There is a thing
called natural contours of the land
it slopes and dips and curves this way and that
around here
with the uplift of tectonic plates
flowing rivers
and up down of the seas
there is not a whole lot of just plain flat land
it goes high low everywhere

in olden times
that bottom spot where the water gathered
would be mostly rushes and sedges, and a sprinkling of horsetails and ferns
on the sides of the hills would be coyote bushes and their friend sticky monkey flower
as you reached the drier well drained ridges
that might turn to grasslands of lupines, and outcrops of sedimentary red rocks

As people settle
they prefer flat usable space to walk on, to place a table on
they want to build a house that is not tilted
a house with a proper foundation
so they move the dirt and rock around
and change the grade from a slope to a level one
the places around town that were too steep or wet to build on, they left them
until the engineers could catch up with 15’ tall rebarred retaining walls
heavy equipment
and pile drivers going deep into the rock
to hold back the dirt that wanted to fall down
dirt that wanted to recline and rest into a relaxed repose

if you build a retaining wall
you cut the soil away, erect a wall, and fill in the pockets behind it
you want to make sure the wall is strong and does not tumble forward
due to the weight of the soil and water
in dry times that soil seems somewhat stable
but when wet it becomes a fairly dynamic weight load
and will collapse that wall in a second
if the wall is not well anchored and sunk deep
if the wall does not have some way to release the pressure building up behind it

another way around the same problem of flat usable space
is to go above ground, not below it
so you pour some concrete footings or piers
attach some wooden posts to em, and go high
this way you do not have to do much excavation
and the water falls in between the deck lumber to the earth below
and keeps going down the hill
while you can sip your morning brew and enjoy your piece of pastry
on the nice level redwood deck

Look around and you will see lots of slopes
and how we have transformed the landscape
to make it fit our lives
plumb and level, flat consistent and regular
horizontal and vertical, not diagonal

To navigate the levels, you still need to get from one to another
the usual method is make stairs or ramps
indoors, architects have a recipe for how big the steps are, and how high each step is
tread is where you place your foot, rise is the height between the steps
2R + T = 26, R is rise, T is tread
so if your tread is 12”, your rise is 7”, and so on, this is about middle ground average fit
if your feet are 14” long, then you want a bigger tread than that
obviously you would not want a tread that is 4”, and a rise that is 11”…
you do not want just the tip of your foot on that step

Also, you want the step rises to be consistent as you walked up or down the stairs
nothing trips up a person more than a step with a rise of 2”, then 4”, then 3”…
its not an obstacle course you are building, just a way to get from one elevation to the next

in the landscape, you do not always have to follow the architect’s indoor recipe
you can have a long sinewy gentle set of stairs, each with a two foot tread, and two inch rise
stairs that wind slowly down to the lakeside
you can have stairs that double as seats, serving as an amphitheater for the performance in the garden below
or you can have a set of stairs like in the japanese garden of golden gate park, with a rise of over 12”, in order that you pay penance and suffer before your reach the top that is a pagoda or a shrine
so the goals, and hence the rules, in the garden are a bit more flexible and variable also
we are not as constrained or rigid or boxy
as far as stairs are concerned

To measure the slope its pretty basic
the rise over the run gives you a number
so for example, sewer pipes in the house, plumbers lay that pipe with a pitch of 1/4” per foot
that way dish water and poop run out the house, and do not sit there
so 1/4” over 12” (one foot) is…
take out the calculator
.0208333333, that is around .o2, that is a 2% slope
you can express the slope as a number, or a fraction, or as a percentage
you can express in in degrees also
say, a forty five degree slope is a rise/run ratio of 1:1, or 100% slope
it dont matter, the numbers and names change but the slope is the same
if you are in town and looking for a steep street
go to 22nd Street between Church and Vicksburg in Noe Valley
that is a slope of .315, or 31.5% slope, looks like a roller coaster