1D/2D Modeling of Rivers with HEC-RAS Mapper and Applications

Although it is not possible to prevent natural disasters, it is possible to minimize the loss of life and property by reducing its destructive effects and it can be achieved with today's information and technologies. High greenhouse gas emissions due to the increasing population and the development of the industry brought with it the danger of climate change, and the management of water resources associated with this change has become even more important. Floods are disasters that cause loss of life and property by decreasing the water transmission capacity of the riverbed due to various reasons or if more water comes out of the capacity. Floods can cause significant damage to residential areas, infrastructure facilities, agricultural lands, social and economic lives of people.

The HEC-RAS (Hydrologic Engineering Centers River Analysis System) package program, developed by US Army Corps of Engineers Institute for Water Resources, Hydrologic Engineering Center, has been discussed with sample applications in my book titled OPEN CHANNEL FLOWS and HEC-RAS APPLICATIONS published in 2017. In the current 5.X versions of the program, besides one-dimensional (1D) modeling feature, two-dimensional (2D) current modeling feature has been added. The land topographic and morphological information needed in the program can be accessed using satellite data and aerial photographs. Digital Elevation Model-DEM, which is the numerical representation of topography, can now be produced with satellite data such as SRTM, ASTER, LANDSAT.

With the new features added to HEC-RAS Mapper, multi-purpose calculations can be performed in open channel flows. The program can be performing steady flow water surface profile modelling, one and two-dimensional (1D / 2D) unsteady flow modeling, semi and full unsteady flow sediment transport modelling, water quality analysis by graphic-based interface. The results can be displayed in tables and graphs, flood inundation maps can be created, animation and reporting can be done.

In this study, HEC-RAS Mapper module for the current versions of the program is explained and 2D flood modeling as well as 1D / 2D combined flood modeling applications are discussed. In the first part of the book, two-dimensional flow modeling features, advantages and constraints are explained. In the second part, the development of the land models required for 2D modeling, in the third part the development of a 1D / 2D composite model, in the fourth part, the combined model, and in the fifth part the display of the results with RAS Mapper is explained. In the sixth chapter, the subjects of when to need steady and unsteady flow modeling, where to use the 1D river breach and 2D flow area or storage areas are explained. In the seventh chapter, information is given about the Camasiri Creek and flood flows, which are discussed in sample applications.

Steady and unsteady flow analyzes were performed for flood flows in two different periods (Q25 and Q100) in the Camasiri creek. In Application 1, the Camasiri creek and its tributary Baruthane creek, are modeled as 1D for natural conditions. In Application 2, the Camasirci creek has been arranged and modeled as 1D without considering the bridges and culverts in the case of the existing canal. In Application 3, the Camasirci creek has been arranged and modeled as 1D considering the existing channel condition, bridge and culverts. In Application 4, steady and unsteady flow analyzes were carried out by placing a gate for flood protection in the current situation. In Application 5, flood analysis was achieved by performing two-dimensional (2D) unsteady flow in the Camasiri creek. In Application 6, 1D / 2D combined flow analysis was done in the Camasiri creek and flood boundaries were determined.

I wish this new book is useful for academics, planning and application engineers who work on water structures, and especially civil engineering undergraduate and graduate students who are interested in water resources. It is thought that the book may become more useful if the book is criticized and possible errors are reported.

Prof. Dr. Mehmet ARDIÇLIOĞLU

July 2020 – KAYSERİ