(Geomorphology)

A landscape drainage pattern where tributary streams generally run perpendicular to the streams they empty into, forming a stream network that vaguely resembles the way that vines grow on trelliswork.

Trellised drainage systems generally form when the underlying geology of a landscape undergoing uplift tends to form long parallel ridges separated by long parallel valleys, such as a ridge and valley landscape formed by folded mountains, or a cuesta landscape formed by gently sloping layers of sedimentary rock.

As the landscape develops, some streams are able to cut across the ridges, forming principal consequent streams which carry water out of particular valleys. Parallel to the ridges form subsequent streams, carrying water and sediment into the consequents.

An aerial view of a landscape with trellised drainage might look like this:

   {     /               }          |                      {                 \
  _}    |               {          /                        }                /
 {      |               }          |                       {                |
  }     |              {           |                       _}               |
 ~~._   `--             }          |                      {                 |
     >=========._ CON- {           \                       }                |    
    /  ,--    `~==========._   SE- `--                   {                  \
   {  |                   }`~===============._    -QUENT  }                   \
   }  |                  {         ,--      `~===================._            `--
   {  \                  }        /                            {{`-=========================
   }  /                 {        |                             }}            .-----
  {  |                 _}        \                          S {{_           |
  }  |        rese-   {          /               }          U   }}         /
  {   \      ~~~~~~~~.}         |               {           B  {{         |
   }   |     quent   {          |               _}          S   }}       /
  {     \__           }         |          ~~._{            E  {{_      |
   }~~~'___)         {          |               `~~~.__      Q   }}     |
  {    /              } ob-     `--._                  >~~~~~==={{      |
 _}   |              {_.~~~~~~     __)                {_     U   }}     |
{     |               _} sequent  /                     }    E  {{_     |
 }    /              {           /                     {     N    }}    |
{    |                }         |                      _}     T  {{     |
 }   |               {          |                     {           }}    |
{    |                }         |                     _}         {{_    |
_}   /                {         |                    {             }}   |
    |                _}         |                     }           {{     \
    |               {           |                    {            _}}     \
    |                }          \                     }          {{       |


Occasionally, you will see special terms used for branch streams of subsequents: "resequent" for a stream flowing in the same direction as a consequent, and "obsequent" for a stream flowing in the opposite direction from the consequent. These terms don't have any particular significance, however, and you should stick to "consequent" and "subsequent".

Log in or register to write something here or to contact authors.