Browsing by Subject "Heat"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Modeling Stream Thermal Dynamics: The Influence of Beaver Dams in a Minnesota Watershed
    (2020-08) Behar, Hannah
    Beaver dams are known to alter the thermal regime of ponds, streams, and adjacent subsurface waters. Downstream of a dam, stream temperature is influenced by increased exchange with the hyporheic zone, which may cool and buffer the stream’s diel temperature cycles. Concurrently, reduced shading in the beaver forage zone is likely to increase heat flux at the stream-atmosphere boundary. The dynamics of these processes can be analyzed to understand how stream temperature is affected on diel time scales, as well as longitudinally at distances downstream from the dam. At two beaver dam-impacted stream sites in the Knife River Watershed in Minnesota, USA, I monitored in-stream and shallow subsurface flow and temperature during low-flow summer conditions. I used a dye tracer test, vertical heat transport modelling, and soil characterization to estimate flux through the streambed at multiple locations. Temperature, stream flow, and atmospheric data were also collected throughout the summer from the two sites. A one-dimensional model of longitudinal stream temperature, calibrated to in-stream temperature measurements, was developed to determine which physical parameters and heat flux components have the greatest influence on stream temperature. The model was then used to demonstrate how these changes persist downstream, as well as to simulate stream temperature under potential future site conditions. These findings increase scientific understanding of stream temperature regime in the context of beaver dam-altered watersheds.
  • Thumbnail Image
    Item
    Temperature, Heat Waves, Crime, and Injuries in Hanoi, Vietnam
    (2022-12) Le, Vu Thuy Huong
    Manuscript 1: The effects of temperature on behavior change and mental health have previously been explored, but the association between temperature and crime is less well understood, especially in developing countries. Single-city-level data were used to evaluate the association between the short-term effects of temperature on crime events in urban Hanoi, Vietnam. We used quasi-Poisson regression models to investigate the linear effects and distributed lag non-linear models to investigate the non-linear association between daily temperature and daily crime events from 2013 to 2019. There were 3884 crime events, including 1083 violent crimes and 2801 non-violent crimes, during the 7-year study period. For both linear and non-linear effects, there were positive associations between an increase in daily temperature and crime, and the greatest effects were observed on the first day of exposure (lag 0). For linear effects, we estimated that each 5 °C increase in daily mean temperature was associated with a 9.9% (95%CI: 0.2; 20.5), 6.8% (95%CI: 0.6; 13.5), and 7.5% (95%CI: 2.3; 13.2) increase in the risk of violent, non-violent, and total crime, respectively. For non-linear effects, however, the crime risk plateaued at 30 °C and decreased at higher exposures, which presented an inverted U-shape response with large statistical uncertainty. Manuscript 2: Heatwaves are a pervasive natural hazard that can have significant public health impacts on society. The effects of heatwaves on health, including mental health disorders, are well documented, but the effects on criminal behavior are unclear, particularly in understudied tropical regions. This study evaluates the heatwave-crime associations in urban Hanoi, Vietnam, for seven years (2013- 2019). The time-stratified case-crossover study design with a quasi-Poisson regression model was applied for three heatwave definitions of increasing severity. We found that heatwaves were weakly protective factors against crime risk in urban Hanoi under all three heatwave definitions. For non-violent crime, 4-day heatwaves of 34.5 °C showed the most protective effect (RR=0.28, 95%CI = 0.08, 0.94), and for violent crime, 2-days heatwave of 32 °C showed the most protective effect (RR= 0.65; 95%CI = 0.45; 0.93). In addition, longer heatwave durations under all heatwave scenarios decreased violent and non-violent crime risks. However, we used data in only urban Hanoi, so further research is warranted, including the addition of future years and more cities in Vietnam to investigate the comprehensive effects of heat on crime in this southeast Asian study area. Manuscript 3: Injuries take the lives of 4.4 million people worldwide each year and constitute nearly 8% of all deaths. Vietnam, considered a low-and-middle-income country (LMIC), has suffered a heavy toll on the burden of injury. This is the first study to investigate temperature-injury associations in Vietnam. This study used emergency visit data from 733 hospitals and clinics in Hanoi to examine the linear and non-linear effects of temperature on the injury for three years (2017-2019). We found that the proportion of males visiting the emergency department (ED) due to injury is higher than females, and similar trends are observed across different age groups, except for people aged 60 and older. The temperature-injury associations differ by gender and age. For linear effects, the lowest risk was in people aged 60 and older, followed by people aged under 15, people aged 15 to 44, and people aged 45- 59. People exposed to a higher temperature, especially in the highest quintile, show higher injury risk than those exposed to below 21.30 °C. For non-linear effects, we observed an increase in the risk of injury at high temperatures but a decrease in the risk of injury at low temperatures compared to the threshold temperature of 15 °C. Males have a higher injury risk than females when temperature increases. On average, males and people under 60 were identified to be at higher risk of temperature-related injury than other females and people 60 and older. Future research is warranted to investigate temperature injury among different groups of people and the causes of injury.