12/07/2017 A continuous simulation approach Waterway Crossing Upgrades for Transport to assessing flood closures for Corridors • Upgrade crossings to achieve consistent flood major transport corridors immunity standard (e.g. 10 year ARI immunity) – May not be economical for low immunity corridor Andrew Vitale – May be better to spend money on crossings that result in longer road closures Engeny Water Management – Need to prioritise upgrades • Upgrade crossings with largest AAToC – Does not consider dependency between crossing closures – Upgrading a crossing does not necessarily reduce AAToC of entire corridor if other crossings are closed at same time • How to prioritise upgrades? Prioritisation of Waterway Crossing Upgrades Continuous Simulation Approach • Depends on many factors: • Model coincidental closures of individual – Spatial variation in rainfall along road corridor crossings along whole road corridor – Variation in immunity and AAToC of individual crossings • Can then simulate benefit of individual crossing – Closure dependency along road corridor upgrades on overall road closure characteristics – Cost of crossing upgrades – Types of road users (LV, HV) • Economic assessment can be used to prioritise – Availability and characteristics of alternative access routes or provide business case for crossing upgrades • Continuous simulation approach required to estimate AAToC for entire road corridor 1 12/07/2017 Case Study: Gore Highway Flood Study Gore Highway –––Alternative Access Routes • Gore Highway connects Toowoomba and Goondiwindi • Part of main road transport link between Brisbane and Melbourne • Road corridor 200 km long • Divided into 3 links for purpose of study based on alternative access routes • Road corridor has low flood immunity (< 2 year ARI) • Main objective of study was to develop prioritised list of waterway crossing upgrades Gore Highway –––Flooding Context Study Approach 2 12/07/2017 Continuous Hydrology –––Catchment Continuous Hydrology –––Rainfall Sequences Delineation • Minimum catchment size 2 km 2 (small • Pluviometer data used to generate gridded catchments have negligible influence on AAToC) spatial/temporal data set of 30 min interval • Not all catchments are cross drainage (flow rainfall totals parallel to road corridor can cause closures) • Gridded data used 1 km x 1 km grid size • Condamine River assessed through gauging • Continuous rainfall data set: 1973 – 2011 (39 data (no hydrology modelling required) years) • Sufficient period of record to assess closure statistics for low flood immunity road corridor Continuous Hydrology –––Rainfall Sequences Continuous Hydrology –––Flow Sequences • Continuous flow sequences developed using AWBM rainfall runoff routing model • Used catchment average rainfall data set (average of gridded data over catchment) • AWBM parameters determined by calibration against stream gauging data • Catchment area based AWBM parameters used to derive flow sequences for closure assessment 3 12/07/2017 Continuous Hydrology –––Calibration Continuous Hydraulics 280 0 280 0 260 260 • Used Flow vs Water Level rating curves at road 10 10 240 240 220 220 20 20 crossing locations from 2D flood models 200 200 180 180 30 30 160 160 • Continuous flow sequences converted to flood 140 40 140 40 Flow (m 3/s) 120 Flow120 (m 3/s) level sequences using rating curves 50 50 100 100 Catchment Rainfall (m m /hr) Catchment Rainfall (m m /hr) 80 80 60 60 • Allows assessment of coincident crossing 60 60 40 40 70 70 closures 20 20 0 80 0 80 Jan 19 Jan 23 Jan 27 Jan 31 Feb 4 Feb 8 Feb 12 Jan 2 Jan 3 Jan 4 Jan 5 Jan 6 Jan 7 Jan 8 Jan 9 Jan 10 Jan 11 Jan 12 Jan 13 Jan 14 Jan 15 Date Date Gauge Flow Model Flow Q5 Catchment Rainfall Intensity Gauge Flow Model Flow Q5 Catchment Rainfall Intensity Road Closure Simulation Tool Road Closure Statistics Annual Average Time of Closure (days) Westbrook - Pittsworth Pittsworth - Millmerran Millmerran - Murri Murri Plains Corridor 2.5 Link 0 1.3 1.8 • GoldSim model used to perform continuous Crossing - - - - - - - - 0.6 1.0 - - - - - - - - - - - - - - - - 0.1 - - 0.7 - - - 1.5 - 0.1 0.1 0.5 hydrology and hydraulic simulations • Road closure statistics calculated for each Waterway River Condamine Creek Back Creek Wyaga Creek Yarrill Creek Wyaga Creek Wyaga Tributary Creek Commorron Floodplain Creek Comorron Crossing ID 16698 50533 1651 34350 34351 25612 50601 50591 49739 24899 50688 50691 50724 50753 50757 50714 50750 50749 50747 50742 34348 34349 26242 26273 12851 22846 26331 23077 26351_P 26351_CD 26356 26350 10807 26361 26370 26373 10806 crossing, link and entire corridor: Average Duration of Closure (hr) Westbrook - Pittsworth Pittsworth - Millmerran Millmerran - Murri Murri Plains Corridor 21.5 – Average Annual Time of Closure Link 0 22.3 21.2 Crossing - - - - - - - - 37.4 17.2 - - - - - - - - - - - - - - - - 11.1 - - - - - - 18.9 - 10.2 10.8 15.6 – Average duration of closure event – Average number of closures per year Waterway River Condamine Creek Back Creek Wyaga Creek Yarrill Creek Wyaga Creek Wyaga Tributary Commorron Creek Floodplain Creek Comorron • Adopted depth > 300 mm for closure criteria Crossing ID 16698 50533 1651 34350 34351 25612 50601 50591 49739 24899 50688 50691 50724 50753 50757 50714 50750 50749 50747 50742 34348 34349 26242 26273 12851 22846 26331 23077 26351_P 26351_CD 26356 26350 10807 26361 26370 26373 10806 • Tool also gives submergence statistics (D>0mm) • AAToC for Link is smaller than sum of AAToC for individual crossings in Link – caused by coincident closures 4 12/07/2017 Crossing Upgrade Assessment Rapid Economic Appraisal • Road Closure Simulation Tool used to determine the Link AAToC that remains if a particular crossing is upgraded to mitigate closure Only minor reduction in Link AAToC Significant reduction in Link AAToC Crossing Upgrade Prioritisation Conclusions • Benefits of approach: – Fast and low cost (derivation of rating curves using hydraulic models is most time consuming component) Positive NPV – Takes into account coincident road closures along corridor – Allows rapid prioritisation of crossing upgrades Other upgrades are marginal when • Drawbacks in approach: considered in isolation – Generally limited to 30-40 years of pluviograph data – Accuracy of closure statistics may be affected for high flood immunity road corridors – Does not consider likelihood of coincident road closures along alternative routes or adjacent sections of corridor 5.