Why Risk-Informed Design Leads to Better Flood Risk Management Projects

Flood risk management projects are increasingly shaped by uncertainty. Conditions are changing, data gaps remain, and the consequences of underperforming systems are more visible than ever. Because these projects affect public safety, long-term investment, and community confidence, unexpected performance issues or late design changes can extend impacts beyond cost and schedule.

For owners, non-federal sponsors, and other stakeholders, design decisions are no longer judged solely by meeting standards, but by how well they manage risk in practice.

Traditional design criteria remain essential but are not always sufficient for understanding how a system will perform under a range of future conditions or the potential consequences of that performance. As a result, owners and sponsors are increasingly looking for ways to evaluate and reduce system risk throughout the design process. Continue reading to learn how a risk-informed approach can strengthen the delivery of flood risk management projects.

Risk-Informed Design (RID) explicitly links flood behavior, potential failure modes, and consequences to design decisions. When applied thoughtfully, it results in:

• Better-performing projects
• Reduced late-stage surprises and budgetary risk
• Support for decisions that stand up to increased technical, regulatory, and public scrutiny

What Does Risk-Informed Design Mean in Practice?

Addressing flood risk design challenges requires more than additional analysis or more conservative assumptions. It requires an approach that makes uncertainty explicit, clarifies consequences, and directly connects both to design decisions. RID does not replace established design criteria or engineering judgment, but complements them by explicitly considering uncertainty, potential failure modes, and associated consequences.

At its core, RID integrates traditional engineering analyses with an understanding of outcome likelihood and consequences. The goal is not to eliminate risk, but to understand it sufficiently to make informed, defensible decisions about how designs mitigate risk.

In practice, this means understanding how a system or component behaves in flood conditions and what the resulting outcomes mean for people, property, and communities.

For example, consider a crest raise for a segment of an existing levee. The 35% design may exceed minimum criteria for stability, seepage control, and freeboard at the modified segment. A risk-informed assessment of the design would evaluate how the raised section interacts with the full system. Modeling may show that increasing freeboard in one reach raises water levels downstream, increasing the likelihood of overtopping and flanking in adjacent areas. Potential Failure Mode Analysis (PFMA) may indicate higher seepage gradients elsewhere, increasing internal erosion risk.

RID helps designers see that improvements at one location can redistribute risk within the system, supporting targeted design adjustments that reduce overall risk rather than simply meeting standards.

Understanding Performance and Consequences of Flood Scenarios

A key component of RID is understanding how a project or system behaves under varying flood conditions and what the outcomes are. Hydrologic and hydraulic (H&H) modeling plays a key role by determining how water moves within systems, including inundation extents, flood depths and velocities, and performance during both fail and non-fail scenarios.

Breach modeling allows for evaluation of consequences across scenarios. Different failure modes may have differing consequences, and not all deficiencies result in equal risk. For flood risk infrastructure, consequences can include loss of life, direct and indirect economic costs, environmental impacts, and reputational harm. Linking modeled flood behavior to these outcomes allows designers to identify key sources of risk.

This integrated approach helps design teams compare future conditions with and without proposed actions, evaluate alternatives, and identify where risk may be transferred within a watershed. It also supports prioritizing design features that most effectively reduce risk rather than applying uniform solutions.

Risk Assessment: The Backbone of Risk-Informed Decisions

Risk assessments integrate H&H modeling outputs, consequences, and system response into a structured framework to support decision-making. Incorporating risk assessments during one or more design phases helps identify key risk drivers, evaluate how design elements impact risk, and develop recommendations to reduce risk within the authorized limits of a project.

When applied properly, risk assessment can streamline decision-making by focusing on key factors and providing a defensible basis for explaining design choices to stakeholders, regulators, and the public.

Scaling the Level of Effort to the Decision

A common concern is that RID involves extensive analysis for all projects. In practice, a key strength of RID is its scalability.

Risk assessments can range from screening-level evaluations to semi-quantitative (SQRA) and, where warranted, fully quantitative assessments (QRA). The appropriate level of effort depends on decision magnitude, potential consequences, available data, and project constraints. Applying the right level of analysis helps manage uncertainty without over-investing resources.

How Are Risk Concepts Integrated into the Design Process?

Increasingly, risk-informed approaches are integrated directly into the design process rather than applied after key decisions have been made. For example, US Army Corps of Engineers practice is moving toward structured evaluations such as PFMA during early design milestones, followed by focused risk assessments to inform final designs.

This approach allows risk considerations to shape design decisions for the greatest impact, reduce the likelihood of late-stage changes, and improve alignment between design intent and project outcomes. 

Avoiding Risk Transference and Unintended Consequences

Understanding and managing risk within a single project footprint is only part of the challenge.

Flood risk management projects do not exist in isolation. Actions taken in one location can unintentionally increase risk in other areas, such as raising flood levels downstream or affecting adjacent communities. Evaluating potential risk transference through watershed-scale modeling and pre- and post-project comparisons helps identify these effects early.

Addressing risk holistically supports better outcomes by reducing the potential for public dissatisfaction, political challenges, or legal disputes. 

For owners and sponsors, incorporating RID into planning, design, and construction leads to better-performing projects, fewer surprises, and more predictable schedules and budgets. It also provides a clearer basis for explaining decisions in environments where scrutiny is inevitable. 

Moving Toward Better, More Defensible Decisions

When applied thoughtfully and scaled appropriately, RID strengthens rather than complicates the delivery of flood risk management projects. By integrating consequences-based thinking, optimized H&H modeling, and targeted risk assessments throughout the project lifecycle, teams can better understand risk, reduce it efficiently, and deliver designs that perform over time.

If you are considering how Risk-Informed Design approaches could be applied to an upcoming project, contact me. We welcome the opportunity to talk through your objectives, constraints, and options.