This software is used for calculating peak flow at given points (typically, inlets/catch basins) over a hydrologically-corrected DEM.

This software encompasses work originally developed by the Cornell Soil & Water Lab (on GitHub @ github.com/SoilWaterLab). see Credits/Contributors, below.

This repository represents a hard fork of the Water Lab's Culvert_Beta repository. Code from the original repository is limited primarily to equations found in /core/logic/calc.py.

In summary, this toolset will determine the runoff peak discharge of given point's watershed using the SCS graphical curve number method. For more information on this method, see Technical Release 55.

This toolbox relies on:

• the ArcPy package in ArcGIS Pro
• PETL, a package for easily building data extract/transform/load workflows
• Pint, a package for working with units
• Click, a package that helps provide a CLI for these tools
• pytest, for testing

As ArcGIS Pro is Windows-only software, this works only on Windows (see Plans, near the end of this Read Me)

There are a few ways to install. If you're unfamilar with Python Conda environments and plan on using this stricly within ArcGIS Pro, then start here:

Download (or clone) the contents of this repository to your computer.

First, start with these instructions for creating and activating an environment on Esri's help site.

Then, move on to the instructions for installing available packages.

Following those instructions, you'll need to install four packages:

• PETL
• Pint
• Click
• pytest

Once those are installed, make sure your new environment is active. You will likely need to restart ArcGIS Pro.

(skip this if you installed per the instructions in the previous section)

• create a new Conda environment from the command line
• install packages from the included requirements.txt file to the environment.
• activate the environment in ArcGIS Pro

In your ArcGIS Pro project connect to a toolbox (follow these instructions if you haven't done it before).

The Peak Flow calculator takes several inputs:

• input point locations, representing locations at which peak flow is to be estimated
• a raster indicating flow direction
• a raster indicating slope (in percent)
• a raster indicating curve numbers calculated according the the TR-55 method. At this time the curve number raster must use a CRS with meters for units.
• a preciptation frequency estimates table from NOAA (/sample_data/noaa_precip_table.csv for the duration and frequencies expected by this tool)

From these, it calculates peak flow for every input point. Peak flow results are reported in cubic feet/second for every storm frequency from 1 to 1000 year storm.

An ArcToolbox is provided for running these scripts in ArcGIS Pro, PeakFlow.tbx.

Two scripts are used to build and/or prep a curve number raster, which is a prerequisite for running the tool.

• Build Curve Number Raster: build a Curve Number Raster from scratch, using landcover, soils, and curve number lookup CSV file. A sample of the lookup table, which maps landcover class values to soil values and TR55 curve numbers, is available in /sample_data/urbantreecanopy_curvenumber_lookup.csv.
• Prep Curve Number Raster: if you already have a curve number raster from another source, this tool will snap and reproject it to a reference raster, which should be the DEM raster for the study area.

Three scripts run the Peak Flow Calculator:

• Peak Flow Calculator: the basic implementation of the peak flow calculator logic
• Peak Flow Calculator - Interactive: allows for pour points to be added interactively on the map, instead of from an existing layer
• Peak Flow Calculator using Pre-Calc'd Basins: same as the basic implementation, but allows the user to additionally provide a watershed basin raster as input

You can run the toolbox outside of ArcGIS Pro from the command line, as long as ArcGIS Pro is installed/licensed on your machine.

Currently, the CLI exposes a few, slightly different versions of the tools described above:

• Peak-Flow Calculator "Lite". Same as the basic implementation available in ArcToolbox tool above.
• Peak-Flow Calculator "Full": an implementation of the peak flow calculator logic that automatically calculates flow direction and slope inputs from a DEM at run-time.
• Prep Curve Number Raster: Same as the ArcToolbox tool above.

Available commands will likely coorespond with available ArcToolbox tools in future iterations of this codebase.

• scripts in the core/ root provide interfaces between the business logic contained in core/logic/ and the ArcToolbox; Those suffixed by _tbx are referenced directly by tools in PeakFlow.tbx
• core/logic/ contains the business logic. The logic module itself contains one function, main, which handles orchestrating the various underlying components end-to-end.
• core/logic/calc.py contains the equations used to calculate peak flow.
• core/logic/data_io.py is used for reading in preciption tables (and is where to park other custom data ingest routines)
• core/logic/gp.py contains all functions that perform geoprocessing using the ArcPy package, including reading and writing spatial datasets
• core/logic/utils.py contains utilty functions.

See the wiki for more information on the business logic.

• We plan to develop a platform-agnostic version of this toolset that is not dependent on Esri licensing in the future.

• These scripts are based on the culvert evaluation model developed by Rebecca Marjerison at the Cornell Soil and Water Lab in 2013
• David Gold, python script development, August 4, 2015
• Object-oriented structure and resiliency updates built by Noah Warnke, August 31 2016 (no formulas changed).
• Updated by Zoya Kaufmann June 2016 - August 2017
• Merged with older versions by Tanvi Naidu June 19 2017
• Fork, refactor, and creation of CLI and ArcMap interfaces by Christian Gass @ CivicMapper, Fall 2017
• Updates for use within ArcGIS Pro by Christian Gass @ CivicMapper, Spring/Summer 2019
• Additional updates by Tal Cohen 2020