Proposed Norwegian classification limits according to morphological modification of surface water bodies

Transcription

1 Proposed Norwegian classification limits according to morphological modification of surface water bodies Brian Glover MULTICONSULT AS with Trygve Hesthagen (NINA) and Eva Skarbøvik (Bioforsk)

2 Objectives and Scope of Study Surface water, including coastal waters The objective is to propose a system for classifying surface waters according to various degrees of hydromorphological impact The product is a propsed set of morhological criteria for delimiting status classes through the measured degree or extent of morphological disturbance (only). The study is to be carried out in two stages: Stage 1 Morhological impacts (draft report in Norwegian) Stage 2 Hydrological Impacts (work not yet started) 2

3 Types of morphological impact reviewed Disturbance of ecological continuity (barriers to fish migrations) Disturbance directly within the water body Rivers (realignments,erosion protection, flood protection works within the river, culverting, extraction of sand and gravel Lakes (disturbance within the litoral zone) Coastal water bodies (disturbace of special natural ecosystem types within shallow water zone down to 10 m depth) Note that hydrological alterations, including regulation of lakes are not yet studied 3

4 Disturbance of ecological continuity Typical barriers Small dams Brook intake structures Culverts and overpasses for roads and railways Landscaping weirs and water level control structures Dry or nearly dry river reaches Fish passes that work badly Simplified approach to non anadrome rivers (similar to Sweden) New proposal for anadrome rivers with man-made barriers to spawning migration 4

5 5 Typical transfer intake structure for hydropower

6 6 Possible to allow fish passage with small modifications?

7 Definition of a barrier to migration Water jump of more than H = 0,5m Smaller than 0,5m water jump with downstream pool depth less than H (preventing fish accelerate) More than 6 m pipe or culvert with high velocity flow (say >10 % gradient) More than 6 m pipe or culvert with a depth of less than 15 cm at normal flow 7

8 Anadrome Yes Evaluate every barrier a/c to definition criteria Divide up all water bodies according to large barriers Decide status classification upstream every barrier a/c to criteria for sea trout Is the river anadrome today? No No Use definition to list large barriers with locations Calculate FG and BE Not anadrome Have there been anadrome fish earlier? Yes No Could it be likely that a new barrier is the cause? Yes Consider status of d/s WB according to possibility to spawn downstream Decide status for the entire water body according to table 2 Status is moderate Evaluate HMWB FG= Degree of fragmentation BE= Barrier effect Figure A - Flow chart for defining class a/c to migration barriers 8

9 Disturbance of ecological continuity in anadrome rivers Criteria determined from abilities of spawning sea trout Status of WB Highest jump in Sea trout that Salmon that Influence on upstream upstream waterlevel (m) can pass can pass migration for spawning H No artificial barrier 0,5 G All spawning fish All sizes White fish can pass. Minnow cannot 1,0 M > 40 cm > 20 cm All spawning fish 2,0 P Few big fish All big fish Spawning salmon can pass 4,0 B None None None 9

10 Disturbance of ecological continuity in non-anadrome rivers (same as in Sweden) Class F-degree B-effect Impact on trout by new barriers to migration H No new barriers to migration in the water body 0 0 G Main river has no impact, only branches or upper part of the river 0 25% M Longest part of the river reduced by less than 25%. Next barrier over the middle. 25% 50% D The longest part of the river is reduced by 25-50%. Next barrier close to the middle 50% 75% MD The longest part of the river is reduced by more than half of the length. Next barrier is very close. 10

11 Disturbance directly within the water body No Group Parameter H G M P B 1 Alteration of river s natural meandering (canalisation, straightening, culverting) Portion of length of WB straightened 0 10% >10-40% >40-70% >70% 2 Alteration of river bed/ substrate (Norwegian proposal) 3b Flood protection works affecting either river bank (not protection bunds exclusively above river banks) Portion of length of WB altered ( Alteration needs defining e.g. more than half of wet section affected?) Portion of combined length of both river banks altered 0 10% >10% 0-5% <5-20% >20-50% >50% (HMWB) 4 Altered natural riverbank vegetation Portion of combined length of both river banks altered 10% >10-20% >20-40% >40-60% >60% 5 Removal or alteration of natural substrate Proportion of substrate affected (at mean flow) 0% 10% >10-25% >25-50% >50% 11

12 Coastal water bodies similar approach to lakes Water Grense body for bordeline vannforekomst New Quay Industrikai Nature ecosystem Naturtype type Verdi A Cvalue Nature Naturtype ecosystem verdi type AA value 10 m kote Nature Naturtype ecosystem verdi B type B value Landfill Utfylling 12

13 13 Shallow water and beach zone altered

14 Proposed classification a/c to weighted modification of natural ecosystem types Status class % of area nature Comments ecosystem affected H Practically no impact 5% G Small degree of impact 15% M Some nature ecosystems affected 30% P Significantly reduced area of important nature ecosystem 50% B Less than half area remains 14