Browsing by Subject "Watershed management"
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Item Eastern watershed analysis of alternate approaches to delineation in Austin, TX(2010-05) Vermillion, Elizabeth Lauren, 1982-; Paterson, Robert G.; Schuster, StefanDrainage area is a measure of the number of acres feeding into a creek. Drainage area threshold is the amount of acreage required for the creek to be included on a map. Watersheds mapped according to higher drainage area thresholds will show creek systems that are shorter and concentrated at the bottom of the watershed. Watersheds mapped according to lower drainage area thresholds show creek systems that are longer and extend further up the watershed. Since all watersheds are subject to different land uses, soil types, geology, etc., they should be mapped according to different drainage area thresholds. Headwaters are where creeks begin. There is empirical evidence that properly functioning headwaters significantly reduce erosion, improve water quality, slow stormwater flows, and provide habitat. If municipalities use lower drainage area thresholds to define their creeks, they can include more headwaters in their creek setback requirements. This professional report identifies the Harris Branch watershed as being under relatively more pressure to develop and exhibiting more environmental risk than other watersheds in Austin, Texas’ Desired Development Zone. Creeks in the watershed are redrawn according to reduced drainage area thresholds using a simple ArcGIS analysis. The analysis reveals a critical mass where creek setbacks appear to be too extensive. If creeks with a drainage area of 5 acres are protected by development code, the setbacks created have excessive branching that could be too restrictive for development. A critical mass ratio should be considered when determining which drainage area threshold is most appropriate for a watershed. The critical mass ratio is equal to the number of branches allowed per a specified distance of creek centerline. The process of identifying this critical mass ratio can help growing cities find a balance between the need to encourage development in designated areas and the need to protect natural creek systems everywhere. I recommend that municipalities review the effects of reducing drainage area threshold for each watershed, and then identify the drainage area threshold that, when protected by setback requirements, allows for extended and connected greenways as well as an increase in density.Item The impact of the comprehensive watersheds ordinance on stream health in Austin, Texas(2016-08) Kip, Nathalie Carmen; Paterson, Robert G.; Sletto, BjornWhile Austin is often considered a leader in water quality management, it still has streams which are impaired. As urban development occurred in Austin, there appears to have been a diminishing regard for these creeks. As Austin receives the majority of its drinking-water supply from the Colorado River (a surface water source), there is a critical need to increase our understanding of the relationship between development trends and water quality in order to continue the implementation of successful watershed planning strategies and regulations. Further, there is a need for the evaluation of watershed protection regulations that have already been established, in order to determine their success. This thesis presents data from an analysis of water quality of creeks in watersheds that were primarily developed prior to the passing of Austin’s first Comprehensive Watershed Ordinance (CWO) in 1986, compared to water quality of creeks in watersheds that were primarily developed after the Ordinance was adopted. This exploratory study investigated the following research questions: How does stream health differ between watersheds that were primarily developed prior to the passing of the CWO compared to those that were mostly developed after the CWO? How do impervious cover, watershed size, soil type and watershed development affect stream health outcomes (metals, nutrients, macroinvertebrate biodiversity and water temperature) in the creeks under study and what are their empirical relationships? A total of forty-eight creeks were studied. Analysis included both GIS mapping and statistical methods. Three of the primary best management practices established by the CWO included riparian buffers, impervious cover regulations, and density controls. The findings reveal that post-CWO creeks have better stream health outcomes for lead, chromium, and nitrate concentrations. Water temperatures are generally lower in post-CWO creeks. Additionally, these creeks have greater macroinvertebrate biodiversity. Therefore, this study confirms that Austin’s watershed regulations do matter as they have had a positive impact on stream health in the city. The city should continue to focus on best management practices that will result in living streams, including: increasing riparian canopy cover throughout the city, promoting the development of rain gardens, establishing incentives for the use of impervious surface alternatives such as permeable pavers, and finally continue to educate and engage with Austinites regarding the protection of the city’s water network.