Upper Walnut Creek Austin's Blog

2011 Survey

There are no no significant changes in the stream or adjacent land from the 2010 survey (below). See the January monitoring post for the photos. The video for the 2011 stream survey is at YouTube

2010 Survey

We did the annual stream survey on January 18, 2010. Per the LCRA’s directions, it is a screening tool used to identify water quality concerns and to learn about stream ecosystems. The goal of the survey is to evaluate changes over time. The preferred time to complete the survey is during the winter when the flow is low and vegetation is minimal.

Here are the results of the stream survey – and one important note: the day we did the survey was 2 days after the area had 2″ of rain. So the stream flow was a bit higher and stronger than we normally have observed (especially after the lengthy drought!).
See the photos below

The major Land Uses

Residential 35%, Forest/Parkland 65%

Land Use – stream side or within 1/4 mile of the stream are

• Residential: – Single & multi family housing, lawns, playground and parking lot
• Commercial/Industrial – a small shopping center, 2 gas stations, roads and a bridge
• Forest/Parkland – Recreational park and woods/greenbelt
• Recreation – Biking/off-road trails and jogging/hiking trail (including through the stream)

Stream Reach Characteristics

The stream habitats include a

• pool which is approx 3-4 ft  deep  (a pool is a deeper area with relatively slow flow). This is where we obtain the sample water as the rest of the stream is too shallow
• riffle (shallow area where water flows swiftly over gravel and rock)
• run which is between 1/2 and 1 ft deep  (a run is a section of stream with relatively high velocity and little or no turbulence on the surface)

Stream channel width/depth: Approx. 20 ft wide – it is always more than 6 ft between the banks – and is shallow. Except for the pool mentioned above, it is less than 1 ft deep.

Average water velocity: 1.4 ft/second. Due to the recent rain this may be a bit faster  than normal.

Substrate type composition: 70% bedrock (solid rock), 20% boulders (greater than 10 inches diameter) 10% cobble (2-10 inches diameter). The boulders and cobble on the stream bottom are mostly embedded (75%) in the silt, sand and mud.

Stream slope: looking downstream, both banks are gradual slopes (less than 30 degrees)

Bank modifications: – where the bank has been artificially covered by rocks, wood or concrete: right bank 60%, left bank 0%

Streamside cover:  both banks contain  trees, bushes/shrubs and native grasses. The left bank also has pavement and a structure – a wooden ramp which reaches the top of the bank, about 20 ft above the stream.

Canopy cover: (pct of stream bank covered in vegetation that has potential to shade the stream – this is a linear measurement of the stream bank)
Right bank 20%, left bank 30% cover

Naturally occurring organic material (leaves, twigs, etc) in stream – none. We’ve never observed more than a twig or 2 in the stream.

Stream conditions:
both banks have natural plant cover degraded and an actively discharging pipe – the left bank’s pipe is approximately 100 ft upstream, just beyond the bridge.

Animals in or around the stream – we’ve seen reptiles (turtles) but no birds, amphibians, livestock or mammals other than dogs who are with their owners in the park.

Fish – small and medium size (up to 6 inches) are often present. Mostly they appear to be minnows.

Aquatic plants – occasional plants are in the stream margin. During the summer there can be fairly extensive algae in and on the stream but now there is none. When present, the algae is green and is normally in clumps. Looking through past photos, there was extensive green algae on the surface and in the water in Feb. 2009.

Structures:  there is a bridge for Metric Blvd (a 4-lane divided road) and a small waterfall just above the sample area. (the waterfall is upstream of the bridge).