20241106-002: Colorado River Protections Staff Report — original pdf

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10/30/24 C20-2022-0025 ORDINANCE AMENDMENT REVIEW SHEET Amendment: C20-2022-0025, Land Development Code Amendment to Title 25-7 Drainage Description: Consider an ordinance regarding amendments to Title 25 related to adequate protections to the Colorado River downstream of the Longhorn Dam. Proposed Language: To revise 25-7-32(B)(2) to establish the erosion hazard zone of the Colorado River downstream of the Longhorn Dam as 200 feet from the ordinary high-water mark, with exceptions for trails and bounded by public rights-of-way and only affecting new habitable structures and subsurface infrastructure. See Attachment A. Summary of proposed code changes: The proposed code change would expand the Erosion Hazard Zone (EHZ) associated with the Colorado River downstream of the Longhorn Dam to 200 feet from the ordinary high-water mark (federally defined river bank). The existing EHZ is measured 100 feet from the ordinary high-water mark. The EHZ would only apply to new habitable structures (e.g., residential houses) and infrastructure (e.g., new roadways, water and wastewater pipes) and NOT to existing structures and infrastructure or to new sheds, pools, patios, decks, fences, and the like. Staff are proposing that EHZ requirements for hard-surfaced trails remain at 100 feet. The EHZ would also not extend past existing public rights-of-way. Thus, for example, a property on the far side of a public roadway from river would not be subject to the EHZ. Additionally, single-family residential construction in the Extra Territorial Jurisdiction would not be affected by this ordinance since Travis County, not the City of Austin, regulates such construction. Background: This ordinance responds to Council Resolution No. 20220609-061, which initiated Land Development Code amendments related to environmental, drainage, and landscape requirements. A previous ordinance addressed many of the elements of this resolution, but certain proposed changes were not adopted at the time so that staff could conduct additional analyses and community outreach. The proposed ordinance addresses direction to staff to “evaluate the effectiveness of the 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.” Board and Commission Actions: October 16, 2024: Codes and Ordinances Joint Committee supported the staff recommendation on a vote of 6-0 with the following two amendments: 1. Recommend staff create a map for public consumption before October 28th. 2. Recommend the creation of an administrative variance to the Erosion Hazard Zone requirements at the time of building permit if there is a roadway or other structure between the development and the origin point of the buffer. 1 10/30/24 C20-2022-0025 November 6, 2024: Environmental Commission action is pending. November 12, 2024: Planning Commission action is pending. Council Action: June 9, 2022: City Council approved Resolution No. 20220609-061, initiating amendments to Title 25 related to environmental, drainage, and landscape requirements. December 12, 2024: City Council action is pending. Ordinance Number: N/A City Staff: Matt Hollon, Regulatory Policy Analyst; Liz Johnston, Interim Environmental Officer, Watershed Protection Department Phone: (512) 974-2238 Email: matt.hollon@austintexas.gov 2 10/30/24 C20-2022-0025 Attachment A: Proposed Code Language § 25-7-32 EROSION HAZARD ZONE ANALYSIS REQUIREMENT. For a preliminary plan or plat application to demonstrate that the development proposed in a preliminary plan or plat application does not create negative erosion impacts, the owner of real property may provide, at the owner's expense, an erosion hazard zone analysis. For all other development applications, the director may require the owner of real property to provide, at the owner's expense and as a condition for development application approval, an analysis to establish the erosion hazard zone if the proposed development is: (1) within 100 feet of the centerline of a waterway with a drainage area of 64 acres or greater; or (2) within 100 200 feet of the ordinary high water mark of the Colorado River downstream from Longhorn Dam, as defined by Code of Federal Regulations Title 33, Section 328.3 (Definitions) or 100 feet of the ordinary high water mark for trails and uninhabited single family residential development such as decks, patios, pools, etc.; or (3) located where significant erosion is present. (C) The erosion hazard zone analysis must be in accordance with the Drainage Criteria Manual. If an erosion hazard zone analysis is required under this section, the City may not accept for review a development application for any portion of the proposed development until the director has received the required erosion hazard zone analysis. (A) (B) (D) 3