This book provides diversification-based methodologies to analyze and optimize large-scale infrastructure systems investments. It classifies and explores several metrics of diversification and integrates them with other performance objectives in a multiobjective combinatorial optimization. Additionally, the book tests the diversification metrics and the related methodologies in a case study of hundreds of millions of dollars of transportation infrastructure investments. The book shows that integrating the metrics of diversification can be useful to refine among the Pareto-optimal solutions generated using a traditional multiobjective optimization that has not considered diversification. The results suggest that the solutions that consider diversification may be more robust to emergent programmatic and technical risks, thus, identifying an opportunity to incorporate diversification-based methodologies to support a variety of problems involving infrastructure investments. The book will be of interest to decision-makers and practicing risk analysts involved in engineering, infrastructure, security, environmental protection, economics, and related topics.