The Water Quality section of Austin’s Land Development Code designates the most sensitive portions of watersheds as critical water quality zones, often including flood plains and other areas closest to streams and lakes. In all watersheds, development in critical water quality zones is limited to parks, golf courses and open space or water-related uses, such as docks and marinas, in selected areas. Adjacent to the critical water quality zone, a water quality transition zone extends outward another 100, 200 or 300 feet depending on whether the waterway is considered minor, intermediate or major. In a water quality transition zone, maximum impervious cover limits vary depending on the sensitivity of the watershed, ranging from 18 to 30 percent impervious cover. Land outside of critical water quality zones and transition zones are considered uplands. Again, depending on the sensitivity of the watershed, impervious cover limits can range from 30 percent to 65 percent and can increase as detailed below when coverage rights are transferred. Transfers are not allowed in the Barton Springs Zone but can occur in three other watershed categories: Suburban Watershed, Water Supply Suburban Watershed and Water Supply Rural Watershed.
In areas defined as Suburban Watersheds, 20,000 square feet of impervious cover can be transferred to an uplands zone for each acre of land in critical water quality zones that are dedicated to the city. Similarly 20,000 square feet of impervious cover can be transferred for each acre left undeveloped in a water quality transition zone, for each acre of land preserved in the buffer area for a critical environmental feature and for each acre of upland land used for wastewater irrigation and restricted against future development. Furthermore, 17,000 square feet of cover can be transferred per acre of land restored with native plants and used as a golf course or some other recreational facility and 10,000 square feet can be transferred for each acre of land in a water quality transitional zone used for wastewater disposal. The receiving tract must be within one mile of the transferring tract. Finally, the applicant must concurrently plat the transferring and receiving tracts and must transfer all development intensity at that time.
In another land category named Water Supply Suburban Watersheds, impervious cover is more limited than in the Suburban Watershed category described above. The transferable coverage per acre of sending area land is lower than in the Suburban Watershed category. Likewise the maximum cover achievable with TDR is lower: for single-family development, coverage can increase from 30 to 40 percent; and for commercial or multiple family residential, cover can increase from 40 to 55 percent. However, the restrictions on transfer distance and concurrent platting or sending and receiving areas is similar to those found in the Suburban Watershed category.
In another category named Water Supply Rural Watersheds, the receiving areas in the Uplands Zones can go from one unit per two acres to one unit per acre for single-family residential uses that use TDR and from one unit per acre to two units per acre for clustered housing that uses TDR. For commercial or multiple family residential development, TDR can be used to increase cover from 20 to 25 percent. The amount of development intensity that can be transferred is different from that allowed per acre preserved in the Suburban Watershed or the Water Supply Suburban Watershed categories.
Pat Murphy of the City of Austin reported in April 2005 that these transfer provisions had been used many times but that the City had not attempted a formal inventory of the land preserved as a result. He also mentioned that preservation occurred on a case-by-case basis in the Barton Springs Zone even though the formal transfer mechanism does not apply in that zone.
