BLUNN CREEK DELTA. EDUCATIONAL PACKET for TEACHERS

Transcription

1 BLUNN CREEK DELTA EDUCATIONAL PACKET for TEACHERS i

2 BLUNN CREEK DELTA A Project of The Trail Foundation P.O. Box 5195 Austin, Texas Our mission is to protect and enhance the Ann and Roy Butler Hike-and-Bike Trail at Lady Bird Lake. The Blunn Creek Delta project was funded by 3M and administered by The Trail Foundation. Blunn Creek Delta: Educational Packet for Teachers was created under a contract between The Trail Foundation and Environmental Survey Consulting, Austin, Texas. Text and Layout Design Judy Walther, Environmental Survey Consulting 4602 Placid Place, Austin, Texas Original Artwork Susan Denneny, Environmental Survey Consulting Technical Layout Assistance David Timmons David Timmons Design July 2014

3 INTRODUCTION This educational packet is for teachers who might want to include Blunn Creek Delta as part of their curriculum. Included in the packet is background information about Blunn Creek, the formation of the delta, and information about the vegetation and their habitats. In addition to reading material, there are activities for students, including a teacher s copy with potential answers. The delta is located where Blunn Creek enters Lady Bird Lake in Austin, Texas. Visitors can access this location by walking on the Ann and Roy Butler Hike-and-Bike Trail. For information about the trail, visit The Trail Foundation website at: iii

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5 TABLE OF CONTENTS Parts of a Creek 1 What is a Drainage Basin? 2 Cross Section of a Creek 2 Length and Shape of Blunn Creek 3 Elevation 3 Map of Blunn Creek Drainage Basin 4 What is a Delta? 5 Sediment is suspended then deposited 5 How do deltas change over time? 5 Evolution of the Blunn Creek Delta from Aerial Photographs aerial photograph aerial photograph aerial photograph aerial photograph 9 Non-native Plant Invasion 10 Elephant Ear (Colocasia esculenta) 10 Yellow Flag Iris (Iris pseudacorus) 11 What is a non-native invasive plant? 12 How do you control invasives? 12 v

6 Native Habitat 13 Aquatic Plants 13 Blueflag Iris (Iris virginica) 14 Carolina Fanwort (Cabomba caroliniana) 14 Creeping Burhead (Echinodorus cordifolius) 15 Emory Sedge (Carex emoryi) 15 Obedient Plant (Physostegia correllii) 16 Pickerel Weed (Pontederia cordata) 16 Water-Pennywort (Hydrocotyle sp.) 17 Wooly Rose Mallow (Hibiscus lasiocarpos) 17 Upland Grasses 18 Canada Wild Rye (Elymus Canadensis) 19 Eastern Gamagrass (Tripsacum dactyloides) 19 Jamaican Sawgrass (Cladium mariscus spp. jamaicense) 20 Switchgrass (Panicum virgatum) 20 Upland Wildflowers 21 Cardinal Flower (Lobelia cardinalis) 22 Common Goldenrod (Solidago canadensis) 22 Common Sunflower (Helianthus annuus) 23 Woodland 24 vi

7 BLUNN CREEK DRAINAGE BASIN A creek starts at its headwaters, flows downstream and ends at a larger body of water (usually a river). Where a creek ends is called the mouth. Any water coming into the creek from the sides are called side drainages. PARTS OF A CREEK 1

8 WHAT IS A DRAINAGE BASIN? A drainage basin is the entire area collecting rainwater into a creek. The outer rim of the basin connects high points surrounding the creek. Any raindrop falling within the outer rim flows downhill into the creek. Raindrops falling outside the outer rim flow into a different creek. All raindrops that fall inside the high points will flow downhill into the creek bottom, which is the lowest point. All raindrops that fall outside the high points will flow to the creek next door. 2

9 LENGTH AND SHAPE OF BLUNN CREEK Blunn Creek is about 3 miles long, with several small side drainages. At the headwaters near E. Ben White Blvd the land is flat and wide. North towards Lady Bird Lake, the land is steeper along the banks. You can tell if the land is flat or steep depending on how close the contour lines are. (See Activity 3.) ELEVATION Elevation of the creek bed is about 670' at its headwaters and 420' at its mouth. Elevation is shown as contour lines. A contour line follows an elevation and is always level. A contour line at elevation 420 will never be below 420' or above 420'. Elevation is measured starting at sea level. Blunn Creek ranges from 420' to 670' above sea level. 3

