Hydrotechnical Design Guidelines for Stream Crossings Alberta Infrastructure and Transportation

Design Parameters Require Y, V, Q Typical large runoff response Consistent with Physics, History Optimize crossing design Require : Y – superstructure above HW, V – design of protection works, Q – constriction, comparison Water Management – volume, timing (hydrograph) Typical : rainfall (150 – 200mm rainfall with Tp = 15 – 30hrs), snowmelt (d = 35 – 45mm, Tp = 40hrs), no frequency Water Management – more extreme for High & Large Dams Physics : channel capacity, contributing DA ; History – site, region – HWM, maintenance, rehabilitation Water Management – flood control operation Optimize : baseline boundary conditions apply to site, opening design may vary risk depending on importance - constriction, freeboard… Water Management – no net impact, spillway + aux. split

Approach 1. Channel Capacity 2. Historic Observations 3. Basin Runoff Potential Capacity – hydraulic calculation of flow that activates significant storage, implicit routing Water Management – still applicable for inflows History – HW data from files, WSC data (Q, stage), Storm database Water management – dam operation Runoff – unit discharge (runoff depth map) x contributing DA – upper bound Water management – hydrograph shaping

1. Channel Capacity Define typical channel parameters : B, T, h, S Assign stage : Calculate V, Q – AT, Manning equation Governs – most sites with overbank storage h Y < 1.0m h + 0.5m 1.0 – 2.0m 1.5 * h > 2.0m h + 1.0m Typical – field measurements, photos, survey, drawings, airphotos, satellite photos ; DTM for slope ; note man-made changes, bridge scour B – bed width, T – top of bank width, h – bank height, S – channel slope Stage – study of observed historic floods on drawings – very few > 1m over h, most BW due to bridge + flood storage activation, modification to response AT equation – 14R^0.67S^0.4, based on WSC measurements + DTM slope estimates, for B > 10m. Water Management – extension of rating curve for more extreme events

2. Historic Observations HW data from bridge files, database WSC Data – Q, Y for peak events Storm Database – ID likely response Governs – large rivers HW – HW inspection, AENV ; HWM - bridge reports, BIM, local interviews, photos, airphotos, newspaper clipping, maintenance history HW – note - headloss, debris/drift blockage, extent of flooding, scour erosion, V WSC – published Q, rating curve to Y, actual gauging. Storm – 139 historic storms, overlap basin, calc r, if > 100mm likely response.

3. Basin Runoff Potential Qp = q x A (upper bound) q - runoff depth map (cms/km2) A – contributing Storage routing Governs – small basins, steep channels Qp – upper bound for Q based on runoff potential for area q – calculate from d, Tp from runoff depth map A – exclude areas with peripheral lakes, marsh, no drainage network Routing – d/s of large lake ; rough – assumptions Water management – shape runoff hydrographs (volume, timing)

Compile Hydrotechnical Summary Concise summary Summarizes all 3 components Conclusion : Y, V, Q Consider u/s and d/s sites (HIS) Concise – 1 page Summary – brief section summarizing each of 3 techniques Conclusion – which governs, Y,V,Q to use U/s and d/s – consistent results along stream, consider more data

Tools HIS PeakFlow Storm On Basin Global Mapper Calculation – hydraulics, routing HIS – stream link, flood database, slope, file history, hydrotech summaries PeakFlow – WSC Data, query, peak Q, hydrographs, rating curves, gaugings Storm on Basin – 139 storm db, overlap calculation, graphics Global Mapper – contributing DA, S, satellite photos, DTM Hydraulics – HydroCulv, Flow Constrict, Channel Capacity Calculator