Mustafa S. Altinakar

Short communication: A GIS-based decision support system for integrated flood management under uncertainty with two dimensional numerical simulations

A new decision support system has been developed for integrated flood management within the framework of ArcGIS based on realistic two dimensional flood simulations. This system has the ability to interact with and use classified Remote Sensing (RS) image layers and other GIS feature layers like zoning layer, survey database and census block boundaries for flood damage calculations and loss of life estimations. It also provides a user friendly interface which allows construction of user defined criteria, such as stage-damage curves, running computations and visualization of the results. Monte Carlo Simulation method is used to take into account uncertainties in various variables and parameters, and event tree analysis is used to estimate the population dynamics. The analysis of a dam break flood management strategy for Sinclair Dam in Georgia, USA is chosen as a case study to demonstrate the capabilities of the decision support system. The test results compared with HEC-FDA software indicate that this new system provides a very versatile and reliable environment for estimating various flood damage, and may greatly enhance decision making process for future design of the flood proofing facilities.

A conceptual framework of agricultural land use planning with BMP for integrated watershed management.

Land use planning is an important element of the integrated watershed management approach. It not only influences the environmental processes such as soil and stream bed erosion, sediment and nutrient concentrations in streams, quality of surface and ground waters in a watershed, but also affects social and economic development in that region. Although its importance in achieving sustainable development has long been recognized, a land use planning methodology based on a systems approach involving realistic computational modeling and meta-heuristic optimization is still lacking in the current practice of integrated watershed management. The present study proposes a new approach which attempts to combine computational modeling of upland watershed processes, fluvial processes and modern heuristic optimization techniques to address the water-land use interrelationship in its full complexity. The best land use allocation is decided by a multi-objective function that minimizes sediment yields and nutrient concentrations as well as the total operation/implementation cost, while the water quality and the production benefits from agricultural exploitation are maximized. The proposed optimization strategy considers also the preferences of land owners. The runoff model AnnAGNPS (developed by USDA), and the channel network model CCHE1D (developed by NCCHE), are linked together to simulate sediment/pollutant transport process at watershed scale based on any assigned land use combination. The greedy randomized adaptive Tabu search heuristic is used to flip the land use options for finding an optimum combination of land use allocations. The approach is demonstrated by applying it to a demonstrative case study involving USDA Goodwin Creek experimental watershed located in northern Mississippi. The results show the improvement of the tradeoff between benefits and costs for the watershed, after implementing the proposed optimal land use planning.

GIS-Based Spatial Monte Carlo Analysis for Integrated Flood Management with Two Dimensional Flood Simulation

Spatial Monte Carlo Analysis (SMCA) is a newly developed Multi-Criteria Decision Making (MCDM) technique based on Spatial Compromise Programming (SCP) and Monte Carlo Simulation (MCS) technique. In contrast to other conventional MCDM techniques, SMCA has the ability to address uneven spatial distribution of criteria values in the evaluation and ranking of alternatives under various uncertainties. Using this technique, a new flood management tool has been developed within the framework of widely used GIS software ArcGIS. This tool has a user friendly interface which allows construction of user defined criteria, running of SCP computations under uncertain impacting factors and visualization of results. This tool has also the ability to interact with and use of classified Remote Sensing (RS) image layers, and other GIS feature layers like census block boundaries for flood damage calculation and loss of life estimation. The 100-year flood management strategy for Oconee River near the City of Milledgeville, Georgia, USA is chosen as a case study to demonstrate the capabilities of the software. The test result indicates that this new SMCA tool provides a very versatile environment for spatial comparison of various flood mitigation alternatives by taking into account various uncertainties, which will greatly enhance the quality of the decision making process. This tool can also be easily modified and implemented for solving a large variety of problems related to natural resources planning and management.

Simulation of dam-break waves on movable beds using a multi-stage centered scheme

Abstract This paper presents the application of the multi-stage first-order centered scheme GMUSTA to solve a two-phase flow model with four equations for simulating dam-break floods without and with sediment transport. Computation of generalized Riemann invariants can be particularly complex and costly in simulating dam-break floods with sediment transport. GMUSTA numerical scheme, which does not require complete knowledge of the eigenstructure of the hyperbolic mathematical model, offers a suitable and attractive option. The quality of the dam-break flood simulations with GMUSTA scheme is verified by comparing the results against laboratory tests and some experimental data available in the literature, on fixed and mobile bed conditions, with different bed materials and flush or stepped bottoms. The numerical results reproduce quite well the experimental evidence, proving that the model is capable of predicting the temporal evolution of the free-surface and the bed. The GMUSTA scheme, which is not only simple to implement but also both accurate and computationally efficient, is proposed as an appropriate tool for integrating non-equilibrium sediment-transport models.

Numerical Modeling of Rainfall-Generated Overland Flow Using Nonlinear Shallow-Water Equations

AbstractThis paper presents a physics-based two-dimensional (2D) numerical model to simulate overland flows typically generated by rainfall of a storm event or multiple events in natural terrain with complex topography, landform, soil characteristics, and land use. The model is based on the 2D fully nonlinear shallow-water equations (SWEs) in which tempospatial variations of rainfall intensity and infiltration are taken into account as source and sink terms, respectively. The Green-Ampt equation is used to simulate infiltration. Due to strong nonlinearity of the coupled dynamic processes in overland flow and stormwater runoff, special efforts were made to solve this coupled-flow system under the conditions of unsteady rainfall intensity and natural terrain. To attain the modeling capabilities for multiple flow regimes including subcritical, supercritical, and the transitions, a second-order central-upwind shock-capturing scheme, which is well balanced and depth-positivity preserving, is used to solve the ...

