06 Briefing - Urban Stream Syndrome.pdf — original pdf

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Urban Stream Syndrome Staryn Wagner Environmental Scientist Senior Staryn.Wagner.austintexas.gov ZAP 12/20/2022 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T  Executive Summary U r b a n S t re a m Sy n d ro m e i s t h e c a s c a d e o f e nv i ro n m e nta l d e g ra d at i o n o f w ate r w ay s re s u l t i n g f ro m d e ve l o p m e nt I m p e r v i o u s c o ve r c a u s e s e ro s i o n , i n c i s i o n a n d l o s s o f h a b i tat t h ro u g h s i g n i f i c a nt c h a n ge s to t h e hyd ro g ra p h b e c a u s e o f : • • • limited infiltration decreasing baseflow rapid runoff increasing stormwater velocity increased volume exacerbating flood frequencies and levels Po l l u ta nt s a n d re d u c e d b i o l o g i c a l c o m p l ex i t y o f t h e l a n d s c a p e a l te r st re a m e c o l o g y b y re d u c i n g d i ve rs i t y a n d re s i l i e n c y C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 2 Stream Functional Pyramid C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 3 Drivers 1. Land use/management 2. Loss of natural vegetation 3. Introduction of non-native species Impervious cover 4. 5. Efficient stormwater system 6. Stream channel modification Increased pollutant load 7. C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 4 Symptoms Increased frequency and severity of flooding Incision/downcutting of channels 1. 2. 3. Disconnected from floodplain and riparian zone 4. Baseflow recession 5. Simplified riffle/run/pool structure 6. Lack of suitable habitat in streams 7. Loss of sensitive flora and fauna 8. Reduced ecological function 9. Bacteria and nutrient problems C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T Buttermilk Creek 5 One storm, different hydrographs C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 6 Frequency of flashiness C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 7 Storm Sewer Systems C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 8 Delivering with efficiency C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 9 Stream impact? 1974 2002 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 10 Upper Boggy Creek Incision process theory C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 11 Incision process reality Unknown Boggy at Nile C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 12 Added pollutants C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 13 Untreated delivery system ( w a t e r q u a l i t y ) C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 14 What are we doing about it? C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 15 Things to consider • O n c e i n t h e c h a n n e l w e c a n ' t d o m u c h a b o u t sto r m w ate r • We C A N m o d i f y hyd ro l o g y to m e et t h e n e e d s o f t h e st re a m b u t w e c a n ' t m o d i f y t h e st re a m to m atc h hyd ro l o g y • We C A N s h i f t t h i s p a ra d i g m w i t h b ette r re g u l at i o n , m o re i n c e nt i ve s , a n d e d u c at i o n W h at a re o u r go a l s fo r o u r st re a m s ? C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 16 Goals, thanks for asking • Fishable • Swimmable or wadable • Ecologically functional • Beautiful and lovable • More natural baseflow C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 17 Means to achieve goals • Stormwater treatment on infill development • Progressive stormwater controls (SCMs) • Green stormwater infrastructure • Changes in values and behavior (education and outreach) C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 18 So what will our legacy be? C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 19 City of Creeks Video Series https://www.youtube.com/playlist?list=PL6BHKl7gdqeyBDHZhnuY-hLQZCJcCPlX8 1. Urba n Wa ter shed F unction 2. Urba n Strea m Synd rom e 3. Stormwa ter Control Mea s ures 4. Proa ctive Prog ra m ma tic Solutions to Protect our Wa ter shed s 5. Sa la ma nd er s in the City 6. The Histor y of Austin’s Wa ter shed Protection Ord ina nces 7. Geolog ic Dra ina g e System s 8. Tra sh in Creeks Stud y C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T 20 Austin’s Major Watershed Ordinances 1. 1974 Wa terwa y Ord ina nce 2. 1980 La ke Austin/B a r ton/Willia mson Ord ina nces 3. 1983 100- Yea r Flood p la in Ord ina nce 4. 1986 Comp rehensive Wa ter s hed s Ord ina nce (CWO) 5. 1992 Sa ve Our Sp ring s (SOS) Ord ina nce 6. 2013 Wa ter shed P rotection Ord ina nce (WPO) 7. 2019 Atla s 14 Flood p la ins Ord ina nce 8. Pha s e 1 Ord ina nce req uiring Green Stormwa ter I nfra structure for most site p la ns a nd subd iv is ions H o n o r a b l e M e n t i o n : 1 9 8 2 L a n d s c a p e O r d i n a n c e ; 1 9 8 3 Tr e e O r d i n a n c e ; 1 9 9 1 U r b a n Wa t e r s h e d O r d i n a n c e ( U W O ) ; 1 9 1 1 M a x i m u m F l o o d O r d i n a n c e 21 C I T Y O F A U S T I N W A T E R S H E D P R O T E C T I O N D E P A R T M E N T