10 MAP OF BLUNN CREEK DRAINAGE BASIN 4

11 WHAT IS A DELTA? A delta is a silty shallow area at the mouth of a creek or river, where new land is created by sediment deposits. Since 1960, a delta has formed where Blunn Creek meets Lady Bird Lake. Sediment is suspended then deposited. As rain water travels across Blunn Creek s watershed, it picks up loose dirt (sediment) and carries it downstream. Where the creek enters the lake, its water slows down. Sediment, which is heavier than water, drops to the bottom. Over time, this sediment piles up and spreads into the lake. How do deltas change over time? What happens upstream along a creek can change the delta downstream. If the creek is unstable and carries a lot of sediment from erosion, then the delta will change shape as that sediment is deposited. The following graphics show how the Blunn Creek delta has changed over time. All of these graphics were taken from aerial photographs, starting in 1952 and ending with the current 2014 aerial photograph. Notice how much the delta has changed since Longhorn Dam was constructed in

12 EVOLUTION OF THE BLUNN CREEK DELTA from aerial photographs Before Longhorn Dam: From a 1952 aerial photograph Before the dam, the wild Colorado River changed a lot during big floods. Before construction of Longhorn Dam in 1960, the Colorado River raged through Austin during floods, shifting sediment deposits and sandbars. During the 1930 s, major floods left thousands homeless, destroying dams, bridges, and livestock. In a 1935 flood, Congress Avenue Bridge was under water and flood water even reached the steps of the Capitol. In 1952 Blunn Creek flowed about 75 feet past the unpaved Riverside Drive before depositing sediment into shallow water at the river. 6

13 Town Lake: From a 1966 aerial photograph In 1960, Longhorn Dam was constructed to create Town Lake. Longhorn Dam created the last of the 7 Highland Lakes along the Colorado River. The upper six were constructed in the 1930s and 1940s by LCRA for flood control. Town Lake, built by the City of Austin, was used as a cooling pond for Seaholm and Holly Street Power Plants, as well as for public enjoyment. The dam turned the river into a lake. Sediment pulled out of the river was put along the banks to create new land. In 1966 Blunn Creek flowed about 125 feet from Riverside Drive to the new parking lot, then deposited sediment into a shallow water area about 150 feet long. 7

14 Extension of New Land: From a 2002 aerial photograph New land continued to form as sediment from Blunn Creek built up in the delta. Vegetation sprouted and grew as sediment piled higher than the lake. New land became stable, with deposits creating more sandbars, including a new island at the mouth of Blunn Creek. The delta began to reach beyond the parking lot and restaurant. In 2002 Blunn Creek flowed over 400 feet from Riverside Drive, along old and new land before going northwest past the new island. 8

15 What is the Future? : From a 2014 aerial photograph Nature never stands still. There is always change. In Blunn Creek delta, large storms could blow out sandbars, creating openings for water to flow. A fast-moving creek could eat out the island s bank, causing the island to collapse. Deep-rooted trees are strong and will slow down any change. But changes will happen over time, whether building up, tearing down, or shifting the delta s drainage patterns. In 2014 Blunn Creek flowed about 450 feet from Riverside Drive, going on both sides of the island, to deposit sediment where the creek enters the lake. 9

16 NON-NATIVE PLANT INVASION Non-native plants have been invading the area in and around Blunn Creek delta for many years. At Blunn Creek delta, the dominant non-native is elephant ear, an aggressive native of Southeast Asia. Another non-native invasive wetland plant is yellowflag iris. Elephant Ear (Colocasia esculenta) Family: Arum (Araceae) Plant Type: Semi-aquatic, emergent Nativity: Non-native Habitat: Non-native plant from Asia. Grows in colonies along shorelines of lakes and rivers. Wildlife Value: This plant has little wildlife value. Is invasive and tends to push out native vegetation. 10

17 Yellow flag Iris (Iris pseudacorus) Family: Iris (Iridaceae) Plant Type: Aquatic, emergent Nativity: Non-native Habitat: Non-native plant from Europe, N. Africa and Asia. Grows near water, in wet meadows, forest wetlands, marshes, and along the banks of rivers and lakes. Wildlife Value: This plant has little wildlife value. Is invasive and tends to push out native vegetation. 11

