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sitedesign:site_toolbox

GIS toolbox for site design and Permaculture

Besides Hydrological modelling and the Keylines - Lanscape terrain features there are other usefull GIS functionalities we can use in permaculture.

Planting pattern

While dealing with new plantations, we can use GIS to define a regular grid with defied plant distances for then going in the field and plant.

Regular grid on a surface

How to create a regular grid of predefined spacing between points within a defined area :

  • Define the area for the new plantation Qgis → Layer → Create layer → new shape fiule
  • Create a regular grid Qgis → Vector → Regular points function
  • Select points within the new plantation area Qgis → Vector → Geoprocessing → Clip


In the example above, we have selected an area of ~ 0.7 ha, and a planting pattern of 6m distance between plants.

Hedges

How to define an equal spacement between points along a hedge line:

  • Define the hedge line for the new plantation Qgis → Layer → Create layer → new shape (file use line)
  • Import the line in GRASS using
  • Use v.to.points GRASS function to define points within the hedge line

Pond

Different GIS functions could be very useful in desining ponds.

Water accumulation estimates

We have already created a water accumulation layer. Browsing this layer we can query pixels values to select an appropriate location to built a pond. For instance within flat areas we can define a high water accumulation zone. There we can define the extents and draw a sub-basin map of a water basin catchment flowing to a determined location within our site.

  • Define the point of interest querying geographical coordinates from the accumulation map
  • Use r.waters.outlet to create a catchment bassin above the point of interest
  • Overlap the output basin with DEM and river styreams network

The r.water.outlet GRASS gis function settings. We use as input the bassin drain raster map previously created using r.watershed algorithm and N-E geographical coordinates.


From pond site location to water basin definition in GIS. The selected point is connected to a river stream network covering a water basin of 12075 cells of 1mx1m.Knowing the extreme daily rainfall we can project a pond with defined water capacity to store and mitigate flush flooding events.
The following formula give an estimates of the amount of water flowing to a specific location from the upward basin catchment : 100 x rainfall (mm) x catchment surface (ha) x Soil runoff coefficient

We have quantified the catchment surface (ha) using the r.water.outlet function; mm rain and soil coefficient parameters needs to be defined using climatic records and bibliographic references.

Solar irradiation

Sun rise,sunset and sun position

Sun rise sunset calendar Web Processing Service Calendar of sunrise / sunset noon daylight of the sun at any location on the planet for an entire year. The outcomes shows the time and azimuth in degrees.
Sun position at the Summer solstice

Download the Yearly CALENDAR for sunset - sunrise, noon time and sun Azimuth

Topographic shadowing

Hillshade module in Qgis: This calculates the amount of sun or shade for a 3D surface. The dialogue box include options for the sun angle and Hillshade uses a fixed location of the sun to accurately simulate the effects of bare hillside and shaded valleys.

Solar irradiance and irradiation

r.sun function in GRASS gis for Solar irradiance and irradiation model.
This advanced module computes direct (beam), diffuse and reflected solar irradiation raster maps for given :

  • day
  • latitude
  • surface topography
  • atmospheric conditions.

Solar parameters (e.g. sunrise, sunset times, declination, extraterrestrial irradiance, daylight length) are saved in the map history file. Alternatively, a local time can be specified to compute solar incidence angle and/or irradiance raster maps. The shadowing effect of the topography is optionally incorporated.
More info and manual.
Example applications:

Calculation of the integrated daily irradiation for the study site, for the summer solstice, at 1m resolution. Here day 172 (i.e., 21 June in non-leap years):

    r.sun -s dem.farm lin=2.5 alb=0.2 day=172 \\
    beam_rad=b172 diff_rad=d172 \\
    refl_rad=r172 insol_time=it172

Daily irradiation map for the summer solstice:

Terrain Profile

The Qgis plogin profile is able to generate elevation profiles along line features on a Digital Elevation Model. A simple tutorial.
Example of a Profile line on the study site:

sitedesign/site_toolbox.txt · Last modified: 2021/01/20 20:36 (external edit)