Re: Swale design
Hmm... I like the topic... but don't have much concrete experience to offer (never stopped me yet).
I guess if your already ripping, digging and maintaining swales sounds like work, so I'd say you'd want to achieve the desired effect with as few swales as possible. So then it comes to the goal. If the goal is percolation, I bet it would matter a lot how fast your 1.1m of rain comes? Does the sky rip open and dump (more swales), or does it drizzle forever (ripping is good enough). is the goal to create moist microclimates for select species? then you'd be trying to concentrate good sources of water, and then if you are intercropping between swale/tree/hedge rows, then what spacing do you need to intercrop. Is the swale tree row about wind effects? Are you using swales to deliver water? a different issue. Form follows function... in short I'd inventory the "why" of your swales to figure out the factors that should determine spacing.
Distance between swales = (volume of swale * soil permeability)/(steepness * rate of rainfall)
or.. distance between swales decreases as slope and rainfall rate increases and ability of soil/swale system to absorb water decreases.
Olympia, WA, USA