Conduct Initial Flood-path Analysis

With the initial flood-path analysis step, the PDT uses the SCT to get enough of a basic understanding of the risk / flood pattern to properly develop the appropriate number of HSIPs and planning reaches. Using the study area polygon and a HSIP exported from the SCT, draw the initial study area and hazard source polylines in a GIS software tool.  The HSIP should cover all potential sources of flooding. Once these shapefiles are drawn, reimport them back into the SCT.

Select three to five AEF flood hazards and a relative sea level change (RSLC) scenario to perform flood path visualization. Run the initial floodplain analysis by toggling selected AEF flood hazards and observe flood boundary extents. Based on these results supplemented with any other relevant study considerations, the PDT should be able to decide the appropriate number and configuration of HSIPs and planning reaches needed to capture the coastal storm risk for the study.

Draw Hazard Source Interface Polyline(s) & Planning Reach Polygon(s)

Draw the number of hazard source interface polylines and planning reach polygons needed to represent/ encapsulate the risk and reimport them into the study. Ensure all HSIPs and planning reaches fall within the study area boundary (If not the study area boundary should be redrawn and reimported as well).

The shapefile template spatial organization & hierarchy rules are as follows:

• Study area boundaries should contain HSIPs and planning reaches.
• A study can have multiple study area boundaries.
• Study area boundaries can contain one or more planning reaches.
• A planning reach can contain one or more HSIPs.
• An HSIP must be linked to a single planning reach.

Once the PDT is satisfied with the study spatial arrangement via SCT shapefile templates, then study risk identification steps can begin. When drawing HSIPs and planning reaches,

Populating the Study Area Information

Populate the study area details tab of the SCT UI with information about the study. Such details include the study P2 number, study type (test or official), non-federal sponsor, the district executing the work and background information. Each entry should have a separate text box. Since a study can have multiple sponsors and multiple study authorities, each should be entered separately.

Table 1: Study Area Information

Populating the Planning Reach Polygon Data

Planning reach details for each planning reach should include a planning reach code, a planning reach name, and a location description at this stage of study development. Most of the information to be assigned to the planning reaches will occur during the risk statement development step.

Table 2: SCT Planning Reach Polygon Data

Populating Hazard Source Interface Polyline (HSIP) Data

Select each HSIP and populate the associated data within the SCT UI to begin the risk identification. Table 3 provides greater detail on the HSIP attribute fields.

Table 3: SCT Hazard Source Interface Polyline Data

Table 4. HSIP Categories

Risk Identification: Building Risk Statements

The risk identification step will culminate in a risk statement for the user-specified hazard, physical setting, exposure, and vulnerability settings. Risk statements are formulated at the planning reach level and form the basis for the planning objectives.

Hazard & Coastal System Response

Selection of H&H Parameters

Select the appropriate RSLC scenario along with three to five AEF events. This will factor RSLC into the scoping risk estimate and allow the floodplain map visualization to be generated when the risk statement is executed.

Define Hazard Sources

Select the planning reach and select ‘Build Risk Statement’ to begin. Select all hazard sources that are anticipated to drive the risk. The hazard source list shown in Table 5 includes typical hazard sources such as coastal storms, coastal erosion, tide & RSLC.  The list also includes additional sources of flooding based on the WRDA 2022 implementation guidance[1].  While there is no provision for estimating risk or risk signals for rainfall, seasonal flooding, groundwater, or other sources of flooding, these items could have a significant effect on the study scope and should be highlighted in the documentation.

Table 5: Potential Hazard Sources

A single risk statement can have multiple hazard sources.

• Selecting coastal storms enables the array of AEF events to be run as part of the risk.
• Selecting coastal erosion & wave attack enables potential wave and erosion risk signals to be part of the risk statement and included in the risk estimation.
• Selecting tide & SLC will enable the tide and SLC floodplain visualization as well as enable the tide & SLC risk signal.

Hazard Mitigators

Select all factors related to the hazard that are anticipated to mitigate the risk. These include pluvial flooding, fluvial flooding, or other. A single risk statement can have multiple hazard mitigators. Selection of these mitigators will not factor into the scoping risk estimate but will play in qualitative risk reporting and scoping task assignments and the overall study.

Coastal System Response

The physical setting components of the risk are primarily specified in section XXX.   Select the appropriate HSIP(s) from the drop down list the for the planning reach. A risk statement can link to only a single HSIP.

Physical Setting Complicators

Description of relevant physical setting items and complicating factors that would be relevant for the risk. In addition to physical setting descriptions, CSRM studies typically include relevant federal and nonfederal projects that influence the study area and may necessitate consideration when developing study analyses and assumptions.

