Storm surge protection of the Limfjord: Closure of Thyborøn Channel

Student thesis: Master thesis (including HD thesis)

  • Johny Dilan Antony
  • Max Jacob Friis
  • Kåre Bjerre
4. term, Water and Environment, Master (Master Programme)
This project is based on the storm surges in the Limfjord in Denmark. It has been found
that the water level within the fjord can cause floods of the lower regions of the coastal
areas. The majority of these areas are of agricultural nature, wherefore the focus areas
of this report is the cities where floods often occur. The cities that have been chosen are
Løgstør og Skive.
The first part of the report describes where the location of the project is, and the problems
that have been in the past. Furthermore this part describes the solutions, which the Danish
Coastal Authority has found to lower the water level during future storm surges.
This introduction leads up to the first part of the report, where the water level is described
with two different models. These models are afterwards used to simulate different solutions
from the introduction, where three solutions have been chosen; expansion of groyne 59,
just outside Thyborøn Kanal in the western part of the Limfjord, expansion of groyne 63
within Thyborøn Kanal and a dam with a water gate. The best solution is then used to
estimate its effects on water levels in the future with climate changes. It is found that
the dam with a water gate is the best solution, and that it will reduce the extreme water
levels during storm surges, even in the future with climate changes.
The second part of the report focuses on the water quality in the Limfjord, since
the ecological water quality is found to be poor in a majority of the fjord. This part
simulates the solutions found in the previous part in order to estimate there impact on
the water quality, and the solution from the environmental plan for the Limfjord. The
solution recommended in the environmental plan for the Limfjord is a reduction of the
nutrient input. The simple model returned a slightly worse water quality, but the more
advanced model returned a better quality. The solution from the environmental plan could
potentially change the water quality to a higher EQR that it is now. Additionally a simple
model for the sediment in the fjord is built in order to estimate the changes of the seabed,
with the habitat depth of eelgrass as the focus area, however this is found to not change
considerably with any of the solutions from the Danish Coastal Authority in question.
The conclusion of the report is that the solutions for lowering the extreme water level
all will have a positive impact on the water level, and that they could have a positive
impact on the water quality in the waterbody. Therefore it is found that a combination of
suggested solutions for the Limfjord is the best solution. For the water level a dam with a
water gate is the best solution, even when taking the future water rise in to the equation,
while the best solution for the water quality is to reduce the discharge of nutrients into
the fjord.
LanguageDanish
Publication date9 Jun 2016
Number of pages138
ID: 235031703