General Notes

1. Plea se refer to the Disclaimer further b elow. OTTER LAKE 2 2. Plea se review the a ssocia ted project report b efore usin g the floodpla in m a ps: HARRIS 3 Northwest Hydra ulic Con sulta n ts Ltd. (NHC). 2020. ‘Oka n a ga n M a in stem Floodpla in M a ppin g Project’. Report prepa red for the Oka n a ga n Ba sin Wa ter Boa rd (OBWB). 2020 M a rch 31. NHC project n um b er 3004430. THOM PSON-NICOLA REGIONAL DISTRICT OF NORTH 1 2 3. This m a p delin ea tes flood con struction level (FCL) exten ts un der the design flood even t. M a ppin g of the Oka n a ga n River, REGIONAL DISTRICT Ska ha La ke, V a seux La ke, Ellison La ke, a n d La ke is b a sed on the 200-yea r m id-cen tury (2041-2070) design even t. SWAN LAKE 4 M a ppin g of Oka n a ga n La ke a n d Wood / Ka la m a lka la kes is b a sed on the flood of record (2017) a djusted to m id-cen tury for OKANAGAN 1 3 4 5 clim a te cha n ge. Trib uta ries a re n ot in cluded in m a ppin g.

4. The m a pped FCL in cludes a freeb oa rd a llowa n ce of 0.6 m a dded to the ca lcula ted flood wa ter level. It ha s b een a dded to 6 7 8 a ccoun t for loca l va ria tion s in wa ter level a n d un certa in ty in the design even t estim a tes.

5. The FCL shown on a ll la ke m a ps in clude a n a llowa n ce for win d setup (except Ellison ) a n d wa ve run up b a sed on co- 9 10 11 12 VERNON PRIEST'S occurren ce of a sea son a l 200-yea r win d even t. The win d a n d wa ve effects exten d 40 m shorewa rd to delin ea te the expected VALLEY 6 lim it of wa ve effects. Beyon d this lim it the FCL is b a sed on in un da tion of the flood even t without wa ve effects. Shoreline FCLs take precedence over lake inundation FCLs. Wave effects have been calculated based on generalized 13 14 15 16 COLDSTREAM 102 103 shoreline profile and roughness for each shoreline reach. Site specific runup analysis by a Qualified Professional may be warranted to refine the generalized wave effects should the shoreline slope be significantly different than 17 18 19 20 those summarized in the project report. The site specific analysis could increase or decrease the FCL by as much as 104 105 106 a metre.

21 22 107 108 109 6. U n derlyin g hydra ulic a n a lysis a ssum es cha n n el a n d shorelin e geom etry is sta tion a ry. Erosion , deposition , degra da tion , a n d a ggra da tion a re expected to occur a n d m a y a lter a ctua l ob served flood levels a n d exten ts. Ob struction s, such a s log-ja m s, loca l storm wa ter in flows or b locka ges or other la n d dra in a ge, groun dwa ter, or trib uta ry flows m a y ca use flood levels to 23 24 110 111 exceed those in dica ted on the m a ps.

7. The Oka n a ga n floodpla in is sub ject to persisten t pon din g due to poor dra in a ge. Persisten t pon din g is n ot covered b y the flood 25 26 112 113 in un da tion m a ppin g.

27 28 8. The m a jority of the Oka n a ga n River is diked; b rea chin g of the dike wa s n ot m odelled. Isola ted a rea s b elow the FCL (a s 114 projected perpen dicula r to flow from the cha n n el), such a s those la n dwa rd of the dikes, a re m a pped a s in un da ted. This delin ea tion a ccoun ts for poten tia l fa ilure a n d b rea chin g of the dike, seepa ge through, or in flows tra pped b ehin d the sepa ra tin g REGIONAL DISTRICT OF LAKE 29 30 CENTRAL dike or em b a n km en t. This a pproa ch is con sisten t with British Colum b ia floodpla in m a ppin g guidelin es. DUCK LAKE 7 9. Filterin g wa s used to rem ove isola ted a rea s sm a ller tha n 100 m 2. Holes in the in un da tion exten t with a rea s less tha n 100 m 2 31 32 115 were a lso rem oved. Isola ted a rea s la rger tha n 100 m 2 were reta in ed for m a ppin g if they were within 40 m etres of direct in un da tion or within 40 m etres of other reta in ed polygon s. 33 34 116 10. Oka n a ga n Da m b rea ch a n d da m overtoppin g were n ot m odelled. On the right b a n k of the Oka n a ga n River from the Oka n a ga n Da m down strea m to the Highwa y 97 b ridge, in un da tion m a ppin g is b a sed on m odellin g of design la ke level 35 36 overflowin g to the river down strea m ; a lon g the left b a n k down strea m of Oka n a ga n Da m in un da tion m a ppin g is b a sed on river m odellin g, a s Oka n a ga n La ke level overtoppin g a lon g the left b a n k is lim ited to a loca lized a rea a dja cen t to the da m . Overflow a t this site wa s n ot sim ula ted. 37 38

TSINSTIKEPTUM 10 11. The a ccura cy of sim ula ted flood levels is lim ited b y the relia b ility a n d exten t of wa ter level, flow, a n d clim a te da ta . The a ccura cy of the floodpla in exten ts is lim ited b y the a ccura cy of the design flood flow, the hydra ulic m odel, a n d the digita l 39 40 WEST surfa ce represen ta tion of loca l topogra phy, which is b a re-ea rth (n o b uildin gs or structures). Loca lized a rea s a b ove or b elow KELOWNA the FCL m a y b e gen era lized b y the in un da tion m a ppin g. Therefore, floodpla in m a ps should b e con sidered a n a dm in istra tive tool tha t in dica tes flood eleva tion s a n d floodpla in b oun da ries for a design a ted flood. A Qua lified Profession a l is to b e TSINSTIKEPTUM 9 41 42 43 MISSION CREEK 8 con sulted for site-specific en gin eerin g a n a lysis.

