Wetlands in River Valleys as an Effect of Fluvial Processes and Anthropopression - Wetlands and Water Framework Directive: Protection, Management and Climate Change - page 67

5.2 Case Study

5.2.1 Fluvial Processes in Natural Rivers

Rivers always tend to develop a well balanced channel (Bartnik and Ksi ąż ek 2007 ;

Bartnik et al. 2007 ; Ksi ek et al. 2010 ). Even if there is a scarcity of the trans-

ported material, the adequate longitudinal and cross-section pro

ąż

les of the river

ż ń ż

channel can be found (Korpak et al. 2009 ; Stru ga et al. 2009 ).

The curvature of natural rivers increases proportionally to the transported load
alimentation and inversely to the slope of the river.
Mountainuous and lowland rivers differ in the

y ski 2014 ;Wy

fl flow dynamics as well as the

intensity of fluvial processes. The sources of differences are connected to the

retention and slopes of the basin but also to the size of transported material.

fl

Lowland Rivers
Natural rivers modify their channels and valleys due to the

fl fluvial processes

appearing the whole year. The highest activity of the fl flowing water on channel

creation appear with the quite low dominant low which can be valued by the Q 75%

(Leopold and Wolman 1957 ; Radecki-Pawlik 2011 ; Stru

fl

ż y ń ski et al. 2013 ). These

fl flows modify morphological parameters of the channel due to the bed and bank

erosion or accumulation of bed material and contribute to the channel natural
mobility (e.g., meandering, wandering) (Church 1992 ; Rosgen 1994 ). Dramatic
channel

transformations of river runs are very likely to occur during fl oods.

Ł

According to the historical data gathered by ajczak ( 2006b ) on the Nida River, the

multichannel system of lowland river can steadily change (Fig. 5.1 ).
Pictures describing the river system in the given years reveal the high hydro-
morphological dynamics. Such an activity is frequently recorded in alluvial chan-
nels. Two mechanisms may appear in lowland rivers during fl floods. One is creating

(a) (b) (c)

Fig. 5.1 Historical data show numerous changes of the Nida River morphology (after Ł ajczak

2006a ). a 1839, b 1916, c 1938