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3D, coupled surface-subsurface, land-atmosphere modeling

The majority of urban hydrological models focus primarily on differences in the rainfall-runoff ratio between pervious and impervious area. Impervious area (as I have mentioned in a previous post), is traditionally assumed to be the major causal source of changes in the hydrological cycle associated with urbanization. Infrastructure-centric urban hydrologic models assume that water that is infiltrated or evapotranspirated before reaching drains and pipes has “exited” the system. As more and more infiltration-based stormwater control measures are implemented however, this assumption needs to be more closely examined. Are urban soils and the urban subsurface truly effectively inexhaustible in capacity? This question is particularly important when we think about multiday rain events and changes in intensity of rainfall associated with climate change.

Too much focus on imperviousness as the cause of urban stream syndrome

For the past twenty years, the understanding that impervious surface cover as the main causal factor for the ‘flashier’ runoff response of urbanized watersheds, has been the major focus of integrated water-land planning. Such a view however, ignores other processes by which flashy runoff response may be induced through urbanization. Better understanding of specific runoff production processes and broader views of green infrastructure planning are needed.

Partial or Marginal Effects in Logistic Regression

Linear Regression In a “level-level” regression specification: $$y = beta_0 + beta_1x_1 + epsilon$$ The marginal effect of (x_1) on (y) is found by differentiating with respect to (x_1). So, (frac{dy}{dx} = beta_1) In a “log-level” regression specification: $$ log(y) = beta_0 + beta_1x_1 + epsilon $$ To get the marginal effect (frac{dy}{dx_1}), we have […]

Using SSURGO to define subsurface hydrologic conditions

I’ve known about the USGS’ SSURGO database for awhile. Back when I was practicing as a civil engineer, we mostly used it to define drainage groups of soil. I did a few land development suitability analyses for some conceptual projects with it too, but nothing too intense. For my current project, I needed to use it to define the subsurface conditions of an urban hydrological model. Here I present how to extract more detailed information from the SSURGO database.