Iowa Bridge Backwater Software User Manual, Version 3.0, 2016

(2016) Iowa Bridge Backwater Software User Manual, Version 3.0, 2016. Transportation, Department of

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Abstract

This manual describes how to use the Iowa Bridge Backwater software, version 3.0. It also documents the methods and equations used for the calculations. The main body describes how to use the software and the appendices cover technical aspects. The Bridge Backwater software performs 4 main tasks: - Design Discharge Entry - Stream Rating Curves - Flood-way Encroachment - Bridge Backwater - Bridge Scour Design discharge entry: You enter the design discharges you have determined via method(s) not included in the software, and describe the method you used. Stream Rating Curves: Stage versus discharge relationships for the Valley cross-section are estimated using the Manning Equation, and assuming uniform flow. Floodway: Floodway encroachments can be computed, using the methods and assumptions of the Iowa Department of Natural Resources, Water Resources Division. Bridge Backwater: The estimation of backwater from bridges is a major part of the software. The methods implemented in the software are those used by the Iowa Department of Transportation (IDOT) and Iowa Department of Natural Resources (IDNR) for Bridge Backwater Estimation. These methods are based on methodology from Hydraulic Design Series 1 (HDS-1), Hydraulics of Bridge Waterways, Federal Highway Administration (FHWA), 1970. Hydraulic Design Series 1 will be referenced throughout the manual, as HDS-1. Bridge Scour: Bridge scour (contraction, abutment and pier) is estimated from methods used by the Iowa Department of Transportation. These methods are primarily based on techniques from HEC-18, Evaluating Scour at Bridges, published by the Federal Highway Administration (2001).