Woody Vegetation on Small Embankment Dams

Transcription

1 Woody Vegetation on Small Embankment Dams Session T2: Current Projects/Small Dams Innsbruck, 22./ Ronald Haselsteiner (FICHTNER GmbH & Co. KG, Turkey)

2 Outline Woody Vegetation on Small Embankment Dams Regulation, Codes, Slovakia 2010 Proposed Bavaria 1999 Bavaria

3 Where are the levees? Wooded dike at River Iller (Bavaria) near Altenstadt with a trail on dike crest (Source: TUM) Complete wooded dike at River Danube near Dillingen in a nature protection area (Source: StMUGV) 3

4 - Plantings Flood protection dike at the river Koeßnach near with poplars and meadow (year 1985, taken from Hacker et al. 1999) Flood protection dike at the river Danube with landside poplar row and waterside bushes and grass/meadow (year 1985, taken from Hacker et al. 1999) 4

5 Woody Vegetation on Small Embankment Dams - Consequences Failed Dike at River Mulde after the flood in the year 2002 Source: Landestalsperrenverwaltung Sachsen 5

6 , Codes & Regulations Technical documents available (Usually free download) USACE, USBR (Free download) TAW (Netherlandes) (Free download) 6

7 , Codes & Regulations Several German regulations DIN 19712/1997 (in revision) BAW MSD (2005) (in revision) (Free download) DWA (DVWK) 210 (in revision) DWA (DVWK) 226 (in revision) 7

8 , Codes & Regulations Possible impacts Holes and damage due to tree failure Increase of permeability Initiation of internal erosion processes Additional static load Hindrance of close sod cover surface erosion Difficulties for maintenance works Hampering of inspection and supervision Harmful effect for other structures (pipes ) Attraction of digging animals tree root gravel 8

9 , Codes & Regulations General Design Criteria In general No woody vegetation, but exceptions No vegetation at overflow sections or spillways Restricted forms of vegetation at the slopes Consideration of hydraulic aspects (floodplains) No woody vegetation within seepage exit Safety corridor Single trees are more harmful than tree groups Removal of trees together with the complete roots 9 Removal or stabilization of embankment if criteria are not met

10 , Codes & Regulations DIN 19712/ DWV 226/1993 Germany Woods withinthedischargesectionmust not decreaseflooddischarge. water level (floodincident) watersideslope (grass) crest (traffic) additional dikebody landsideslope (neglectedgrassland) 3 m berm (traffic) <H/3 10 m 5 m m 3 3 m 1 m 5 m 10 m woods 1) (Poplars>30 m) bushes 1) dikeprotectionzone grasson cm dike bushes 1) dikeroad/ no dikeprotectionzone bushes 1) Woods 1) (restricteduse) Soil toplayer road (Rootsmust not growinto no woods (restricteduse) (Poplars>30 m) (intensive care) staticdikebody. woods no woods no woods no woods neglectedgrassland (extensive care) no woods 1) Plantingshouldbecarriedout in groups. 10

11 , Codes & Regulations MSD BAW (2005) Germany 11

12 , Codes & Regulations Marks & Tschantz (2002) USA 12

13 Proposed Zoning in consideration of project specific constraints U6 U5 U4 Zone 0 U3 U2 Crest road U1 C D1 D2 D3 D4 D5 D6 Reservoir Level m 1 Dam Body n 1 Sealings Filter Uncontrolled Vegetation Controlled Grass, Woods Small Trees Bushes Protection Zone (B) Upstream Slope (depending on reservoir levels and operation) (C) Crest Road (A) Downstream Slope Grass, Small Trees, Bushes Seepage Drainage (A) Protection Zone (B) Grass, Small Trees Controlled Bushes Woods Uncontrolled Vegetation Notes: (A) It is assumed that usually no woody vegetation should come up within these zonings. (B) Within the protection zones restricive utilizations have to be agreed in regard to e. g. agriculture. (C) For temporary reservoirs small bushes and trees can be located on the upstream slopes. The superficial erosion protection has to be considered. 13

14 Proposed Zoning Criteria No impacton stability, operability, serviceability and durability No rooting impact on sealings, drains, filter No harmful vegetation within sensitive areas crest, roads, ways, shoulders, seepage exit Maintenance (annual concept, machinery, costs (!) ) Refurbishment Measures (root barriers, static stability ) Removal of Woody Vegetation (concept, roots ) Interfaces (!): Ecological aspects, recreation, shore stabilization, flood plains, forestry, 14

15 Detailed, project specific assessment of actual conditions in consideration of consequences and vulnerability Continuous maintenance and monitoring is necessary to avoid surprising conditions or refurbishment/removal International (and German) regulations and experience available Balance of landscape, environmental, recreation, etc. aspects Technical (and economical) requirements have to dominate 15

16 Thank you. You pay for your vegetation control concept and maintenance, if you have one or not! 16