Översvämningskartering av Vombs ängar

Sammanfattning

Vomb meadows is an area well knows for its rich bird life. During the 19:th

century until mid 20:th century, the meadows were flooded annually in order to

increase the hay yield. The river Klingavälsån situated along the west side of the

meadows, used to be a shallow river, meandering across the landscape. In the

1940?s the river was straightened and made deeper. This was done in purpose of

draining the area around the river, thus enabling agriculture. The effects were that

Vomb meadows dried up, and many of the popular bird species disappeared from

the area.

Today the meadows are flooded again. The municipality of Lund has in a project

during 1999 and 2000, re-dug part of the river. It has through this regained the

former shallow bottom and the meandering shape; now flooding at 3 m3/s instead

of the earlier 6 m3/s. As a consequence, the groundwater level has also been

raised.

The result of the project has been evaluated by mapping the extent of the flooding

and comparing these maps with the flow in Klingavälsån. Three maps have been

made and the flow has been measured on five different occasions.

The spring of 2002 had a lot of precipitation and the meadows were flooded

during long periods. The floods were relatively evenly distributed over the

meadows. Water was mainly concentrated around ditches and in the northern part

of the meadows where the ground level is flatter and lower. The flooding varied

with the flow in Klingavälsån, thus depending on the precipitation. The high

flows have also created erosion in the brinks of Klingavälsån, creating good

possibilities for a continuing natural meandering of the river. The flows of the

magnitude that took place this year in Klingavälsån are calculated to occur around

every ninth year.

There are other measures to increase the flooding of Vomb meadows. To decrease

the groundwater gradient, dams can be built in the river. Big stones and rocks

placed in the river channel decrease the velocity of the river and therefore also its

drainage capacity, thus leaving more water standing on the ground surface.

Channels can be dug from the river in to the meadows, increasing the supply of

water when the level of the river is high enough.