Theodore Caplow

Transport in the Hudson Estuary: A Modeling Study of Estuarine Circulation and Tidal Trapping

The effects of estuarine circulation and tidal trapping on transport in the Hudson estuary were investigated by a large-scale, high-resolution numerical model simulation of a tracer release. The modeled and measured longitudinal profiles of surface tracer concentrations (plumes) differ from the ideal Gaussian shape in two ways: on a large scale the plume is asymmetric with the downstream end stretching out farther, and small-scale (1–2 km) peaks are present at the upstream and downstream ends of the plume. A number of diagnostic model simulations (e.g., remove freshwater flow) were performed to understand the processes responsible for these features. These simulations show that the large-scale asymmetry is related to salinity. The salt causes an estuarine circulation that decreases vertical mixing (vertical density gradient), increases longitudinal dispersion (increased vertical and lateral gradients in longitudinal velocities), and increases net downstream velocities in the surface layer. Since salinity intrusion is confined to the downstream end of the tracer plume, only that part of the plume is effected by those processes, which leads to the largescale asymmetry. The small-scale peaks are due to tidal trapping. Small embayments along the estuary trap water and tracer as the plume passes by in the main channel. When the plume in the main channel has passed, the tracer is released back to the main channel, causing a secondary peak in the longitudinal profile.

Homelessness, Affiliation, and Occupational Mobility

Affiliation and employment histories obtained from a sample of skid-row men and a control sample of residents in a low-income metropolitan census tract are used in a test of the hypotheses that skid-row men are less affiliated than lower-class men in settled neighborhoods, and that downward occupational mobility is associated with loss of affiliations. Compared with the control sample, skid-row men have long histories of low affiliation, both before and after their arrival on skid row. The two samples did not differ much in occupational mobility, but their affiliative patterns have been quite different. Apparently the disaffiliation of skid-row men cannot be attributed to their downward mobility. Whether downward mobility is accompanied by disaffiliation seems to depend on the context in which it occurs. D espite a long tradition of research dealing with homeless men, many crucial questions about the phenomenon of homelessness remain to be answered. Numerous studies of vagrants, beggars, hobos, and other isolated persons have provided insight into the way homeless people live, but there are few thorough explorations of the social origins and consequences of homelessness. During the past 15 years the situation has changed somewhat. In preparation for urban renewal, Sacramento, Chicago, Minneapolis, and Philadelphia have completed large-scale action-oriented surveys of their skid rows.1 These studies have provided descriptions of skid row and its men, but have not answered some fundamental questions about the development of homelessness. The present paper examines one of these questions, that of the relation between occupational mobility and dis-