18 WHAT IS A NON-NATIVE INVASIVE PLANT? A non-native plant originates in a different area or country. It s invasive if it out-competes our native plants. Invasive non-native plants tend to reproduce abundantly, out-compete other plants, adapt to many conditions, and are not affected by native diseases. They dominate and change the native habitat. They are not susceptible to checks and balances controlling native species, thus disrupting natural ecology and causing a decline in healthy diversity. HOW DO YOU CONTROL INVASIVES? Measures have been taken to manage non-native species at Blunn Creek delta. Removal techniques include hand removal and careful herbicide treatment. Experimental areas have been set up to monitor management strategies. During the Blunn Creek delta project, results were shared with The Trail Foundation and City of Austin. 12

19 NATIVE HABITAT After removing non-native, invasive plants in Blunn Creek delta, a diversity of native plants was planted. Native plants support native insects, reptiles, birds and mammals, who suffer when non-native plants are dominant. Native animals and plants have evolved an interdependent web of life. In addition to creating healthy ecosystems, native plants reinforce a sense of identity and pride in our natural heritage. AQUATIC PLANTS Aquatic plants grow under water, partially emerging or at water s edge in marshy areas. Aquatic species have specific needs. Submerged plants grow entirely under the water. Emergent plants grow mostly under water, except for their flower stalks. Edge plants have roots in moist soil, but can t tolerate flooding. Other aquatic plants have no roots, growing in floating mats. Sixteen aquatic species were found during a 2013 plant survey of Blunn Creek delta, including three non-native species. The following drawings are of some of the aquatic plants found and/ or planted in the Blunn Creek delta during the 2013 plant survey and the habitat restoration planting in

20 Blueflag Iris (Iris virginica) Family: Iris (Iridaceae) Plant Type: Aquatic, emergent Nativity: Native Habitat: Usually grows at the edge of permanent water, sometimes in dense colonies. Likes it when the ground dries out in spring and summer. Wildlife Value: Has little wildlife value, except Nutria like to eat the basal parts of the plants. Hummingbirds and other pollinators enjoy blueflag iris. Carolina Fanwort (Cabomba caroliniana) Family: Water-Shield (Cabombaceae) Plant Type: Aquatic, submergent Nativity: Native Habitat: Grows in slow moving creeks, rivers, ponds and ditches. Can spread and be a nuisance to boaters and fishers. On a positive note, it can take up unwanted extra nutrients and provide oxygen. Wildlife Value: Some ducks and other water fowl like to eat Carolina fanwort. Not much value for other wildlife except as a place for fish, frogs and some invertebrates to hide. 14

21 Creeping Burhead (Echinodorus cordifolius) Family: Water-Plantain (Alismataceae) Plant Type: Aquatic, emergent Nativity: Native Habitat: This plant is found in swamps, marshes and ditches and spreads by creeping above ground and rooting at the tips or nodes. Wildlife Value: Has little wildlife value, except Nutria like to eat the basal parts of the plants. It provides cover for small animals. Emory Sedge (Carex emoryi) Family: Sedge (Cyperaceae) Plant Type: Aquatic, emergent Nativity: Native Habitat: Grows along banks of creeks and in marshy areas that dry out in spring and summer. Wildlife Value: Seeds are eaten by many shorebirds, rodents and small mammals. Leaves are eaten by small mammals. Good hiding place for birds. Host for some butterfly larva. 15

22 Obedient Plant (Physostegia correllii) Family: Mint (Lamiaceae) Plant Type: Aquatic, emergent Nativity: Native Habitat: Rare plant that grows along river banks and marshy areas. Spreads underground and can form dense colonies. Wildlife Value: Pollinated by bees. Not much wildlife value except as a cover for birds and small mammals. Pickerelweed (Pontederia cordata) Family: Pickerelweed (Pontederiaceae) Plant Type: Aquatic, emergent Nativity: Native Habitat: Found in marshes, swamps, and slow-moving water along rivers in shallow water up to about one foot deep. Can form large sprawling colonies. Wildlife Value: The nectar and pollen attract butterflies and bees. Also food for other insects. Seeds eaten by water fowl. The dense colonies provide cover for fish and other aquatic animals. 16

23 Water-Pennywort (Hydrocotyle sp.) Family: Carrot (Apiaceae) Plant Type: Aquatic, emergent Nativity: Native Habitat: Found in marshes and at the banks of creeks, ponds and lakes. Can form large mats. Spreads by above-ground runners, rooting at the nodes. Wildlife Value: The fruit is eaten by birds. Otherwise, not much wildlife value. Fish can hide in the large mats. Wooly Rose-Mallow (Hibiscus lasiocarpos) Family: Mallow (Malvaceae) Plant Type: Wildflower Nativity: Native Habitat: Grows in marshes and swamps, but where the soil can dry out during summer. Also found in wet pastures, ridges next to permanent water and along riverbanks. Wildlife Value: Seeds are eaten by small birds and sometimes by ducks. Pollinated by bees. 17

