The Regional District has, since at least 1982, regulated development within the floodplain associated with various watercourses (e.g. lakes, rivers and streams) in the Electoral Areas through its zoning bylaws.

The mapping that the Regional District has historically relied on to establish floodplains associated with Okanagan Lake, Skaha Lake, Vaseux Lake and Osoyoos Lake as well as the Okanagan River Channel were prepared by the provincial government in the 1980s and 1990s. For any land not shown on the provincial floodplain maps — such as Park Rill Creek, Horn Creek and Kearns Creek — the Zoning Bylaw has designated the following as “floodplain”;

• and that is less than 3.0 metres above the natural boundary of the Okanagan River and the Okanagan River Channel; and
• any land that is less than 1.5 metres above the natural boundary of any other watercourse.

Park Rill Creek, Horn Creek and Kearns Creek Flood Mapping Report

In 2022, the Regional District received the Park Rill Creek, Horn Creek and Kearns Creek Flood Mapping Report which was prepared by Northwest Hydraulic Consultants Limited  in response to the flooding that occurred within the Park Rill Creek, Horn Creek, and Kearns Creek watersheds during the 2018 freshet.

The main objectives of this project were to:

• Complete hydrologic and hydraulic modelling of the watersheds.
• Prepare detailed floodplain and flood hazard maps for the areas of Twin Lakes, Willowbrook, and Sportsmens Bowl Road.
• Assess the associated consequences of flooding.
• Identify mitigation measures.
• Complete a visual inspection of a 12 km reach of Park Rill Creek between near Twin Lakes and Willowbrook.

The main recommendation of the report is that “the designated floodplain maps [contained within the Report] should be adopted for flood planning purposes, including establishing flood construction levels.”, on the basis that the new floodplain maps could "limit increased flood risk from unmitigated and/or unrestricted development of the floodplain.”

The Okanagan Valley Zoning Bylaw No. 2800, 2022, currently sets out floodplain regulations which apply to Electoral Areas "A", "C", "D", "E", "F", and "I" (i.e., the Okanagan Valley electoral areas) under Section 10.0 (Floodplain Regulations) of the bylaw.

These regulations include:

• the designation of floodplain areas (via Provincial maps for the floodplain areas associated Okanagan River and Okanagan River Channel, and text for all other floodplain areas);
• the establishment of flood construction levels applicable within the designated floodplain areas;
• building/structure setbacks from watercourses;
• how flood construction level is measured; and,
• various regulations pertaining to the construction of habitable areas and other types of buildings/structures.

The floodplain areas associated with Park Rill Creek, Horn Creek and Kearns Creek do not have an associated floodplain map within Okanagan Valley Zoning Bylaw No. 2800, 2022; however, the associated floodplains are currently designated by text under Section 10.1.1(c) of the Zoning Bylaw and associated flood construction levels are established under Section 10.1.2(c) of the Zoning Bylaw (flood construction levels are measured in accordance with Section 10.3 of the bylaw). These designated floodplain areas are currently subject to development regulations under Sections 10.2 and 10.4 of the Zoning Bylaw.

Building and structure setbacks under Section 10.2 currently apply as follows:

• 7.5 metres of the natural boundary of any lake, pond or marsh, or the top of bank where the bank is within 7.5 metres of the natural boundary of any lake, pond or marsh; and
• 15.0 metres of the natural boundary of any other watercourse.

Section 10.4 of the Zoning Bylaw currently applies to these designated floodplain areas and sets out how habitable area (and other specified types of buildings) is to be constructed within a floodplain.

It is being proposed to include a new floodplain map to the Okanagan Valley Zoning Bylaw No. 2800, 2022 for floodplains associated with Park Rill Creek, Horn Creek and Kearns Creek and amend Section 10 (Floodplain Regulations) of the Zoning Bylaw based on the new mapping produced by Northwest Hydraulic Consultants.