14 C20-2022-025 - Colorado River Protection Staff Presentation — original pdf

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Overview of the Colorado River Protections Ordinance P l a n n i n g C o m m i s s i o n D e c e m b e r 1 0 , 2 0 2 4 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 Introduction One simple change to the Land Development Code: Change the Erosion Hazard Zone from 100 to 200 feet, downstream of Longhorn Dam Plus introduce: Improve drainage design rules to reduce extreme bank erosion 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 2-Minute Summary Video 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 Ordinance Youtube video link Council Resolution Community members asked Council to strengthen Colorado River protections; Council thereafter included in their June 2022 Council resolution: “… evaluate the effectiveness of existing Critical Water Quality Zone and Erosion Hazard Zone buffers on the Colorado River downstream of the Longhorn Dam and to propose protections that will provide adequate protections to the river that will ensure a healthy riparian corridor to stabilize the riverbank and protect property from erosion” 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 East Austin Longhorn Dam J. Trevino Metro Park Lady Bird Lake Roy Guerrero Park “Dog’s Head” Southeast Austin Parcel Count Juris- diction Type Acres CWQZ Buffer Acres 400ft Buffer Acres Austin’s Full Purpose (City) Limits 1,054 14,896 15,950 391 2,184 2,575 281 1,929 2,211 241 243 484 50% 50% 100% 7% 93% 100% 13% 87% 100% 15% 85% 100% Acres 400ft minus CWQZ 109 255 ABIA 364 30% 70% 100% FULL ETJ Totals FULL ETJ Totals Hornsby Bend Biosolids Plant Tesla SHEC/SAR WWTP Austin’s ETJ Travis County Austin’s Colony Colorado River City Limits & ETJ 5 Single-Family Residential Parks & Open Space Industrial Parks & Open Space Agriculture / Undeveloped Parks & Open Space Mining Single-Family Residential Utilities Single-family home construction in ETJ not affected 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 Colorado River Land Uses 6 Current Protections along River/Creeks 1. 100-Year Floodplain 2. Critical Water Quality Zone (CWQZ) buffer 3. Erosion Hazard Zone review buffer L a d y B i r d L a k e • Each zone covers a different purpose, area, and restrictions • Restrictions may differ in COA, ETJ* and Travis County • Both the current and proposed Erosion Hazard Zone are entirely overlapped by the Critical Water Quality Zone • The erosion hazard zone works closely with the Critical Water Quality Zone and can fill in some gaps in regulation 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 * COA = City of Austin; ETJ = Extraterritorial jurisdiction P u r p l e a r e a s s h o w 1 0 0 - y e a r f l o o d p l a i n s 7 Current Protections along River/Creeks 1. 100-Year Floodplain 2. Critical Water Quality Zone (CWQZ) buffer 3. Erosion Hazard Zone review buffer 100-Year Floodplain Width varies L a d y B i r d L a k e 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 P u r p l e a r e a s s h o w 1 0 0 - y e a r f l o o d p l a i n s 8 Current Protections along River/Creeks 1. 100-Year Floodplain 2. Critical Water Quality Zone (CWQZ) buffer 3. Erosion Hazard Zone review buffer Critical Water Quality Zone 200 to 400 ft wide L a d y B i r d L a k e 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 P u r p l e a r e a s s h o w 1 0 0 - y e a r f l o o d p l a i n s 9 Current Protections along River/Creeks 1. 100-Year Floodplain 2. Critical Water Quality Zone (CWQZ) buffer 3. Erosion Hazard Zone review buffer Critical Water Quality Zone Fixed 400 ft wide L a d y B i r d L a k e *** 400ft Fixed CWQZ NOT RECOMMENDED *** Existing buffers provide good protection, best fit the terrain, no additional impacts 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 P u r p l e a r e a s s h o w 1 0 0 - y e a r f l o o d p l a i n s 11 Current Protections along River/Creeks 1. 100-Year Floodplain 2. Critical Water Quality Zone (CWQZ) buffer 3. Erosion Hazard Zone review buffer Erosion Hazard Zone Existing 100 feet wide L a d y B i r d L a k e 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 P u r p l e a r e a s s h o w 1 0 0 - y e a r f l o o d p l a i n s 12 Current Protections along River/Creeks 1. 