• Existing Coastal Armor Units
• Future Coastal Armor Units Consideration.
• Hydraulically connected planning reaches
• Fringing reefs

Exposure & Vulnerability

Exposure refers to the persons and/or property subjected to harm from the hazard. Select the exposure type from the standardized list for the risk statement. Exposure types include NSI property assets, exposed populations (persons), critical infrastructure, and EJ communities. Select all exposure types that are relevant to the hazard and physical setting configuration.

Table 6: Exposure Types

First Floor Elevation Assignments

Users should provide input on the first-floor elevations prior to risk statement execution. Options for this include:

• COA-1: Use the default values in the NSI data.
• COA-2: Using a user specified average value or distribution by damage category, dynamically overwrite the FFE used as input to the damage computation. Preference for a simplified question method similar to what is used to estimate evacuation rates.
• COA-3: Use of the NSI Survey Tool – Link to the NSI Survey tool to update FFEs then perform damage computations.
• COA-4: All the above. Allow the user to choose from methods 1 - 3 for updating the FFEs.

Evacuation Rate / Estimation of Remaining Population

Simplified question method used in LSRI tool will be used to estimate the population remaining. Details to be determined.

Vulnerability

Vulnerability is the relationship between the exposure and the harm expressed as a damage driving parameter. For CSRM, damage driving parameters consist of erosion, inundation, and wave attack. Within the SCT, the damage drivers are represented as either inundation or erosion/wave attack. Select all that apply from a list of standardized damage driving parameters to build the risk statement. Selecting inundation will trigger inundation driven consequences and EAD calculations. Selecting the erosion & wave attack will allow the erosion & wave attack risk signals to be generated upon execution of the risk statement.

Execute Risk Run & Report / Visualize Risk Signals

The risk statement should be fully specified meaning all components of the risk (hazards, physical setting, exposure, vulnerability) have been entered.  The user selects ‘execute risk statement’ and the tool performs the risk estimation steps based on the options selected during the risk statement build. What is returned should be a series of risk signals aggregated by study area extent, planning reach, and hazard source interface polyline.

Risk Signals

SCT risk signals are the results generated by an executed risk statement. The signals are provided as geospatial visualizations and/or infographics to be used to inform study scoping decisions and reporting.

Floodplain Visualization Risk Signals

The floodplain risk signal displays geospatial visualizations on the depth and extent of flooding as well as the exposure impacted per selected AEF event. Exposure Items impacted include the number of NSI assets, PAR, NSI assets per EJ community, and critical infrastructure.  The user selects the AEF frequencies to be used in the floodplain visualization in section x when building the risk statement. Selecting and deselecting the floodplain in sequence between high AEF event and low AEF event should provide insight into the flood pattern. The impacted exposure displayed will be the that of the lowest frequency (most severe event).

This risk signal should help users inform decisions on potential measure performance needs given the resources at risk at key AEF events.

Table 7: Floodplain Visualization Risk Signals

NED Risk Signals

Table 8: NED Risk Signals

Life Loss Risk Signal

Table 9: Life Loss Risk Signal

EJ / Economically Disadvantaged Community Risk Signals

Table 10: E.J. Community Risk Signal

Critical Infrastructure Risk Signal

Table 11: Critical Infrastructure Risk Signal(s)

Erosion & Wave Attack Risk Signal

Table 12: Erosion & Wave Attack Risk Signal(s)

Multidimensional Flood Risk Signals

Table 13: Multidimensional Flood Risk Signal(s)

Table 14: SCT Risk Signal Summary

• NED risk signal (Estimate Consequences & EAD) – Users should be able to view consequence and risk value ranges within each planning reach
• Life Loss Signal – (T.B.D.)
• EJ Risk Signal – Users should be able to view the proportion of EAD and Life loss risk to EJ Communities within each planning reach
• Critical Infrastructure Risk Signal – A report of risk to the exposed critical infrastructure within each planning reach. (Unit of account t.b.d.)
• Erosion & Wave Attack Signals – A report on the number and exposed value of assets potentially at risk from erosion and wave attack.
• Multi-dimensional flood risk signal – This should be a report of the extent/ degree of risk sourced from multiple HSIPs (The exact structure and method of reporting t.b.d.)
• Flood Risk Visualization Analysis –.

Decision Point: Decide FWOP Scoping Risk

Based on the signal report the PDT should be able to make decisions w.r.t the risk identification.  The PDT should decide whether the risk identification step needs more work, or are the ready to move to alternative development. Considerations include the following:

• Are the risks identified appropriate given the study authority?
• Is the study spatial delineation properly organized? Are the boundary conditions appropriate? Are planning reach delineations and hazard source interface polylines reasonably representative of the risk?
• Are the risk signal quantifications appropriate and reasonable for a scoping level of effort? Are all metrics needed to characterize the risk for scoping purposes identified?
• Are all multidimensional risks identified? Are flood extent visualizations reasonable and appropriate?