Category Archives: GIS

Policy Paradox: Mapping Residential Restrictions

Do residential restrictions placed on convicted sex offenders serve to protect the public?  Duke Economics Ph.D. candidate Songman Kang, has been using the analytical capabilities of geographic information software to help determine the extent to which the restrictions affect residential locations of sex offenders: computing the area covered by a restriction and determining which offenders had to relocate due to a restriction.

According to Kang, the residential restrictions are designed to reduce recidivism among sex offenders and prevent their presence near places where children regularly congregate.  Neither of these claims has been found consistent with empirical evidence though, and it is unclear whether the restrictions have been successful in reducing the rates of repeat sex offenses.  On the other hand, the restrictions severely limit residential location choices, and may force offenders to relocate away from employment opportunities and supportive networks of family and friends.  As a result of the deteriorated economic conditions, the offenders who had to relocate may become more likely to commit non-sex offenses.

The following maps illustrate some of the restricted zones in Miami and in the Triangle area of North Carolina studied by Mr. Kang.

Figure 1: Residential Restricted Zones in Miami

Figure 2: Triangle Restricted Residences

Making Data Flow

As water quality and questions of water supply have grown more salient in the Triangle, Duke researchers have tried to contribute to the growing debate over water quality using the latest digital mapping (GIS) tools.  In the fall of 2009, Data and GIS Services in Perkins Library provided GIS analysis support for a stream and watershed assessment project that developed strategies to reverse the impact of poor urban stormwater management, degraded water quality, and the loss of natural habitats on the Duke campus.

Data/GIS helped the researchers access critical spatial data for the characterization of the contributing watershed’s current land use patterns.  This data enabled the students to analyze the watershed’s area of impervious surface and hydrologic flow paths, and helped inform the understanding of the water quality issues faced at the stream site.

The GIS map below illustrates how digital mapping tools can be used to summarize a large amount of complex data into a compelling presentation.

Special thanks to the interdisciplinary team of environmental and civil engineers, biology and environmental science majors, and a Nicholas MEM student who shared their project results: Alicia Burtner, Matt Ball, Nari Sohn, Avni Patel, Will Bierbower, Adam Nathan, Mike Schallmo, Justine Jackson-Ricketts, and Jai Singh.