Core+ NatureInsight – Applying Hydrology in Watersheds

Once NbS opportunities have been mapped across a catchment area, an important functionality within NatureInsight is the ability to assess the impact of the NbS on flows within the catchment. NatureInsight can generate hydrographs and assess the impact of storage volumes associated with the NbS interventions. The functionality of assessing the impact of storage volumes is based on Scalgo's unique tool for generating hydrographs and adapted to suit the Arup developed Aggregate Storage Model (ASM). The ASM is a hydrological routing model, that can be used to assess the impact of semi-distributed water storage across sub-catchments. NatureInsight allows the user to allocate a total (or aggregate) storage volume to each of the sub-catchments to assess the impact of storage on the selected sub-catchment. It can also assess the peak flow impact of the combined effect of different sub-catchments at a downstream point of interest.

Generating a Hydrograph

A hydrograph for a catchment can be generated by clicking the green hydrograph within the right sidebar. This opens the hydrograph window.

By default, there are six rain events generated for a catchment area, the 10-year, 20-year, 50-year, 100-year, 200-year, and 500-year. Clicking between the different rain events changes the hydrograph as desired. The default rain events within NatureInsight cannot be altered, however, custom rain events can also be added for a catchment area by clicking the + button. New events can be generated in four ways, from a blank starting point, from the existing rain events within the tool, added from an outside project, or imported from a file. The option to create an event from the existing rain events allows you to alter the depth and duration of the event.

The velocity and baseflow can be altered for the catchment, and suggested values are provided for both, by clicking ‘Set to NatureInsight’ and ‘Save’. The suggested values have been calculated using documented hydrological approaches discussed in the NatureInsight Whitepaper. Similarly, the ‘NatureInsight’ option is used to match infiltration parameters with spatial data from derived Hydrology Of Soil Types (HOST) from the watershed. More information is provided on this in the NatureInsight Whitepaper. 

Applying Storage Volumes from NbS

For a selected hydrograph the storage volumes can be applied from the NbS Opportunity Mapping that is currently shown. To apply these to the hydrograph click the ‘Edit Interventions’ button, which opens a second window. In this window click the button ‘Add from NatureInsight’. This applies the storage across three bucket types – Land Use, Runoff, and Floodplain. Each bucket represents a range of NbS interventions to capture the different behaviour in terms of interacting with flow. For more information on the types of intervention and how they have been allocated to the three buckets, check the NatureInsight Whitepaper.

For each bucket type different parameters can be altered to edit the assumed design of the NbS, for example altering the diameters of feature outlet pipes, or changing the threshold at which flow would enter an intervention. To see the impact of interventions you must also click the ‘NatureInsight’ button under ‘Intervention Scenario’ in the original window. The impact of the changes can be seen on the hydrograph in the original window, which visualises the impact of each bucket. The reason for having this extra button here is so you can quickly flick between scenarios with and without storage. More information on the parameters is provided in the NatureInsight Whitepaper. When the interventions parameters are edited – NatureInsight enables you to test the parameter design for the design storm event you are using against all the other available storm magnitudes. This enables you to, say, design your NbS for a 50-year event, and then test that design against the 10-year, 20-year, 100-year and so on.