24 UPLAND GRASSES Upland areas near water support grasses and wildflowers that need both extra water and soils that periodically dry out. Grasses and grass-like plants that grow near water have either deep root systems or densely matted shallow roots, both of which are good for erosion control. Deep-rooted grasses are workhorses, holding riverbanks through flood events and removing unwanted nutrients from water and soil. Quick-growing grasses with shallow, matted roots are also excellent for erosion control. Six grass species were found during a 2013 plant survey of Blunn Creek delta, including two non-native species. The following drawings are a few of the grasses and grass-like plants found and/or planted in the Blunn Creek delta during the 2013 plant survey and the habitat restoration planting in

25 Canada Wild Rye (Elymus Canadensis) Family: Grass (Poaceae) Plant Type: Grass Nativity: Native Habitat: Often found in shady riparian wetlands, on the banks of creeks and rivers. Can also be found in prairies. Wildlife Value: Seeds are eaten by many birds and small animals. Provides nesting areas and other cover for birds and small animals. Eastern Gamagrass (Tripsacum dactyloides) Family: Grass (Poaceae) Plant Type: Grass Nativity: Native Habitat: Deep-rooted plant that grows in marshes, swamps, and banks of creeks. Can also be found in prairies. Wildlife Value: Larval host plant for some butterflies. Seeds are eaten by birds and deer. Provides good cover for birds and small animals. Large animals like to graze on this plant. 19

26 Jamaican Sawgrass (Cladium mariscus spp. jamaicense) Family: Sedge (Cyperaceae) Plant Type: Grass-like Nativity: Native Habitat: Grows in marshes and along creeks, ponds, lakes and other wetlands. Wildlife Value: Nutria like to eat the soft starchy roots. Seeds are sometimes eaten by water fowl. Provides good hiding cover for ducks and small mammals. Switchgrass (Panicum virgatum) Family: Grass (Poaceae) Plant Type: Grass Nativity: Native Habitat: An upland variety is found in prairies. A lowland variety is found in marshes, wet meadows and along lakeshores and is tolerant of some flooding. Deep roots are good for erosion control. Wildlife Value: The seeds provide food for many birds. It also provides nesting and cover for birds and small animals. 20

27 UPLAND WILDFLOWERS Upland wildflowers at Blunn Creek delta are either quick-growing plants in new sunny areas or shade-tolerant species under trees. Open, newly established land is a place for sun-loving, early succession vegetation. These stabilizing pioneer plants grow rapidly, often annuals with lots of seeds and weak root systems. With a habitat s maturity come slower-growing, more stable perennial plants. Nine native wildflower species were found during a 2013 plant survey of Blunn Creek delta. The following drawings are a few of the wildflowers found and/or planted in the Blunn Creek delta during the 2013 plant survey and the habitat restoration planting in

28 Cardinal Flower (Lobelia cardinalis) Family: Bellflower (Campanulaceae) Plant Type: Wildflower Nativity: Native Habitat: Grows in wet prairies, swales, floodplains, soggy meadows and along rivers and creeks. Wildlife Value: The nectar attracts hummingbirds and various bees and butterflies. Otherwise, there is little wildlife value, due to the toxic latex in the leaves. Common Goldenrod (Solidago canadensis) Family: Sunflower (Asteraceae) Plant Type: Wildflower Nativity: Native Habitat: Found in upland prairies as well as in damp meadows and along stream banks. Wildlife Value: Nectar and pollen for bees, butterflies and other insects. 22

29 Common Sunflower (Helianthus annuus) Family: Sunflower (Asteraceae) Plant Type: Wildflower Nativity: Native Habitat: Found in open areas and in roadside ditches. Can tolerate extra moisture as long as the soil dries out periodically. Wildlife Value: A high wildlife value. Pollen and nectar attracts insects. Birds eat the seeds and oil. Their tall stalks provide shade and shelter for ground animals. Deer like to browse the leaves and seeds. Provides cover for many birds and small animals. 23

30 WOODLAND Since 1960, woody plants took root as new land was formed, expanding into the current woodlands. Tree roots hold soil, creating stable habitat. Older trees are located furthest away from the shoreline, since they ve been there longest. The island started formation about 2002 and has the youngest woodland. There is a moderate woodland diversity in the delta. Twentysix trees, shrubs and woody vines were found during a 2013 plant survey of Blunn Creek delta, including seven non-native species. 24