Historical events
FloodAdapt gives users the option to select and modify historical events, which they can then build what-if scenarios around. This is a powerful feature that engages stakeholders and facilitates a concrete understanding of risks and effectiveness of measures. For example, if a community experienced a high tide flood event, they can explore how that same event will look in the future as sea level rises, or how it would have been worsened had it coincided with rainfall. They can test out different measures and assess how effective they would be against this type of event. Historical events also allow users to develop confidence in the system (or identify model-improvement needs) by comparing with their experience or measurements of where floods and impacts occurred in the event.
Below is a video that demonstrates the creation of a historical event, followed by complete documentation on all the options for creating and modifying historical events.
When a user selects the “Historical” option from the Events tab, they will see the event template window shown in Figure 1. This window allows the user to input (historical) time series for:
The event window also allows users to modify these elements with synthetic options to create what-if event scenarios around a historic event. For example, a user could add synthetic rainfall to a historical king tide event.
Users can view the time series for the different event components in the ‘plotting’ section of the event template window (see Figure 1). The dropdown menu “Forcing” allows users to select any of the four components. Users can select the component they want to view, and then click “Generate plot” to visualize the time series.
Water levels
The water level time series for the historical event can be specified in different ways (see Figure 1). These are:
Gauged - if a gauge exists at the site and has been connected to the system at setup, the option “gauge” will be selected by default, and water levels for the selected time period will be automatically downloaded and displayed. If the user changes the start or stop time, they will need to click ‘download water levels’ to refresh the download and the display.
CSV - users can import water level time series as a two-column CSV file. The first column should contain the date and time in the format yyyy-mm-dd hh:mm:ss, and the second column the water level relative to the reference level for the site (for example, mean lower low water). There is an “i” button next to the option to import a time series. Clicking this button will display an example of the format required for the CSV, including the water level units and reference.
Synthetic - when users have a historical record of rainfall or river discharge, but water levels were unknown or unmeasured, users can choose to generate a synthetic water level time series. The simple option is to specify a peak water level (default is average high tide), and the duration of the peak. Advanced options are described in the synthetic event documentation.
In this documentation, we refer to water levels as the combined effect of (1) astronomoical tide and (2) the surge caused by wind.
Rainfall
The user has the following options for specifying a rainfall time series for the event:
None - Selecting this option means that no rainfall will be included in the calculation.
Constant - For a constant rainfall, the user is asked to enter a rainfall intensity. This rainfall will be applied over the entire duration of the event.
CSV - The user can upload a two-column CSV file with the rainfall time series. The first column contains the date and time in the format yyyy-mm-dd hh:mm:ss, and the second column contains the rainfall intensity (depth/time). The units of the rainfall will depend on how the system is configured. In the event specification window, when you choose ‘CSV’ for the rainfall source, you will see an “i” button appear. Clicking this button will display an example of the format required for the csv, including the rainfall intensity units. There is an option to increase the rainfall by a fixed amount (“precipitation multiplier”). All rainfall values in the time series will be multiplied by the value entered in this field.
Synthetic - The synthetic option allows users to build what-if rainfall scenarios to explore what would have happened if they had coincided with historical water level events, like a high tide event. The synthetic options ask a user for the cumulative rainfall, the duration of the rainfall, and a time when the peak rainfall occurred. More details about the synethtic options are covered in the synthetic event documentation.
Wind
The user has the following options for entering time series for the wind:
None - Selecting none means no wind will be included in the calculation.
Constant - For a constant wind speed, the user is asked to enter the wind speed and wind direction.
CSV - The user can upload a wind time series; this should be a three-column csv. The first column contains the date and time in the format yyyy-mm-dd hh:mm:ss, the second column contains the wind speed, and the third column contains the wind direction. The units of the wind speed and direction will depend on how the system is configured. In the event specification window, when you choose ‘CSV’ for the wind source, you will see an “i” button appear. Clicking this button will display an example of the format required for the csv, including the units.
The largest effect of wind on flooding is the surge it causes in the nearshore water levels. For gauged or synthetic nearshore water levels, this effect is already included. The (more limited) role wind plays in this event type is to skew the water levels from the model boundary (usually near the gauge) to the land. Unless this is of particular interest to a user, the wind can be ignored.
River discharge
The river discharge represents the discharge in a river at the model boundary. If there are multiple rivers at the model boundary, the user will be able to select each river to specify the discharge. The user has three options for specifying the river discharge time series: a constant discharge, an uploaded time series, or a synthetic time series.
Constant - by default, this option is selected and an average discharge value is used; this value is specified in a FloodAdapt configuration folder at system setup. The user can change the value of the constant discharge in the event specification window.
CSV - The user can upload a river discharge time series; this should be a two-column csv. The first column contains the date and time in the format yyyy-mm-dd hh:mm:ss, the second column contains the river discharge. The units of the river discharge will depend on how the system is configured. In the event specification window, when you choose ‘timeseries’ for the river discharge source, you will see an “i” button appear. Clicking this button will display an example of the format required for the csv, including the units.
Synthetic - The synthetic option allows users to build a synthetic river discharge time series. The synthetic options ask a user for peak discharge above base discharge, the duration of the discharge wave, and the time when the peak discharge occurs (relative to the start of the selected time period). The base discharge is automatically set to the average discharge, but can be modified. More details about the synthetic options are covered in the synthetic event documentation.