100-Year Floodplain 2. Critical Water Quality Zone (CWQZ) buffer 3. Erosion Hazard Zone review buffer Erosion Hazard Zone Proposed 200 feet wide L a d y B i r d L a k e *** 200ft EHZ RECOMMENDED *** Much better fit the height of banks and scale of river energy 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 P u r p l e a r e a s s h o w 1 0 0 - y e a r f l o o d p l a i n s 13 Why are we proposing this? S A N D !  Public safety  Highly erosive area  Public expenditures to stabilize erosion sites  Prevent public and private losses due to erosion  Tens of millions of dollars in damage and counting…  The current erosion hazard zone geometry does not fit the large scale of the river 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 House on river in ETJ Knollwood on the Colorado Tillery St. Storm Drain Hergotz Ln. Roy Guerrero Park / Krieg Fields Colorado River: Erosion Case Studies Austin’s Colony 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 Falwell Lane 3 2 0 2 , 5 . n a J m o r f e g a m i p a M r a e N 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 ~90 feet Stranded tree, formerly on edge of bank Knollwood on the Colorado Fallwell Lane: 2015 Halloween Flood Access to two critical facilities cut off—for the 2nd time 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 Home threatened after 20ft bank failure, May 2015 Hergotz Lane 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 Ordinance Proposal • Increase EHZ review buffer from 100ft to 200ft width • Only applies to new “habitable space” and infrastructure  Change affects EHZs citywide (not just along river) • No change for hard-surfaced trails (100ft EHZ remains the same) • Does not extend beyond parallel public roads • Add an administrative variance for greater cut and fill to support the provision of EHZ protective works 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 * EHZ = Erosion Hazard Zone 19 Ordinance Proposal • Affects foundation design and cost for single-family building permit projects  Not applied to existing structures or new driveways, decks, etc.  Not applied to new single-family construction in the ETJ*  Single-family building permits regulated by County only, not City of Austin • NO or VERY LOW IMPACT on new subdivision or commercial projects (site plans)  The proposed 200ft EHZ is entirely within the existing Critical Water Quality Zone (CWQZ)  Possible impact on stormwater infrastructure in CWQZ  Subdivisions in ETJ also unaffected (EHZ remains 100ft) • Potential impact on redeveloping commercial projects 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 * ETJ = Extraterritorial jurisdiction Level 1 EHZ Diagram: Existing 100ft EHZ Review Buffer Protective works or Engineer Level II required Protective works not required Outside EHZ 100ft EHZ Review Buffer Water surface Starting point = lowest surface contour line Outside of critical slope 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 21 Level 1 EHZ Diagram: Proposed 200ft EHZ Review Buffer Protective works or Engineer Level II required Protective works not required Outside EHZ 200ft EHZ Review Buffer Water surface Starting point = lowest surface contour line Can use topo contour in Property Profile web tool Outside of critical slope 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 22 Level 1 EHZ Diagram: Proposed 200ft EHZ Review Buffer Protective works or Engineer Level II required Protective works not required Outside EHZ 200ft EHZ Review Buffer Water surface 20ft Place subsurface utilities min. 20ft below channel bottom (if less must demonstrate via Level 2 analysis) 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 23 Schedule Since 2023 Sep./Oct. Oct. 28 Oct./Nov./Dec. Oct. 16 Nov. 6 Dec. 10 Jan. 30 Jan. to Mar. Develop staff recommended ordinance Gather stakeholder input on ordinance In-Person WPD outreach meeting (Montopolis Rec. Center) Present ordinance to Commissions and Council Codes & Ordinances Joint Committee Environmental Commission Planning Commission City Council Develop/solicit stakeholder feedback on Criteria Changes Interactive map of Erosion Ordinance 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 24 Discussion 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 25