Friday, April 14, 2017

Tables for Island Dimensions and Population

Here's a rough draft of some tables to generate random islands.  This is just the basic geography and demographics.   More adventure-centric tables are on the way soon, for when you already know what an island looks like and where it is, and just want some ideas of interesting stuff to put on it.

A term used on the tables is "high island".  This is the default island type we think of most of the time when we hear the word "island".


01-05  Stack*
06-30  tidal island**
31-100 island
*Stacks are >= 1 sq mi but are usually found in numbers of 3d18
**As per regular small island (roll on (roll on small island type tables for appropriate climate at a -10% penalty) but connected to mainland at low tide; tidal islands are only very rarely more than 200 sq mi)

01-05  seamount**
06-100 island
*  There are no seamounts in inland seas
** A seamount is submerged and considered as no result if encountered by skilled captain in a shipping lane as it will be charted, but may be sufficiently shallow to imperil shipping if uncharted or inexperienced (possible 5% chance sunken village/town/city on its surface; double if uncharted).

Island Climate Zone
01-20  Frigid
21-60  temperate
61-75  subtropical
76-100 tropical


Regular Island Class percentages based upon ratio of islands known, not total
01-80  Small Island (or Islet)
90-100 Large Island

Small Island Area
01-40  <= 1 sq mi
41-65  1-10 sq mi
66-85  11-100 sq mi
86-100 101-400 sq mi

Large Island Area
01-29  400-1,000 sq mi
59-78  1,001-2,000 sq mi
79-85  2,001-4,000 sq mi
86-91  4,001-10,000 sq mi
92-97  10,001-40,000 sq mi
98-100 40,001+ sq mi

Length/width (all ratios approximate) (modified by Table 1.A)

01-05   7:1
06-10   10+:1
11-25   5:1
26-45   3:1
46-70   2:1
71-100  1:1 (or virtually equal)

Table 1.A size modifiers for L/W
-10 up to 10 sq mi
+10 >400 sq mi
N/A all others

Island Shape*
01-10  irregular
11-14  A or V
15-26  B
27-31  C or G
32-40  D
41     E or F
42     H
43-45  I or T
46-48  J
49     K
60-62  L
63     M or W
64     N or Z
65-85  O or Q (the classic)
86-88  P or R
89-90  S
91-96  U
97     X
98-100 Y

* If a letter is rolled, the intent is a rough inspiration in the general shape; either capital or small version, in any orientation; deform as necessary for a non-obvious result.  If random orientation is required, roll 1d8 for compass point with standard letter orientation used on a result of "1" (true north) and rotating clockwise.

All large islands are high islands
Small frigid and temperate island type (modified by Table 1.B)
01-05  rocky*
05-40  skerry or ait**
41-60  sandbar or barrier**
61-100 High island***

Small sub- and tropical island type (modified by Table 1.B)
01-15  atoll** (can't be tidal islands)
16-25  rocky*
26-40  sandbar or barrier**
41-60  cay or key**
61-100 High island***

*     rocky islands have no groundwater, but may have captured rainwater
**    40% chance of fresh groundwater if between 11-100 sq mi, otherwise none
***   40% chance of fresh groundwater if between 1-10 sq mi; 80% if 11-25 sq mi; 100% <25 sq mi
****  groundwater may be frozen
***** chances presume island is within a body of salt water;ground water is always present at freshwater islands

Table 1.B size modifiers for type
-35  <= 1 sq mi
-10  1-10 sq mi
N/A  11-100 sq mi
+40 101-400 sq mi

island is active volcano (high islands only)
01-20 yes
21-80 no

years since last significant eruption
01-25  currently active
26-75  within 1-100 years ago, active often
76-90  within 1-100 years ago, inactive often
91-100 between 100-1000 years ago

eruption potential (with example)
01-30  effusive             hawaii
31-50  gentle                stromboli
51-65  explosive          etna
66-80  catastrophic       lassen peak
81-90  cataclysmic       pelee
91-95  paroxysmic       vesuvius
95-97  colossal             krakatoa
98-99  super-colossal   tambora
100    mega-colossal    yellowstone  

High island max elevation
01-50  up to 500'
51-60  between 501 and 1000'
61-70  between 1001' and 2000'
71-80  between 2001' and 4000'
81-90  between 4001' and 8000'
91-100 between 8001' and 16000' (or higher at DM choice)

all other island types (OIT) max elevation (modified by Table 1.C)
01-25   1'-10'
26-50  11'-50'
51-90  51'-100'
91-100 101'-250'

Table 1.C OIT max el modifier
-50  sandbar or barrier
-10  atoll
N/A  rocky
+20  cay or key

