Wetland Land Use Management at Whole Catchment Scale (WP5.3 and WP5.4) Professor Ian Cluckie College of Engineering Swansea University 1

Wetland Land Use Management at Whole Catchment Scale – WP5.3 The Parrett and Tone catchments – Large floods in 1999 and 2002 DHI MIKE SHE Model Soil & Mud Flow Soil Compaction Run off / Wash off

Human Activities and Soil 3 Soil degradation increased by heavy machinery or soils worked in wet conditions Cultivated land, winter cereal crops, more degraded than permanent grass, but it varies with the degree of slope Land Use Bare soil: harvest ~ before seeding Average Soil Moisture Deficit (1961 ~ 2000) If soil moisture is at optimum levels during the soil cultivation periods of the autumn and spring the risk of soil degradation occurring is limited

Flood Impact Downstream? 4 LAND USE Change had relatively LITTLE impact at Whole Catchment Scale FLOOD retention STORAGE MORE EFFECTIVE at decreasing flood volume and peak, but varied by sub- catchment Large Catchment dominated by CHANNEL NETWORK

5 Lowland Sediments WP5.4 - Tone Catchment Case Study Sediment delivery to rivers is likely to be exacerbated by future climate change Uncertainty how sediment drives changes in morphology and flood risk in lowland rivers – Highly Event Driven RBMP & CFMP targets & activities must not conflict, and preferably support each other

Sediment Issues: contact: 1.Wash load sediment can alter morphology in key locations 2.Water level and inundation patterns likely to be affected, but flood risk impacts may be minimal 3.River sediment management (receptor) may be restricted to local ad hoc intervention to maintain flood defence assets or other uses – e.g. Dredging 4.Catchment sediment management (source) likely to be driven by WFD & Soil Resource Protection rather than FRM 5.Areas of uncertainty include defining sediment yield and understanding temporal position in a river regime

Key Messages 7 The impact of land Use Management was NOT significant at Whole Catchment Scale – FLOODPEAK and VOLUME However,was important at plot and Field Scale! Space/time scaling effects are still not completely understood BUT dominance of Channel Network primary control on Flood Impact on Large Catchments Land Use Change had greater impact on Sediment, Bio-Diversity, Water Quality and Landscape rather than flood peak or volume FRM still important but NOT Panacea!