Land Use Impacts

Land conversion and construction practices across Hawai‘i have a significant impact on the environment, including water quality, air quality and soil erosion. Mitigating the effects of these impacts can conversely create more livable communities and generate a healthier, better quality of life. An important component of this target is to track progress toward reducing impacts on natural ecosystems by focusing new development in the existing urban zone. This will measure increases in urban density and subsequent reduction in land conversion of green spaces and agricultural land, while enhancing livability within urban areas and urban clusters. There are two classifications under the US Census Bureau for urban land: urbanized areas and urban clusters. Urbanized areas are well understood by most, and are defined as lands zoned as “urban” with populations above 50,000 people. The 3 urbanized areas in the state are Kailua (Honolulu County), Kahului (Maui County), and Urban Honolulu which stretches from Hawai‘i Kai to Makaha (DBEDT). Urban clusters, including Kalaheo on Kaua‘i and Captain Cook on Hawai‘i Island, are defined as population centers over 2,500 but less than 50,000, and also are accounted for under the urban land zone (DBEDT). Some of the gaps and opportunities in land use relate to the key role of planning and permitting.

Following general trends of population increase in Hawaii, urban density is measured to track where this population is residing. This is not to encourage an increase in population, but to encourage densification rather than sprawl. Urban density is balanced by tracking park acreage per capita in the Open, Public, and Green Spaces target to show that urban areas maintain green spaces which contribute to increased health and livability in urban areas.

Urban density is a common tool used by planning practitioners and researchers for gauging regional land use patterns. By tracking the statewide population compared to the total acres designated under the urban districts by the state Land Use Commission, urban density can be tracked over time based on changes in both population and urban land acreage, which includes both urbanized areas and urban clusters.

Figure 1: The bar graph expresses urban density by showing the statewide proportion of people per acre of land designated as urban (both urbanized areas and urban clusters). 

Source: Department of Business, Economic Development and Tourism (DBEDT) and University of Hawai‘i Economic Research Organization (UHERO)

Figure 2: The line graph shows the year to year percentage change in residential population statewide. The data can be used as a reference point for urban density increases over the same time period. Based on this data, the major increases in population density over the past 15 years do not correlate with percentage increases in population, which reflects a gradual year to year increase during this time frame.

Source: University of Hawaiʻi Economic Research Organization (UHERO) and Department of Business, Economic Development & Toursim (DBEDT)

Land use has a major impact on water sources across the state, primarily through changes in land cover. Development patterns and design choices impacting land cover include levels of impervious surface, impacting sedimentation rates and non-point source pollution. Strategies to mitigate theses negative impacts often include low impact development and green infrastructure, such as bioswales, rain catchments, urban forestry and permeable pavement. Land use impacts on water quality has a direct connection to overall health for communities as well. By mitigating water pollution from non-point source run off affecting streams and marine conditions, communities can address health concerns to improve wellbeing and quality of life for everyone.

Figure 3: The bar graph illustrates the total number of Brown Water Days as reported by the Department Health as public advisories indicating water quality could be harmful to personal health. Various factors could can cause brown water advisories and typically result from water runoff into streams and ocean bodies.

Source: Department of Health

Figure 4: Water Monitoring Locations (Source: Department of Health)

Figure 5-9: These maps highlights the water quality standards for both streams and near-shore ocean water based on Department of Health indicators per island. Source: Department of Health--Clean Energy Branch

Healthy streamflow and base flow (groundwater discharge to streams) in Hawai'i are critical elements of the water cycle. Streamflow recharges groundwater which maintains thriving ecosystems and drinking water, and baseflow is the groundwater contribution to stream flow. In the past century, there has been a decrease in both streamflow and baseflow by over 20%. This shift may affect long-term climate change and land-cover factors.

Figure 10: Trends in streamflow in Hawaii, 1913-2008. Trendlines shown in a solid line indicate a significant decrease while dashed trendlines are less significant.Source: US Geological Survey

Figure 11: Trends in baseflow in Hawaii, 1913-2008. Trendlines shown in a solid line indicate a significant decrease while dashed trendlines are less significant. Source: US Geological Survey

Figure 12: Map of real-time streamflow compared to historical streamflow for the day of the year (Hawaii) Source: USGS

Continued development causes an increase in impervious surfaces across the state of Hawaii. This inhibits the ability for watershed run-off to be absorbed into groundwater and increases non-point source pollution run-off and the urban heat island effect. 

Impervious surfaces across Hawaii are captured in the map below in shades of pink. Note that the source data did not provide a legend.

Figure 13: Impervious surfaces across Hawaii; Source: USGS The National Map (nationalmap.gov)

Source: Department of Business, Economic Development and Tourism (DBEDT)

The map to the right displays the land use districts and boundaries across the Hawaiian Islands. Users can zoom in closely to the interactive map to view State Land Use Districts ranging from agriculture, conservation, rural, and urban areas within each county.

Source: State Land Use District