Composite Structured Mesh Generation With Automatic Domain Decomposition In Complex Geometries

Abstract This paper presents a novel automatic domain decomposition method to generate quality composite structured meshes in complex domains with arbitrary shapes, in which quality structured mesh generation still remains a challenge. The proposed decomposition algorithm is based on the analysis of an initial Delaunay triangulation on the closed boundary of the computational domain. The virtual edges with the so-called shortest effective length of the effective concave points are identified as candidates of the interface line between neighboring blocks. As demonstrated by examples and application, the proposed algorithm is capable of effectively decomposing complex domains without holes or islands (inner boundaries) into simpler patched blocks and thus significantly alleviated the difficulties of structured mesh generation in those domains.

Simulation of Storm Surge in the Mississippi Gulf Coast Using an Integrated Coastal Processes Model

This study uses an integrated coastal processes model to simulate hydrodynamics driven by storms, tides, river inflows, and winds in a large-scale domain covering the Mississippi and Louisiana Gulf Coasts. By using existing bathymetric data and DEM topographic data, a high-resolution mesh is generated to represent structures, roads, rivers, barrier islands, and lakes. For study of flooding and inundation of hurricanes in the inland areas of the Mississippi Gulf Coast, the Pearl River and its floodplain are included in the mesh with a detailed river course. Using two synthetic storms, four hurricane scenarios are simulated by using this model. Computed maximum storm surges without the Pearl River are compared with those with the river inflow. Differences between the storm surges indicate that the inclusion of the river inflow is imperative in order to obtain accurate predictions on flood and inundation due to storm surges in the Mississippi Coast community.

Representation of Linear Terrain Features in a 2D Flood Model with Regular Cartesian Mesh

Highly transient floods resulting from the failure of dams and levees can lead to loss of life and property damage. Two-dimensional (2D) numerical simulations that use modern shock-capturing schemes are particularly suited to simulate these mixedregime floods for flood mapping, consequence analysis and emergency management planning. The Digital Elevation Models (DEM) are often used as a regular computational mesh. Unfortunately, linear terrain features, such as road and railroad embankments and dikes, which may influence flood patterns, are not adequately captured in DEMs. This study describes a two-sided cut-cell boundary method for representing linear terrain features on a regular Cartesian mesh. The proposed method is briefly described and some test simulations are presented.

Prediction of Wind, Wave, and Storm Surge due to Hurricane ISAAC in the northern Gulf Coast

This paper presents real-time predictions of wind, waves, and coastal flows by using an integrated meteorological, coastal, and ocean processes model. The highly efficient computational performance of this model enables wind and storm surge forecasting in the northern Gulf coasts including the Louisiana/Mississippi/Alabama coastal regions and the major river systems such as the Mississippi and Atchafalaya Rivers. Simulations were done on a personal computer. In the prediction of wind fields, a newly developed tropical cyclonic wind and atmospheric pressure model is used to reconstruct wind field by taking account into the hurricane decay effect after hurricane makes its landfall. The predictions for four advisory tracks of ISAAC were started before the landfall of this hurricane on Aug. 29, 2012, by using NOAAs advisory track data and the H*wind data fields. The tracks used in the study are Advisory #27, 29a, 30a, and 39. The predicted wind and storm surge are compared with the real-time observations by NOAA gauges in the area. The real-time predictions of storm surges in Isaac caught the timing of the flood peak in the Gulf coasts. The model gives more accurate water levels when the hurricane was approaching the land and the track data become more accurate. It demonstrates that this model has a good feature both in computational efficiency and accuracy to be an operational forecasting tool.

Parallelized Two-Dimensional Dam-Break Flood Analysis with Dynamic Data Structures

Numerical solution of shallow water equations using an explicit scheme are generally implemented using array type data structures. The computation is performed by sweeping the entire two-dimensional computational domain in row or column-wise order, starting with the cell in one corner and ending with the cell in the opposite corner. Although much simpler to program, this technique presents an important drawback due to the fact that it does not distinguish between wet (cells containing water) and dry cells. During a simulation, a considerable amount of computational time is spent sweeping over dry cells and skipping them once they are detected to be dry. The present study introduces a new solution algorithm which computes only those cells of the computational domain that are already wet or are becoming wet. This algorithm is especially useful for accelerating computations over very large Cartesian grids when only a small portion of cells are wet. The tracking of wet cells is achieved using dynamic data structures. This implementation takes advantage of the CFL (Courant-Friedrichs-Lewy) condition for explicit schemes, which requires that the flood propagates a fraction of the cell size during a time step. The CFL condition ensures that only the dry cells that are direct neighbors of wet cells can become wet cells. A multi-threaded parallelized version of this algorithm is implemented and tested in the CCHE2D-FLOOD TM , which is the solver of the DSS-WISE TM software developed by the National Center for Computational Hydroscience and Engineering, the University of Mississippi. The paper describes the implementation of the algorithm and discusses the performance gain achieved for different ratios of wet cells to the total number of cells.