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Seminar_EWRE
- 2. Client: New Braunfels Utilities (NBU) Project: Greyfield development Consultants: EDG, Ten Eyck, Lake Flato
- 4. BLIEDERS CREEK COMAL RIVER SPRING HEAD NBU PROPERTY
- 6. Site Assessment NRCS Web Soil Survey Site Inspection
- 7. 0 100 200 300 400 500 1931 1941 1951 1961 1971 1981 1991 2001 2011 MeanAnnual Discharge(cfs) Comal River Discharge -20 -15 -10 -5 0 2000 2001 2002 2003 2004 2005 2006 Depth(feet) Groundwater levels near NBU site 0 200 400 600 800 1/1981 1/1987 1/1993 1/1999 1/2005 1/2011 Precipitation (mm) Monthly Precipitation Estimates Hydrologic Data
- 8. Location Measured (in/hr) Measured (μm/s) Oakalla Silty Clay Loam (μm/s) Point 1 0.240 1.693 9.0 Point 2 0.216 1.524 9.0 Point 3 0.106 0.748 9.0 Saturated Hydraulic Conductivity
- 10. Restoration Goals Protecting the spring Stormwater Flood impacts Restoring the spring Increasing infiltration Using stormwater
- 12. Stormwater Management Reducing surface runoff Rainwater harvesting, Vegetative buffer zones Redirecting runoff away from the spring head Flow splitters, Pool and riffle systems Treating surface runoff Bioswales, Checkdams
- 13. Rainwater Harvesting 0.00 1.00 2.00 3.00 4.00 5.00 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Rainfall(inches) New Braunfels Rainfall: Monthly Medians
- 14. Rainwater Harvesting Runoff volume = Roof area X Rainfall depth X Curve number Building Roof Area (sq. feet) Runoff (gallons) Cistern Size (gallons) Flex Space 9,600 158,486 52,829 Historic Building 1 3,744 61,810 20,603 Historic Building 2 1,680 27,735 9,245 Main Complex 21,440 353,952 117,984 Community Halls 7,584 125,204 41,735 Totals 44,048 727,187 242,396
- 17. Acknowledgements Prof. Howard Liljestrand Dr. Mark Simmons (Director, EDG) Emily Manderson, Julia Raish, Darcy Anders (EDG)
Editor's Notes
- Did an internship last fall with the Ecosystem Design Group at the Wildflower Center; Group includes landscape architects, conservationists, ecologists, environmental designers, and they work as environmental consultants; specialize in ecological/restoration design.One of their projects was in New Braunfels. NB is in Comal county in Texas.
- The client wanted to generate ideas for green development. They wanted the place to be an educational cum recreational space, where locals could learn about the significance of the springs, the ecosystem it supports, stormwater pollution, using native plants, etc. Basically they wanted ideas for what the site could be converted into and EDG was responsible for the initial/preliminary site assessment and planning.
- Comal Springs concerns: endangered species, minimum flow requirements,runoff pollution, excessive abstraction
- This is an aerial view of the project site; Show North; the property was built several decades ago and lies upstream of Comal River and Landa Lake (therefore any adverse runoff had the potential to impact these water bodies); It is bounded on the North-West by the Balcones Escarpment – hence the site lies on the eastern boundary of Texas Hill country and on the Western boundary of the Texas Coastal Plain; Blieders creek flows on the southern side of the property; one of the spring heads of the Comal springs system adjoins the site.Most of the site is covered with concrete and is therefore impervious. Overall, from a hydrology point of view, this is a very interesting and perhaps unique location!
- Above left shows stream near main spring, image on lower left is the capped spring head adjoining the site, lower right shows the confluence of Blieders creek and the head of Comal River.
- As part of site assessment, we collected information on soil type (NRCS Web Soil Survey), plants and aquatic species, collected historic aerial imagery, conducted a site visit, collected data on saturated hydraulic conductivity of site soil by using an Amoozemeter (Compact Constant Head Permeameter). Also looked at similar sites elsewhere, like the Aquarena site in San Marcos. Also visited the Cibolo Nature Center in Boerne to get ideas for this site.
- [Can put FEMA floodplain map on this slide. Say that significant portion of the site lies within the 100-yr floodplain. Can also show Ksat values and say that they are less than expected for the soil type on the site, which probably indicates soil compaction.]Here, we can see some hydrological data for the area around site. The discharge data for Comal River is at a location downstream of Landa Lake. Comal Springs are perennial in nature and the only period when the springs stopped flowing was during June to November, 1956. This happened due to excessive drop in the levels of the Edwards aquifer. Groundwater elevations shown are elevations are nearby sites and one can see that the in general the water table in this area is not very deep. Groundwater data is from TWDB.Monthly precipitation estimates are from the PRISM precipitation model. The average monthly precipitation over the last 30 years is [], and the maximum rainfall occurs during the months of [].
- I was involved in measurement of saturated hydraulic conductivity at the site. Ksat is a measure of the ease with which saturated soil transmits water.
- Here’s a map showing the elevations around the site. The rise in elevation across the escarpment can be seen. Also, one can see that the lowest elevations are along Blieders creek and Comal river. The main thing to note is that in a rain event, stormwater flows over the property would probably occur in a North-East to South-West direction. Also, the site is flooded by Blieders Creek from the North end.
- Protecting the spring head from stormwater pollutionProtecting the spring from pollution during flood events, mitigating flood impactsIncreasing site contribution to aquifer rechargeReducing groundwater withdrawals and using stormwater/greywater for landscape irrigation purposes
- Flood Impact Mitigation – I found that the City of New Braunfels is already considering drainage improvements for Blieders Creek.This map is from a hydraulic study done by HMT engineers, where they propose diverting floodwater away from Blieders creek to nearby German creek. They even propose re-routing floodwaters directly to Comal River. No plan has been approved as of now.
- Bioswales are depressed/shallow landscape elements designed to remove silt and contaminants from surface runoff water.Checkdams are small dams built in a drainage channel or swale. They are a water quality control measure.Their purpose is to reduce channel erosion, slow down stormwater runoff and allow sediments and pollutants to settle.
- To get a cistern size estimate, we need to calculate expected roof runoff. This can be done by using special maps, such as this one published by the Texas Water Development Board (TWDB). Once you choose your location on this map, you can get a range limits for the average annual runoff from a 2000 sq. ft. roof. The other way is to calculate the roof area at your site and multiply that by the median monthly rainfall values at your site to get expected runoff for each month.Using monthly median rainfall data is a more conservative method, and is likely to provide a higher reliability than using average rainfall data for system sizing.
- Water demand estimates for various buildings were not known; hence used rule-of-thumb for calculating cistern sizes; Curve number used in calculations in 0.95 (to get a conservative estimate).