How can I narrow down a broad topic on sustainable urban planning for my senior capstone thesis?

To narrow down a broad topic like sustainable urban planning, it's essential to balance academic rigor with manageability. Your advisor's feedback suggests that city-wide policy is too vast, but a case study might be too narrow. A potential middle ground is to focus on a specific aspect of green infrastructure within a particular urban context. For instance, you could investigate how urban green spaces impact air quality in a city with high levels of pollution, or explore the economic benefits of green roofs in a district with a high concentration of commercial properties. Consider using a geographic information system (GIS) to analyze and visualize data related to your chosen aspect of green infrastructure. This can help you identify trends and patterns that might not be immediately apparent from a general overview of the data. You can also use GIS to narrow down your case study to a specific neighborhood or district, which can make the data more manageable and provide a more nuanced understanding of the issue. Another approach is to frame your case study within a specific theoretical or conceptual framework, such as the concept of "green infrastructure" itself, or the "urban metabolism" theory. This can provide a clear structure and direction for your research, and help you to identify key variables and relationships that are relevant to your chosen aspect of green infrastructure. By combining a specific case study with a clear theoretical framework, you can create a compelling and well-structured argument that meets the academic rigor your professor expects.