Name an essential feature of a modern housing development concerning sanitation.

The inclusion of green spaces for psychological well-being and ecological balance is an essential feature of modern housing developments concerning sanitation. Green spaces, such as parks and gardens, play a critical role in improving the overall quality of life for residents. They provide areas for recreation, promote mental health, and enhance community interactions. Furthermore, green spaces contribute to ecological balance by supporting biodiversity, improving air quality, and managing stormwater runoff, which can mitigate flooding and reduce pollution.

In housing developments, the thoughtful integration of green spaces can also lead to healthier living environments. These areas can serve as natural buffers that filter pollutants and provide habitats for wildlife, thus maintaining a diverse ecosystem even in urban settings. Moreover, access to green spaces has been shown to encourage physical activity, which is beneficial for the residents' physical health.

In contrast, while high-density population, availability of multi-story buildings, and implementation of strict zoning laws may have implications for urban planning and community organization, they do not directly relate to sanitation and the enhancement of living conditions in the same holistic manner as the incorporation of green spaces does.