Secondary and Cumulative Impacts Master Management Plan - 2014

SECTION 4 – DESCRIPTION OF EXISTING ENVIRONMENT IN PLANNING AREA

TABLE 4-2 Planning Area Detailed Existing Land Use

Estimated Impervious Square Miles

Percent of Planning Area

Estimated Percent Impervious 4

Land Use Type

Square Miles

Commercial

0.6 1.0 1.0 0.2 1.2 0.8 0.7 1.4 1.9 0.3 0.7 9.8

6%

82% 82% 72% 72% 87% 72% 44% 21%

0.5 0.8 0.7 1.1 0.6 0.3 0.3 0.1

Industrial

10% 10%

Office and Institutional

2%

Mixed Use 1

13%

Transportation 2

High-density Residential Medium-density Residential Low-density Residential

8% 8%

14% 19%

4% 4% 4%

<0.1 <0.1

Undeveloped/Vacant 3

Golf Course

3% 7%

Park/Greenway/Open Space

0.5 4.5

Total

100%

Sources: Town of Morrisville, 2013 Note: The Town’s land use categories are described in Appendix D

1 Mixed use was categorized within the non-residential developed category in Table 4-1. 2 Transportation is not included in the land use coverages. The area used for transportation was estimated by subtracting the land use area from the transportation area. 3 Undeveloped land is forested or vacant lots. The Town does not have any active farms. 4 Percent imperviousness estimates are based on a modeling analysis done for the Town of Cary (CH2M HILL, 2002a). Imperviousness values most likely over-estimate the percent imperviousness because reference categories contained slightly higher densities for residential classes than the Town of Morrisville designates. Table 4-2 also includes estimates of percent imperviousness; the estimated values shown in the table were used in modeling analyses performed for the Town of Cary in its Northwest Area (CH2M HILL, 2002a). These values are based on literature values. The percentage impervious per land class was used to estimate the impervious area for the 2013 land use data. These were then summed and divided by the total land area to estimate the overall impervious value for existing land use conditions. The total estimated percent impervious is approximately 45 percent. 4.4 Wetlands For regulatory purposes under the Clean Water Act (CWA), the term wetlands means “those areas that are inundated or saturated by surface water or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.” In general, wetlands share three key characteristics: wetland hydrology, hydric soils, and hydrophytic vegetation. Wetlands and vegetated riparian areas are valuable because they are among the

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