44 45 46 47 48 12. In dustry b est pra ctices were followed to gen era te the floodpla in m a ps. However, a ctua l flood levels a n d exten ts m a y va ry from those shown . Residua l flood risk b eyon d tha t m a pped exists for flood even ts m ore extrem e tha n the design even ts. OBWB a n d NHC do n ot a ssum e a n y lia b ility for va ria tion s of flood levels a n d exten ts from tha t shown . 49 50 51 52 53 54 55

56 57 58 Data Sources

1. Design flood even ts a re b a sed on hydrologic m odellin g of the Oka n a ga n River wa tershed. The hydra ulic respon se is b a sed 59 60 on a com b in a tion of 1D a n d 2D n um erica l m odels developed b y NHC usin g HEC-RAS softwa re, a n d NHC SWAN m odels. The hydra ulic m odels a re ca lib ra ted to the 2017 flood even t a n d va lida ted to the 2018 flood even t; due to lim its on da ta 61 62 63 a va ila b ility the hydrologic m odel is ca lib ra ted usin g da ta from 1980-2010.

2. The digita l eleva tion m odel (DEM ) used to develop the m odel a n d m a ppin g is b a sed on Lida r da ta collected from M a rch to 64 65 66 Novem b er 2018 a n d provided b y Em ergen cy M a n a gem en t BC (EM BC), cha n n el survey con ducted b y WSP in M a rch, April, a n d Jun e 2019, a n d a ddition a l survey da ta . See a ccom pa n yin g report for deta ils NHC (2020).

67 68 3. Orthophoto im a gery provided b y EM BC a n d a cquired in 2018. Addition a l b a se m a ppin g a n d orthoim a gery from Esri.

SUMMERLAND 4. Na tion a l Ra ilwa y Network ra ilwa y lin es a cquired from Na tura l Resources Ca n a da . 69 70 5. Dike crest lin es pub lished b y the M in istry of Forests, La n ds, Na tura l Resource Opera tion s a n d Rura l Developm en t – Wa ter 71 72 M a n a gem en t in 2019 a n d a cquired from Da ta BC.

REGIONAL DISTRICT OF 6. Adm in istra tive b oun da ries a cquired from Da ta BC. 73 74 KOOTENAY BOU NDARY

PENTICTON 75 76 Disclaimer

PENTICTON 1 77 PENTICTON 2 This docum en t ha s b een prepa red b y Northwest Hydraulic Consultants Ltd. for the b en efit of Okanagan Basin Water Board, Regional District of North Okanagan, Regional District of Central Okanagan, Regional District of Okanagan- REGIONAL DISTRICT OF Similkameen, Okanagan Nation Alliance for specific a pplica tion to the Okanagan Mainstem Floodplain Mapping Project, OKANAGAN-SIM ILKAM EEN 78 79 Okanagan Valley, , Canada (Ellison, Wood, Kalamalka, Okanagan, Skaha, Vaseux, and Osoyoos lakes and Okanagan River from to Osoyoos Lake). The in form a tion a n d da ta con ta in ed herein represen t Northwest Hydraulic Consultants Ltd. b est profession a l judgm en t in light of the kn owledge a n d in form a tion a va ila b le to 80 81 Northwest Hydraulic Consultants Ltd. a t the tim e of prepa ra tion , a n d wa s prepa red in a ccorda n ce with gen era lly a ccepted en gin eerin g pra ctices.

82 Except a s required b y la w, this docum en t a n d the in form a tion a n d da ta con ta in ed herein a re to b e trea ted a s con fiden tia l a n d m a y b e used a n d relied upon on ly b y Okanagan Basin Water Board, Regional District of North Okanagan, Regional 83 District of Central Okanagan, Regional District of Okanagan-Similkameen, Okanagan Nation Alliance, its officers a n d em ployees. Northwest Hydraulic Consultants Ltd. den ies a n y lia b ility wha tsoever to other pa rties who m a y ob ta in a ccess to this docum en t for a n y in jury, loss or da m a ge suffered b y such pa rties a risin g from their use of, or relia n ce upon , this report 84 85 or a n y of its con ten ts.

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OLIVER 89

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OSOYOOS 1 92

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OSOYOOS 3 95 96 97

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1:5,000 SCALE M AP SHEET d x m ± . 5

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North V a n couver, B.C. V 7M 3G3 v i t c A Ca n a da Engineer GIS Reviewer \ s t c

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VCCB MSN/MAO/SWM o r

Fa x: 604.980.9264 P \ n a www.n hcweb .com v -

Job Number Date e l i f n i 3004430 30-APR-2020 a m \ \