BRAT

Step 1 - Input Data

Capacity Model Inputs

The requisite inputs to the capacity model include:

  • A drainage network layer and associated hydrography
  • Vegetation type raster data
  • Digital Elevation Model (DEM)
  • Streamflow (baseflow and peak flow) information throughout drainage network

Existing, readily and freely available datasets from GIS data clearinghouses can be used as model inputs. Just make sure all input data are projected in the same coordinate system prior to running the BRAT model.

Drainage Network

We use the National Hydrograph Dataset (NHD) for the drainage network and associated hydrography data. The NHD layers required to run BRAT include the stream flowline, waterbody and area feature classes.

national_map

Vegetation Raster

You will need 2 separate vegetation rasters:

  • Existing vegetation raster
  • Historic vegetation raster

We typically use Landfire for the vegetation raster inputs. If using Landfire, download:

  • ‘us_140evt’ (existing vegetation type)
  • ‘us_140bps’ (historic vegetation type)

Note: If ‘us_140’ is not yet available for your study area you can use ‘us_130’.

Note: The historic vegetation layer (biophysical settings, bps) represents the vegetation that may have been dominant on the landscape prior to Euro-American settlement and is based on both the current biophysical environment and an approximation of the historical disturbance regime.

landfire

If you are interested in creating your own vegetation raster you will need to make sure all your data points are polygons, and converted into a raster. If possible check to see if any of the LANDFIRE data already has what you are looking for. If you are not mapping all of the vegetation, you will need to merge your vegetation data with the LANDFIRE data. The model will not properly if there are vegetation gaps within your study area. In order for the program to work properly, you will need to add a ‘VEG_CODE’ field to your vegetation input raster. If you are running the entire BRAT model you will also need a land use raster with specific additional fields coded. We tend to use the LANDFIRE EVT raster as out land use raster.

Note: While LANDFIRE data is a good source for existing and historic vegetation in the USA other datasets can be used where LANDFIRE is not available.

DEM

We typically use USGS National Elevation Dataset (NED) 1/3 arc second (~ 10 m) DEM data.

national_map_dem

Streamflow Information

If you need base and high flow estimations for your stream network, regional regression equations can be found at USGS StreamStats or USGS National Streamflow Statistics.

  • Baseflow regional regression equations (e.g. PQ80 for month with lowest flows)
  • Highflow regional regression equations (e.g. Q2 - 2 year recurrence interval peak flow)

Potential Conflict Model Inputs

The requisite inputs to the potential conflict model include:

  • Approximation of the valley bottom
  • Detailed roads layer
  • Railroads layer
  • Canals layer
  • Landuse raster

Valley Bottom Layer

The valley bottom is a polgon feature class. We use it to check if roads or railroads are in the valley bottom as they may have a higher probability of being flooded or impacted by nearby beaver dam building activity. The Valley Bottom Extraction Tool (V-BET) is what we typically use to derive this.

Roads Layer

We use TIGER roads shapefile for the roads layer input. Use ‘All Roads’ shapefiles which are downloaded by county.

Railroads Layer

The national railroads shapefile can by downloaded here.

Canals

Canals can be extracted from the NHD Flowline layer (our recommended drainage network dataset) using the ‘FCODE’ attribute field. Canals have ‘FCODE’ 33600, 33601, and 33603.

Land Use Raster

If no accurate land use layer exits for you study are you can use the Landfire existing vegetation type raster (e.g., ‘us_140evt’).

Continue to Step 2

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