Vegetation/fertility (modified by Table 1.D)
bare rock is always "none"

01-15  no vegetation
16-30  very little, non-edible
31-60  occasional plants, some edible
61-85  varied vegetation, many edible
81-90  cornucopia
91-100 rain forest

Table 1.D size and other modifiers for Vegetation (cumulative)
-35  <= 1 sq mi
N/A  1-10 sq mi
+10  11-400 sq mi
+40  400+ sq mi
+25  between 1001' and 2000' max el
+50  volcanic or 2000'+ max el

creatures present? (modified by Table 1.E)
01-10  No creatures
11-20  one dominant animal species makes non-permanent use (e.g., seal rocks)
21-40  1d4 bird* or sea-based animal species, no predators (animals likely don't react to danger)
41-60  bird* and sea-based animal species, plus a prey/predator combo**
61-80  bird* and sea-based animal species, with varied land animals/monsters
81-100 complex ecosystems
* 20% chance bird species are flightless
** a predator has a 50% chance of being either an animal or a monster

Table 1.E modifiers for creatures present by vegetation type
-60  no vegetation
-50  very little, non-edible
-30  occasional plants, some edible
N/A  varied vegetation, many edible
+40  cornucopia
+60  rain forest

populated?* (modified by Table 1.F)
*any cornucopia or rain forest island is always populated, if not by people than by organized monsters, unless the DM rules otherwise

01-30   never
31-60   formerly
61-100  currently

Table 1.F modifiers for populated by vegetation type
-60  no vegetation
-50  very little, non-edible
-30  occasional plants, some edible
N/A  varied vegetation, many edible

inhabitant spread (modified by Table 1.G)
01-50   single village/town*
51-75   one tribe/nation - no organized monsters
76-90   multiple tribes/nations - no organized monsters
91-100  one (50%) or many (50%) tribe(s)/nation(s) and organized monsters*
* note at DM choice this could be an aquatic race in the immediate vicinity (unfriendly if an organized monster)

Table 1.G modifiers for inhabitant spread by island size*
-25  1-10 sq mi
N/A  11-100 sq mi
+50  101-400 sq mi
* all islands =< 1 sq mi have only a single village/town, if any

Population are*
01-60  native(s)
61-70  nearby group; settling colonists
71-85  nearby group; economic and/or military outpost
86-90  far away group; settling colonists
91-100 far away group; economic and/or military outpost
* For quantity, roll either on the town population chart, or number appearing if determination by monster entry is more appropriate

Population migratory/temp or permanent?

01-10  migratory; passing through
11-40  migratory; regular circuit
41-50  mix of migratory and settled if more than one group; DM details*****
51-100 permanent
population split if mixed
01-30  about even
31-70  either permanent or temp is (possibly cumulatively) 2/3 of the pop, the other 1/3
71-100 lopsided one way or the other

Rivalry if multiple groups? (modified by Table 1.H)
01-50  yes
51-100 no

Table 1.H rivalry island size modifier*
-25  1-10 sq mi
N/A  11-100 sq mi
+40  101-400 sq mi

Population group technology compared to AD&D standard
either roll as general status of all groups on the island, or roll for each group
01-50  more primitive
51-95  normal
96-100 more advanced* (75% chance forgotten/hiding civilization)
* advanced groups are always permanent, but never colonists if forgotten/hiding; reclassify as necessary

geographic features*
**0-2  <= 1 sq mi
  0-3  1-10 sq mi
  2-4  11-400 sq mi
  3-6  400+ sq mi
*for larger islands, consider as the number of features within 25 sq mi of landing site; detail as necessary for campaign play
** roll 1d4; rolls of 3 or 4 equal 0 features. for islands of this size, it's first feature type will always be a (sole) cove

Feature Type
01-05  bay
06-10  caves
11-15  corrie loch**
16-20  coastal cliffs
21-25  inland cliffs
26-30  cove (hold 1-2 ships)
31-35  delta
36-40  harbor
41-45  hills
46-50  internal body of water equal to 10%-50% of total area**
51-55  loose scree of various size (75% chance good catapult ammo here)
56-60  major stream or river**
61-65  peninsula (20% chance of fort if appropriate pop and tech)
66-70  pool**
71-75  prominent peak
76-80  promontory (50% chance of fort if appropriate pop and tech)
81-85  quarry-quality rock
86-90  swamp
91-95  thicket/forest
96-100 waterfall**
*reroll features incompatible with known island characteristics
** in frigid climates, consider results as glacial activity of appropriate size

Do treasure maps lead to this island?
01-10  yes, for good reason
11-50  yes, somewhere one does but the treasure's gone
51-100 no

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