Topography in Urban Flood Model

Hi InVEST community,

This is my first time trying to use the InVEST model and I’m hoping to use the Urban Flood Risk Mitigation model to look at mitigating flood risk in portions of Wisconsin’s Driftless region. My question: Is there a way to incorporate topography into the model? The region I’m looking at is characterized by significantly steep hillsides and low-lying valleys. Rain fall on the ridges but the damage is done to the valleys. Is there a way to account for these differences and/or the flow of water?

The region is admittedly not “urban” by any standard, which may not align with the functionality of the model, but I was intrigued by the model and wanted to give it a try anyway!

I appreciate any insight you have!

Tailwinds,
Jackson

Hi @jacksonparr101, Welcome to the forums!

So, the Urban Flood Risk Mitigation model is intended to model the effect of greenspaces and soil on the damage to buildings and built infrastructure, which doesn’t sound particularly useful to an analysis in the Driftless Zone. With that said, I’d suggest taking a look at the details of the model in the User’s Guide chapter and see if the math of the model could make sense for this region.

My guess is that because of the interesting topography in the area the UFRM model probably won’t produce reasonable results.

While the UFRM model doesn’t handle topography directly, InVEST does have several other models that do route water across the landscape and model the flow of sediment (SDR), nutrients (InVEST NDR) and model seasonal water yield. None of these directly model flood risk, unfortunately.

I’m sorry I don’t have any direct solutions to this, but it sounds like an interesting problem!

@swolny, have you worked around InVEST’s lack of a flood risk model in any of the studies you’ve worked on? Or @RafaSchmitt, would you have any suggestions for modelling flood risk in this region?

James

1 Like

Hi @jacksonparr101 -

The one way that we have used existing freshwater models to give an idea of flooding is with output from the Seasonal Water Yield model. That model gives monthly and annual results for “quickflow”, which is precipitation that runs off of the landscape quickly, during a rain event, and is the flow that mainly causes flooding. We use the quickflow result (could be annual, or over the months that are part of a rainy season, etc) along with the related precipitation map(s), which are inputs to the model, to calculate an index of “flow retention”, using the simple equation

1 - (quickflow / precipitation)

(qickflow/precip) gives an idea of the ratio of precipitation that runs off, and (1-) gives the inverse ratio, the amount of precipitation that does not run off, so is being retained by the landscape. The assumption is that this retention is helping reduce flood risk downstream.

This is very simple, and only provides an index, but it is from a model that is made for mostly natural landscapes, where the Urban Flooding model is specifically designed for urban settings.

~ Stacie

1 Like

Thank you all for the thoughtful responses! It seems like maybe it isn’t the best tool for larger, rural areas. Hopefully I’ll have an opportunity to use it at some point in the future!

Jackson