the evaporation of Hanford simulated waste spiked with organic compounds

After strontium/transuranics removal by precipitation followed by cesium/technetium removal by ion exchange, the remaining low-activity waste in the Hanford River Protection Project Waste Treatment Plant is to be concentrated by evaporation before being mixed with glass formers and vitrified. To provide a technical basis to permit the waste treatment facility, a relatively organic-rich Hanford Tank 241-AN-107 waste simulant was spiked with 14 target volatile, semi-volatile, and pesticide compounds and evaporated under vacuum in a bench-scale natural circulation evaporator fitted with an industrial stack off-gas sampler at the Savannah River National Laboratory. An evaporator material balance for the target organics was calculated by combining liquid stream mass and analytical data with off-gas emissions estimates obtained using U.S. Environmental Protection Agency (EPA) SW-846 Methods. Volatile and light semi-volatile organic compounds (<220 degrees C BP, >1 mm Hg vapor pressure) in the waste simulant were found to largely exit through the condenser vent, while heavier semi-volatiles and pesticides generally remain in the evaporator concentrate. An OLI Environmental Simulation Program (licensed by OLI Systems, Inc.) evaporator model successfully predicted operating conditions and the experimental distribution of the fed target organics exiting in the concentrate, condensate, and off-gas streams, with the exception of a few semi-volatile and pesticide compounds. Comparison with Henry's Law predictions suggests the OLI Environmental Simulation Program model is constrained by available literature data.     

A FAST RECURSIVE GIS ALGORITHM FOR COMPUTING STRAHLER STREAM ORDER IN BRAIDED AND NONBRAIDED NETWORKS1

ABSTRACT: Stream ordering is a useful property of every river network, having a wide range of applications. A method for determining stream orders that quickly and easily addresses various network topologies and magnitudes is therefore needed. This paper introduces a general recursive stream ordering framework for vector hydrography. It also presents a linear, O(n), stream ordering procedure for braided river networks, which is a major improvement to the existing quadratic, O(n²), procedure. The discussion includes results and interpretations, and the appendices present procedure pseudocodes and thorough line by line explanations.     

TRENDS IN LEAD CONCENTRATIONS IN MAJOR U.S. RIVERS AND THEIR RELATION TO HISTORICAL CHANGES IN GASOLINE-LEAD CONSUMPTION1

ABSTRACT: Declines in concentrations of dissolved lead occurred at nearly two-thirds of 306 locations on major U.S. rivers from 1974 to 1985. Declines in dissolved lead concentrations are statistically significant (p < 0.10) at approximately one-third of the sampling locations. Statistically significant increases in dissolved lead concentrations occurred at only 6 percent of the sites, but are clustered in the Texas-Gulf and Lower Mississippi regions. Possible explanations for the observed trends in lead concentrations are tested through comparisons with (1) records of lead discharges from major sources including leaded-gasoline consumption and municipal- and industrial-point source discharges, (2) trends in various water-quality constituents such as pH and total alkalinity, and (3) basin characteristics such as drainage area. Statistically significant declines in lead concentrations in streams and gasoline lead (i.e., the largest source of lead at these sites) are highly coincident for the 1979 to 1980 period at most sampling locations. The greatest amount of decline in gasoline lead occurred at sites showing statistically significant downtrends in stream concentrations of lead from 1974 to 1985. No more than 5 percent of the trends in stream lead are influenced by municipal- and industrial-point sources of lead. Factors that affect the transport of dissolved lead, including lead solubility, suspended sediment, and basin characteristics such as drainage basin size, are not significantly related to trends in dissolved lead. Trends in streamflow explain no more than 7 percent of the downtrends in concentrations of lead and may partly explain the frequent increases in lead concentrations in the Texas-Gulf and Lower Mississippi regions.     

Apportionment of nuptial alkaloidal gifts by a multiply-mated female moth (Utetheisa ornatrix): eggs individually receive alkaloid from more than one male source

Summary. In the moth Utetheisa ornatrix the female is promiscuous and receives a nuptial gift of pyrrolizidine alkaloid (PA) by seminal infusion from each mate. The alkaloidal gifts are transmitted by the female to the eggs, which are protected as a result. We here show that individual eggs may receive PAs from more than one male source and that individual males have no assurance that the PA they themselves contribute to the female will find its way exclusively to eggs of their siring. Received 28 June 2002; accepted 28 August 2002.     

Corematal function in Utetheisa ornatrix: interpretation in the light of data from field-collected males

Summary. Males of the moth Utetheisa ornatrix produce a pheromone, hydroxydanaidal, contained in two brush-like organs, the coremata, which they evert during courtship. Hydroxydanaidal is derived chemically by the males from pyrrolizidine alkaloids that they sequester from their larval food plants. It had been shown previously that the amount of hydroxydanaidal in the coremata correlates positively with a number of male parameters that are a measure of the male’s “worth.” Hydroxydanaidal could thus be used by the female as a basis for discrimination in courtship. Experiments carried out with virgin Utetheisa had shown that females do indeed mate selectively with males of high corematal hydroxydanaidal content, thereby accruing the multiple benefits that are the consequence of such selectivity. Unresolved was the question whether corematal hydroxydanaidal could still provide a basis for female appraisal of suitors when these had previously mated. Given the proven promiscuity of the female, male Utetheisa could be expected to be promiscuous as well. Evidence we present here shows that field-collected males, which could be expected to be mostly non-virginal, are of reduced acceptability to females. They are also, on average, in possession of lower quantities of hydroxydanaidal, explaining possibly why they should be held in lesser regard. At low levels, however, hydroxydanaidal does not lend itself for precise assessment of male worth, because as we show herein, at such levels, the compound does not correlate with any of the criteria of male quality (male size, spermatophore mass, male pyrrolizidine alkaloid content, amount of pyrrolizidine alkaloid transmitted to the female). Males that have mated beforehand are therefore likely not to be classed into subcategories by the females, but simply as belonging to one category of “less desirables”. The significance of these findings to our understanding of the mating strategy of Utetheisa is discussed.     

Using land as a control variable in density-dependent bioeconomic models

The bioeconomic analysis of endangered species without consumptive values can be problematic when analysed with density-dependent models that assume a fixed environment size. Most bioeconomic models use harvest as a control variable, yet when modelling non-harvestable species, frequently the only variable under control of conservationists is the quantity of habitat to be made available. The authors explore the implications of this in a model developed to analyse the potential population recovery of New Zealand’s yellow-eyed penguin. The penguin faces severe competition with man for the terrestrial resources required for breeding and has declined in population to perilously low levels. The model was developed to estimate the land use required for recovery and preservation of the species and to compare the results to current tourism-driven conservation efforts. It is demonstrated that land may serve as a useful control variable in bioeconomic models and that such a model may be useful for determining whether sufficient incentives exist to preserve a species. However, the model may generate less useful results for providing a specific estimate of the optimal allocation of land to such a species.