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Pages 48-65

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From page 48...
... 48 This chapter compiles the information that was obtained through interviews with personnel from three state DOTs that are involved in designs or studies that used hydrologic modeling, supporting the synthesis objective of documenting state DOT use of DRRMs. In particular, these agencies were selected from the list of 16 state DOTs that have reported using DRRMs in their hydrological practices.
From page 49...
... Case Examples 49 Figure 32. Paths of Hurricanes Matthew (left)
From page 50...
... 50 Resilient Design with Distributed Rainfall-Runoff Modeling derive effective rainfall hyetographs that could be used in the HEC-RAS 2D. Each of the four sub-watersheds presented in Figure 33 was supplied with a single hyetograph in HMS, and these were readjusted for input in HEC-RAS 2D.
From page 51...
... Case Examples 51 more conservative CN values from Hurricane Matthew calibration were used for the Design Event using the 100-year hyetograph. • Hydraulic modeling: HEC-RAS 2D models were supplied with adjusted hyetographs that resulted from HEC-HMS.
From page 52...
... 52 Resilient Design with Distributed Rainfall-Runoff Modeling Figure 35. HEC-RAS 2D grid at Lumberton, NC (AECOM 2020)
From page 53...
... Case Examples 53 In general, the agreement between the model and observed water levels is very good, with discrepancies less than 0.4 feet. A similar map was derived for Hurricane Florence, also with good results and discrepancies between modeled and observed high water marks less than 0.7 feet (AECOM 2020)
From page 54...
... 54 Resilient Design with Distributed Rainfall-Runoff Modeling Figure 37. Overtopping and flooding of KY 11/15 (East College Avenue)
From page 55...
... Case Examples 55 by entrance pipes. For the development of the hydrological study, two watersheds, Study Area 1 and Study Area 2, were created to represent the west and east sections of the flooded roadway within the project corridor.
From page 56...
... 56 Resilient Design with Distributed Rainfall-Runoff Modeling In order to assess the effectiveness of the PCSWMM, a total of 10 points of interest were identified -- five in each of the two study areas -- which included lots that experienced flooding. Modeling results for Study Areas 1 and 2 are shown in Figures 40 and 41, respectively.
From page 57...
... Case Examples 57 The same modeling framework used to diagnose the issues of flooding was used to assess the impacts of various strategies to avoid these issues. The alternatives that were modeled in PCSWMM included increasing culvert conveyance, improving ditch grading, reducing Manning roughness of ditches, and using detention basins to retain flows and control discharges.
From page 58...
... 58 Resilient Design with Distributed Rainfall-Runoff Modeling has been using hydrological models such as HEC-HMS and GSSHA for bridge scour estimates, providing peak flow estimates that can be used in hydraulic estimates of bridge scour. This section presents one case example in which DRRM results were used and compared with predictions from lumped and semi-distributed approaches.
From page 59...
... Case Examples 59 Figure 44. GSSHA grid of Big Sulphur Creek watershed overlaid on soil type data and land use (Vigneswaran 2022)
From page 60...
... 60 Resilient Design with Distributed Rainfall-Runoff Modeling in the model was computed using the Green-Ampt approach, and the channel routing used the diffusion wave (i.e., zero-inertia wave equation) approach.
From page 61...
... Case Examples 61 Figure 47. Results of GSSHA modeling for the two 100-year peak flows based on the SCS Type IA rainfall distribution (Vigneswaran 2022)
From page 62...
... 62 Resilient Design with Distributed Rainfall-Runoff Modeling TxDOT has adopted DRRMs in the past for different roadway projects that evaluate the potential impacts of large inflows to roadways. This synthesis presents the status of an ongoing project associated with the resiliency of the I-10 corridor (92 miles)
From page 63...
... Case Examples 63 (A)
From page 64...
... 64 Resilient Design with Distributed Rainfall-Runoff Modeling The other approach to obtain distributed rainfall was based on gridded radar rainfall data complemented with ground rain gages. Two sources were used: the 4 km × 4 km gridded radar rainfall data from National Centers for Environmental Prediction/Environmental Modeling Center (NCEP/EMC)
From page 65...
... Case Examples 65 observed but also simulated scenarios in which the conveyance was improved and attenuated the reported flooding. • The case example of Caltrans presented a case in which GSSHA was used to provide precise hydrological estimates of peak flows that were used in turn for scour calculations in bridges.

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