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Retention potential in river headstream areas

Author(s): Jan Kocum, Bohumír Janský
Charles University in Prague Faculty of Science Department of Physical Geography and Geoecology Albertov 6, 128 43 Prague 2, Czech Republic phone: +420 720 303 030, +420 221 951 350 fax: +420 221 951 367 email: kocum1@natur.cuni.cz

Keyword(s): retention potential, peatbogs hydrological function, flood protection, headstream area, ultrasound water level gauge, peak flow, drought

Article:

Poster:

Session: OS4g Risk management 1

AbstractIn context of catastrophic floods

and extreme droughts in recent years there is an urgent need of solving of flood protection questions and measures

leading to discharge increase in dry periods, not using just classical engineering methods but also untraditional

practices. There is a new strategy focusing on gradual increase of river catchment retention capacity including the

realization of measures as runoff retardation and water retention increase in headstream areas.
To increase water

retention in Vltava River headstream area (southwestern Czech Republic), the source area of a number of

catastrophic flood events in recent years, the detailed analysis of peatbogs hydrological function and qualified

reference of measures being implemented at present by the Bohemian Forest National Park Management in

connection with former ameliorative channels (made during communist regime) dyking need to be done. The

peatbogs influence on runoff conditions is being assessed by detailed comparison of hydrological regimes in two

subcatchments with very different peatland proportion. We can reason about the peatbog influence on hydrological

process also with respect to its affecting of water quality, respectively to ionic structure of water in periods of high or

low discharges.
Very favourable conditions for realization of this project currently bear on existence of several

water measure profiles with long time series and on using modern equipment and methods including a number of

automatic ultrasound water level gauges and shuttle precipitation gauges. Our department can also go upon results of

bog pools detailed research that has been carried out in recent years. Thorough analyses of extreme runoff ascending

and descending phases carried in profiles closing several subcatchments with different geographical conditions show

higher amount of peak flows and their shorter reaction to causal amount of precipitation in the case of highly peaty

areas, therefore more distinct runoff variability of streams draining peatland localities. As well, detailed analysis of

snow conditions in the study catchment as an important component of rainfall-runoff process is carried out by means

of aerial photographic surveying for monitoring of snow cover thickness and of hydrometers for water value

determinations.
The problem of the peatbogs hydrological function has not been so far fully solved despite a

number of domestic and foreign projects and broad debates among experts. It depends on a number of factors

considering the type of a peatland, its health state, its rate of anthropogenic impact, etc. In addition to considering the

renewal respectively dyking of former channels draining peatbogs we should consider also evaluation of possible

former accumulative reservoirs (used for wood floating in former times) restoration which could function for example

as dry (green) polders. Using complex system of hydrological models such as rainfall-runoff and routing models with

semi-distributed approach we could be able to simulate the runoff process in the source area and to assess the

effectiveness of these small accumulation reservoirs. By implementation of these unforceable measures realized in

river headstream areas we could contribute to reduction of peak flows and to increase of water resources during

extreme droughts in future.

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Retention potential in river headstream areas