Deltas on the move; Making deltas cope with the effects of climate c

KvR report 001/2006Figure 6.12: <strong>Deltas</strong> ranked for adaptation, based on the slope of subaerialcoastal plain (slope on land).LenaOrinocoGanges-BrahmaputraPoMahakamRedMekongParanaNileMississippiChao PhrayaFlyZambeziHuang He (Yellow )Yangtze-KiangMacKenzieMagdalenaGodavariMahanadiDanubePechoraShatt el ArabSao FranciscoYukonKrishnaIndusBurdekinDneiperSenegalEbroIrraw addyFrazerNigerMangoky0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9slope coastal plain (degrees)The Lena delta (Hart &Coleman, 2004) ranks ashighly suitable foradaptation because of itslow sloping (1,1 %) coastalplain. The low slope iscaused by various physicalfactors. Discharge of theLena River is extremelyhigh. It abruptly increasesfrom 5.578 m 3 /s in May to amaximum of 73.997 m 3 /s inJune, when spring meltbegins. Nearly every year inthe late spring, ice blocksthe flow of water at themouth of the Lena River in north eastern Russia and gives rise to floods across theSiberian plains, because water upstream thaws earlier than water at the mouth of theriver. Close to the apex of the delta, the Lena River cuts through broad coastalPleistocene terraces. As a result the fan-shaped delta covers some 43.563 km 2 andis a maze of small distributaries. The delta located in sparsely populated NorthEastern Siberia (see also Figure 6.13).<strong>Deltas</strong> on the moveNo intervention as a sustainable approachSurprisingly many deltas have a comparatively low population density: here the lastoption of a system-based approach, i.e. taking no measures, would be quite feasible.Most suitable for doing nothing, based on coastal population density, are thefollowing deltas (Figure 6.13):1. Lena;2. MacKenzie;3. Yukon;4. Fly;5. Burdekin.The first the deltas are located at high latitudes, the Fly and Burdekin are relativelysmall deltas (see Figure 6.10, delta area).Figure 6.13: <strong>Deltas</strong> that are particularly suitable for doing nothing based on coastalpopulation density.LenaMacKenzieYukonFlyBurdekinPechoraMangokyMississippiMahakamOrinocoZambeziParanaShatt el ArabSao FranciscoEbroDneiperIndusMagdalenaPoIrraw addyNigerDanubeSenegalMekongHuang He (Yellow )MahanadiKrishnaGanges-GodavariYangtze-KiangNileRedChao PhrayaFrazer0 500 1000 1500 2000 2500 3000coastal population density (N/km2)6.4 <strong>Deltas</strong> in the next phaseOne of the objectives of phase 1 was to come up with a list of deltas that might beinteresting for the next phase. Carefully examining the correlations betweenvariables describing the deltas (in the Annex), defining indicators for physicalvulnerability, stock at risk, and potential for system-based approaches (in Table 5.4),and subsequently ranking the deltas (section 6.4) provides the firm grip and thoroughunderstanding need for such a selection. Nonetheless, we would like to stress thatwhether a delta is interesting or not for phase 2 is context and scale dependent.6869